Renal effects of selective cyclooxygenase-2 inhibition in normotensive salt-depleted subjects.

PURPOSE: To compare the renal hemodynamic and tubular effects of celecoxib, a selective inhibitor of cyclooxygenase-2 (COX-2) to those of naproxen, a nonselective inhibitor of cyclooxygenases in salt-depleted subjects. METHODS AND SUBJECTS: Forty subjects were randomized into four parallel groups to receive 200 mg celecoxib twice a day, 400 mg celecoxib twice a day, 500 mg naproxen twice a day, or a placebo for 7 days according to a double-blind study design. Blood pressure, renal hemodynamics, and urinary water and electrolyte excretion were measured before and for 3 hours after drug intake on days 1 and 7. RESULTS: Celecoxib had no effect on systemic blood pressure, but short-term transient decreases in renal blood flow and glomerular filtration rate were found with the highest dose of 400 mg on day 1. On the first day, both celecoxib and naproxen decreased urine output (P < .05) and sodium, lithium, and potassium excretion (P < .01). On day 7, similar effects on water and sodium excretion were observed. During repeated administration, a significant sodium retention occurred during the first 3 days. CONCLUSION: In salt-depleted subjects, selective inhibition of COX-2 causes sodium and potassium retention. This suggests that an increased selectivity for COX-2 does not spare the kidney, at least during salt depletion.     

Inhibitors of cyclooxygenase-2, but not cyclooxygenase-1 provide structural and functional protection against quinolinic acid-induced neurodegeneration

Cyclooxygenases (COXs) are implicated in neurodegenerative processes associated with acute and chronic neurological diseases. Given the potential utility of COX inhibitors in treating these disorders, we examined the nonselective COX inhibitor flurbiprofen, the specific COX-1 inhibitor valeryl salicylate (VS), and the COX-2 inhibitor N-[2-(cyclohexyloxy)-4-nitrophenyl]methanesulfonamide (NS-398) for their abilities to protect striatal neurons against a quinolinic acid (QA)-induced excitotoxic lesion. Rats were administered COX inhibitors 10 min before a unilateral QA lesion of the striatum, and then tested 2 to 3 weeks later in a battery of motor tasks (bracing, placing, akinesia, and apomorphine-induced rotations). Lesion volume was assessed using immunohistochemical methods 1 month after lesioning. Orally administered flurbiprofen (50 mg) was highly neuroprotective, preserving 84 to 99% of motor performance (ED50 = 8.6-9.7 mg) while reducing lesion volume 75% (ED50 = 3.2 mg). The identities of the COX isoforms associated with QA-induced neurodegeneration were determined using VS and NS-398. Oral VS was ineffective in virtually all indices of functional neuroprotection. In contrast, oral NS-398 was highly effective, preserving approximately 83% of motor performance at2mg(ED50 = 0.1-0.4 mg), and reducing lesion volume 100% (ED50 = 0.4 mg). Similar results were obtained using inhaled flurbiprofen (2 mg), which preserved 88 to 100% of motor performance while reducing striatal lesion size 92%. These results demonstrate that COX-2 inhibition protects neurons from acute, excitotoxic neurodegeneration. Moreover, formulating a nonselective COX inhibitor into an inhalable preparation dramatically improves its potency in treating acute neuronal damage, a situation where the rapidity of drug delivery and onset of action is critical to clinical efficacy.     

Cox-2 inhibitor attenuates NO-induced nNOS in rat caudal trigeminal nucleus

OBJECTIVE: The aim of the present study was to determine which isoform of the cyclooxygenase (COX) enzyme plays a role in the neuronal nitric oxide synthase (nNOS) activation caused by nitroglycerin (NTG), in the most caudal part of the trigeminal caudal nucleus (TNC) of the rat. BACKGROUND: Nitric oxide donor, NTG, can trigger migraine attack in migraineurs, but not in healthy persons. In rats, subcutaneous administration of NTG (10 mg/kg) increases significantly the number of nNOS-immunoreactive neurons in the TNC after 4 hours, which could be attenuated by acetyl-salicylate (Aspirin), a nonselective COX-inhibitor. METHODS: SPRD rats were divided into 3 groups: (1) control group (no drug administration), (2) NS398 (selective COX-2 inhibitor) administration (1, 3, or 5 mg/kg), and (3) SC560 (selective COX-1 inhibitor) administration (1, 5, or 10 mg/kg). Thirty minutes after drug administration, the animals received NTG (10 mg/kg) or placebo injection. Four hours later the animals were transcardially perfused and the cervical part of the TNC was removed for immunohistochemistry. Results.-The selective COX-2 inhibitor NS398 in contrast to the selective COX-1 inhibitor SC560 attenuates the NTG-induced nNOS expression dose-dependently. CONCLUSION: These findings suggest that metabolites deriving from COX-2 (but not COX-1) may be the most important factors in the NTG-induced nNOS expression. These data could help to better understand the pathogenesis of headaches and the action of antimigraine drugs.     

Adaptation to increased dietary salt intake in the rat. Role of endogenous nitric oxide.

Previous studies have suggested that nitric oxide (NO) plays a role in regulation of renal vascular tone and sodium handling. We questioned whether the effects of NO synthase inhibition on renal function are direct or due to increased renal perfusion pressure (RPP) and whether stimulation of endogenous NO activity plays a role in adaptation to increased dietary salt intake. Intrarenal arterial infusion of the NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) in control rats resulted in decreased glomerular filtration rate, renal vasoconstriction, natriuresis, and proteinuria. When RPP was held at basal levels with suprarenal aortic snare, L-NMMA had similar hemodynamic effects but decreased sodium excretion and did not induce proteinuria. Exposure of rats to high salt intake (1% NaCl drinking water) for 2 wk induced increased serum concentration and urinary excretion of the NO decomposition products, NO2 + NO3. Urinary NO2 + NO3 and sodium excretion were significantly correlated. Compared with controls, chronically salt-loaded rats also demonstrated enhanced renal hemodynamic responses to NO synthase inhibition. We conclude that the endogenous NO system directly modulates renal hemodynamics and sodium handling and participates in the renal adaptation to increased dietary salt intake. Enhanced NO synthesis in response to increased salt intake may facilitate sodium excretion and allow maintenance of normal blood pressure.     

Rofecoxib decreases renal injury in obese Zucker rats

The present study tested the hypothesis that altered vascular regulation of arachidonic acid enzymes in obese Zucker rats contributes to renal damage. Protein expression of CYP450 (cytochrome P450) and COX (cyclo-oxygenase) enzymes in renal microvessels was studied in obese and lean Zucker rats at 20-21 weeks of age. Body weight and blood glucose averaged 649+/-13 g and 142+/-10 mg/dl in obese Zucker rats compared with 437+/-10 g and 111+/-5 mg/dl in age-matched lean Zucker rats. Renal microvascular CYP4A and COX-2 protein levels were increased and CYP2C protein levels decreased in obese Zucker rats. TX (thromboxane) B2 excretion was 2-fold higher and PG (prostaglandin) E2 excretion significantly lower in obese Zucker rats. Additional studies investigated the ability of the COX-2 inhibitor, rofecoxib, to slow the progression of renal injury in obese Zucker rats. Rofecoxib treatment decreased urinary PGF2alpha and 8-isoprostane levels in obese Zucker rats. Renal microvessel mRNA expression of pro-inflammatory chemokines was decreased in COX-2-inhibitor-treated obese Zucker rats. Urinary albumin excretion, an index of kidney damage, averaged 95+/-11 mg/day in vehicle-treated and 9+/-1 mg/day in rofecoxib-treated obese Zucker rats. Glomerulosclerosis, characterized by mesangial expansion, tubulo-interstitial fibrosis and extracellular matrix accumulation, was prominent in obese Zucker rats compared with a lack of damage in age-matched lean Zucker rats and rofecoxib-treated obese Zucker rats. These results suggest that altered vascular arachidonic acid enzymes contribute to the renal damage, and that COX-2 inhibition decreases glomerular injury in obese Zucker rats.     

Cyclooxygenase inhibitors in urinary bladder cancer: in vitro and in vivo effects

More than 14,000 people die from invasive transitional cell carcinoma (TCC) of the urinary bladder yearly in the United States. Cyclooxygenase (COX)-inhibiting drugs are emerging as potential antitumor agents in TCC. The optimal in vitro or in vivo systems to investigate COX inhibitor antitumor effects have not been defined. The purpose of this study was to determine COX-1 and COX-2 expression and antitumor effects of COX inhibitors in human TCC cell lines (HT1376, RT4, and UMUC3 cells) and xenografts derived from those cell lines. COX-2 expression (Western blot, immunocytochemistry) was high in HT1376, modest in RT4, and absent in UMUC3 cells in vitro. Similarly, COX-2 expression was noted in RT4 but not UMUC3 xenografts. COX-2 expression in HT1376 xenografts was slightly lower than that observed in vitro. None of four COX inhibitors evaluated (celecoxib, piroxicam, valeryl salicylate, and NS398) reduced TCC growth in standard in vitro proliferation assays at concentrations that could be safely achieved in vivo (< or =5 micromol/L). Higher celecoxib concentrations (> or =50 micromol/L) inhibited proliferation and induced apoptosis in all three cell lines. Celecoxib or piroxicam treatment in athymic mice significantly delayed progression of HT1376 xenografts, which express COX-2, but not UMUC3 xenografts that lack COX-2 expression. In conclusion, standard in vitro assays were not useful in predicting COX inhibitor antitumor effects observed in vivo. Athymic mice bearing TCC xenografts provide a useful in vivo system for COX inhibitor studies. Results of this study provide justification for further evaluation of COX inhibitors as antitumor agents against TCC.     

Effect of chronic and progressive hepatic outflow blockade on renal function in rats

Systemic and splanchnic hemodynamics, plasma concentration, and urinary excretion of several hormones and the changes in renal function induced by saline infusion were studied in rats with a chronic and progressive model of postsinusoidal hypertension by hepatic vein ligation (HVL) and in a control group. HVL rats showed no differences in systemic hemodynamics compared with control rats, with the exception of decreased renal blood flow and increased renal vascular resistance. HVL rats showed increased portal and intrahepatic pressure, without other differences in splanchnic hemodynamics or in portal-systemic shunts. Clearance studies revealed that under basal conditions, HVL rats showed lower glomerular filtration rate, renal plasma flow, urinary flow, and sodium, chloride, and potassium excretion than control rats. After saline infusion (3% body weight, 15 ml/hr) differences in glomerular filtration rate became nonsignificant, but urinary flow and electrolyte excretion remained lower in HVL than in control rats. Under basal conditions, plasma norepinephrine and dopamine concentrations were higher and urinary prostaglandin E2 (PGE2) and prostaglandin F2 alpha levels were lower in HVL than in control animals. These results demonstrate that chronic and progressive hepatic congestion results in impaired renal function with decreased water and electrolyte excretion, and suggest the involvement of a hepatorenal sympathetic reflex in these alterations. Renal effects could also be mediated by the low levels of PGE.     

Blockade of central cyclooxygenase (COX) pathways enhances the cannabinoid-induced antinociceptive effects on inflammatory temporomandibular joint (TMJ) nociception

The present study is the first to investigate the participation of central cyclooxygenase (COX) pathways in modulating the antinociceptive effects of intracisternally administered cannabinoid on nociception induced by inflammation of the temporomandibular joint (TMJ) in freely moving rats. Following intra-articular injection of 5% formalin in the TMJ, nociceptive scratching behavior was recorded for nine successive 5-min intervals in Sprague-Dawley rats. Intracisternal injection of 30 microg of WIN 55,212-2, a synthetic non-subtype-selective CB1/2 agonist, administered 20 min prior to formalin injection significantly reduced the number of scratches and duration of scratching induced by formalin compared with the vehicle-treated group. Antinociceptive effect of WIN 55,212-2 was blocked by intracisternal injection of 10 microg of AM251, a CB1 receptor-selective antagonist, but not by AM630, a CB2 receptor-selective antagonist. A 10 microg dose of WIN 55,212-2 that was ineffective in producing antinociception became effective following intracisternal administration of NS-398, a selective COX-2 inhibitor; indomethacin, a non-selective COX 1/2 inhibitor; acetaminophen, a putative COX-3 inhibitor, but not following pretreatment with the selective COX-1 inhibitor, SC-560. The ED(50) value of WIN 55,212-2 in the NS-398-treated group was significantly lower than that in the vehicle-treated group. Importantly, administration of low doses of COX inhibitors alone did not attenuate nociception. These results indicate that inhibition of central COX pathways, presumably via COX-2 inhibition, reduces inflammatory pain by enhancing the cannabinoid-induced antinociceptive effect. Based on our observations, combined administration of cannabinoids with COX inhibitors may hold a therapeutic promise in the treatment of inflammatory TMJ pain.     

Renal effects of antihypertensive therapy in uninephrectomized diabetic rats

Diabetic nephropathy is a major cause of chronic renal failure. The evidence available indicates that renal hemodynamics are altered in clinical and experimental diabetes mellitus. In these circumstances, an increased glomerular filtration rate (GFR) is associated with albuminuria and eventually with glomerulosclerosis. We studied the renal and hemodynamic effects of long-term treatment (5 months) using an angiotensin-converting enzyme inhibitor (trandolapril, 0.7 mg/g b.w. per day) and a calcium antagonist (verapamil, 20 mg/g b.w. per day), and the combination of the two (veratran) at the same dose, on streptozotocin-diabetic uninephrectomized rats. A moderate degree of hyperglycemia (2–4 g/l) was maintained with daily insulin. Mean arterial pressure (MAP) was measured monthly using the tail-cuff method. Determinations were made of urinary protein excretion, creatinine clearance, urinary electrolyte excretion and, at the end of treatment, renal and cardiac hypertrophy. MAP was similar in control and untreated diabetic rats. Trandolapril and veratran reduced MAP whereas verapamil alone had no effect on these animals. All groups showed a slight proteinuria that increased with verapamil treatment. The GFR of diabetic animals was higher than in the control group (mainly the first 2 months), except for veratran group, in which it was similar to the control value. Urinary electrolyte excretion increased in all diabetic groups with no significant differences among them. Veratran induced a protective effect against cardiac hypertrophy. None of the treatments affected renal hypertrophy. It is concluded that in a murine model of diabetes without hypertension or proteinuria, a combination of verapamil and trandolapril prevents hyperfiltration whereas verapamil alone increases proteinuria.     

Effects of the renal vasodilator prodrug CGP 22 979A and its parent compound CGP 18 137A on renal and central hemodynamics in conscious spontaneously hypertensive rats

In a previous study we reported that the renal prodrug CGP 22 979A (N-acetyl-L-glutamic acid-N-[N2-(5-n-butyl-2-pyridyl)-hydrazide) causes selective renal vasodilation in conscious spontaneously hypertensive rats (SHR) in doses up to 10 mg/kg. The hydralazine-like parent compound CGP 18 137A (2-hydrazino-5-n-butyl-pyridine) causes general vasodilatation. In the present study we report on renal hemodynamics, excretion of water and sodium and central hemodynamic effects of CGP 18 137A and CGP 22 979A in conscious, unrestrained SHR. CGP 18 137A (1 mg/kg) reduced effective renal plasma flow [measured as plasma clearance of [125I]p-aminohippuric acid] and glomerular filtration rate (measured as plasma-clearance of 51Cr-EDTA), in the first hour after injection. CGP 22 979A (3-30 mg/kg) dose-dependently increased effective renal plasma flow, but not glomerular filtration rate thus reducing filtration fraction. In spite of the lack of increase of glomerular filtration rate, CGP 22 979A increased excretion of sodium and water in a separate group of SHR. CGP 18 137A reduced renal excretory function slightly. In another group of conscious SHR we studied the effects of CGP 18 137A and CGP 22 979A on central hemodynamics. These animals had an electromagnetic flow-probe on the ascending aorta, to measure cardiac output (CO). Mean arterial pressure was measured from a chronic catheter in the abdominal aorta. Total peripheral resistance (TPR) and stroke volume were calculated. CGP 18 137A (0.3-1 mg/kg) reduced mean arterial pressure and TPR whereas CO increased immediately after injection.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cyclooxygenase-1 in the spinal cord plays an important role in postoperative pain

Cyclooxygenase-2 (COX-2) activity in the spinal cord plays a key role in sensitization to sensory stimuli during acute inflammation. In contrast, intrathecal administration of COX-2 specific inhibitors has minimal analgesic effects in an incisional model of postoperative pain. We investigated the role of COX isoforms in this model by examining the expression of COX-1 and the effect of intrathecal COX inhibitors. A 1cm longitudinal incision was made through skin, fascia and muscles of the plantar aspect of the left paw in male rats, and withdrawal threshold to von Frey filaments measured. Rats were perfused at 1, 2, 3, 5, and 7 days after incision, and COX-1 immunohistochemistry was performed on L3 to S2 spinal cord and gracile nucleus sections. Other rats received intrathecally the COX-1 preferring inhibitor, ketorolac, the specific COX-1 inhibitor, SC-560, the COX-2 inhibitor, NS-398 or vehicle 1 day after surgery. Withdrawal threshold was measured at intervals up to 5 days later. COX-1 immunoreactivity increased in glia in the ipsilateral L4-L6 spinal dorsal horn and ipsilateral gracile nucleus after incision. Mechanical allodynia peaked on postoperative day 1, and COX-1 immunoreactivity increased on day 1, peaked on day 2, and declined thereafter. Ketorolac and SC-560 dose-dependently increased withdrawal threshold in this model, but NS-398 had no effect. These results suggest that COX-1 plays an important role in spinal cord pain processing and sensitization after surgery. Increased COX-1 activity could precede the up-regulation of COX-1 protein, and spinally administered specific COX-1 inhibitors may be useful to treat postoperative pain.     

Phenylbutazone-induced decrease in renal blood flow

Phenylbutazone (Butazolidin), and anti-inflammatory agent, has been reported to decrease renal excretion of sodium and water. Whether or not an alteration in renal hemodynamics could be involved in producing these effects was tested in anesthetized dogs. Renal blood flow (RBF) was monitored with electromagnetic flow probes. After i.v. administration of phenylbutazone, 2 mg/kg, RBF fell by 20%. Glomerular filtration rate, sodium and water excretion were also decreased and blood pressure increased slightly. The reduction of RBF and glomerular filtration rate by phenylbutazone indicates that a hemodynamic mechanism could be involved in the retention of sodium and water induced by this agent. The decreased blood flow was correlated with a depressed renal secretion of prostaglandin E. Also, in animals pretreated with indomethacin, another inhibitor of prostaglandin synthesis, administration of phenylbutazone did not result in any additional changes in renal hemodynamics or excretion of sodium and water. In addition, phenylbutazone antagonized the ability of furosemide to increase RBF, an inhibition which has previously been shown to occur with indomethacin. Thus, phenylbutazone appears to alter renal mechanisms in a manner similar to indomethacin.     

Fenofibrate treatment of diabetic rats reduces nitrosative stress, renal cyclooxygenase-2 expression, and enhanced renal prostaglandin release

Renal cyclooxygenase (COX)-2 expression is increased in the diabetic rat and has been linked to increased glomerular filtration rate (GFR) and renal injury. Our studies indicate that oxidative stress in the form of peroxynitrite (ONOO) may be the stimulus for induction of COX-2. In this study, we addressed the effects of a peroxisome proliferator-activated receptor alpha agonist on renal COX-2 expression as fibrates exert renal protective effects. Forty-eight hours after the induction of diabetes with streptozotocin in male Wistar rats, fenofibrate treatment (100 mg/kg/day) was started, and the effects were compared with untreated diabetic rats and treated and untreated age-matched control rats (n = 5 per group). After 12 to 14 weeks of treatment, the right kidney was perfused to determine prostaglandin release in response to arachidonic acid (AA), and the left kidney was used to examine the expression of COX-2 and nitrotyrosine, an index of ONOO formation. Release of prostaglandin (PG) E(2) in response to AA was enhanced in the diabetic rat kidney compared with control (4.8 +/- 0.7 versus 1.9 +/- 0.7 ng/min) and reduced by fenofibrate to 0.6 +/- 0.2 ng/min. A similar pattern was obtained for AA-stimulated release of 6-ketoPGF(1alpha). The effects of fenofibrate were associated with reduced renal expression of COX-2 and nitrotyrosine in diabetic rats. We used creatinine clearance as an index of GFR, which was increased in the diabetic rat, 3.09 +/- 0.4 versus 1.15 +/- 0.1 ml/min for control, and reduced by fenofibrate treatment to 1.87 +/- 0.3 ml/min. These results show that fenofibrate treatment of diabetic rats decreases renal COX-2 expression, possibly by reducing nitrosative stress, and is associated with a reduction of the enhanced GFR.     

Interaction of cyclooxygenase isoenzymes, nitric oxide, and afferent neurons in gastric mucosal defense in rats

The cyclooxygenase (COX)-2 inhibitors 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5II)-furanone (DFU) (0.02-2 mg/kg) and N-[2-(cyclohexyloxy)-4-nitrofenyl]-methanesulfonamide (NS-398) (0.01-1 mg/kg), the COX-1 inhibitor 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC-560) (0.05-5 mg/kg), and dexamethasone (1 mg/kg) were studied in rats challenged with intragastric acid (300 mM HCl). All compounds induced severe gastric damage when rats were treated concurrently with the inhibitor of constitutive and inducible nitric-oxide (NO) synthase N(G)-monomethyl-L-arginine methyl ester (L-NAME) (3 or 40 mg/kg). DFU and NS-398 caused significantly less damage in rats receiving the selective inhibitor of inducible NO synthase N-(3-(aminomethyl)benzyl)acetamidine (1400W) (0.3 mg/kg). The COX-1 inhibitor SC-560 induced moderate damage in the acid-challenged stomach even without suppression of NO, but damage was aggravated by L-NAME. The COX-3 inhibitor phenacetin (400 mg/kg) did not injure the gastric mucosa despite suppression of NO. Furthermore, DFU, NS-398, SC-560, and dexamethasone caused severe injury in the acid-challenged stomach of rats pretreated with capsaicin to ablate afferent neurons. The mucosal damage induced by the COX-1 inhibitor, the COX-2 inhibitors, and dexamethasone in L-NAME- or capsaicin-treated rats was reversed by coadministration of 16,16-dimethyl-prostaglandin E2 (2 x 8 ng/kg). Gross mucosal damage was paralleled by histology. Our results support the concept that endogenous NO, prostaglandins, and afferent neurons act in concert in the regulation of gastric mucosal integrity. The prostaglandins necessary for mucosal defense in the face of NO suppression, and afferent nerve ablation can be derived either from COX-1 or COX-2. The data do not propose a protective role for a phenacetin-sensitive COX-3. Our findings suggest that not only COX-1 but also COX-2 has important functions in the maintenance of gastric integrity.     

Cyclooxygenase 2 Modulates Killing of Cytotoxic T Lymphocytes by Colon Cancer Cells

Although anti-cancer effects of cyclooxygenase 2 (COX2) inhibitors have been reported, most studies focused on the direct effects of COX2 inhibiters on colon cancer cells. On the other hand, several types of cancers express Fas ligand (FasL) and/or TRAIL and mediate apoptosis of T cells in vitro. The “counter-attack” machinery may account for the mechanisms by which tumors evade host immune surveillance. In this study we determined if COX2 inhibitor could modulate effector molecules of cell death on colon cancer cells changing their effects on cytotoxic T lymphocytes. Colon adenocarcinoma cells, HCA7 and HCT116, the former COX2-positive and the latter COX2-negative, were pre-incubated with/without a COX2 inhibitor, NS398. Subsequently, the cells were co-cultured with Jurkat T cell leukemia cells and damage to Jurkat cells was determined. Treatment with NS398 resulted in reduction of expression of FasL and TRAIL in HCA7 cells, whereas NS398 did not affect the expression of FasL and TRAIL in HCT116 cells. The number of viable Jurkat cells was diminished when cells were co-cultured with naive, non-pretreated HCA7 or HCA116 cells. Preincubation of HCA7 cells with NS398 before co-culture blunted the HCA7 cell-induced cell toxicity on Jurkat cells. In contrast, pretreatment with NS398 failed to inhibit the HCT116-induced Jurkat cell killing. Our results suggest that COX2 regulates the expression of FasL and TRAIL on COX2-positive colon cancer cells thereby evoking a counter-attack against cytotoxic T cells, which may lead to compromised host immune responses.     

罗格列酮对糖尿病大鼠肾脏病理改变的影响

目的 观察罗格列酮对糖尿病大鼠肾脏组织病理改变的影响并探讨其作用机制.方法 24只SD大鼠随机分成3组,糖尿病组:腹腔注射含链酶佐菌素(STZ)60 mg/kg;罗格列酮治疗组:先腹腔注射STZ 60 mg/kg,第4天起给予0.9%氯化钠溶液溶解的罗格列酮1 mg/(kg·d)灌胃.8周后,观察3组肾脏组织在光镜、电镜下的病理表现,用免疫组化法和逆转录-聚合酶链式反应法观察环氧化酶-2(COX-2)的蛋白表达和COX-2mRNA的表达.结果 正常对照组大鼠肾脏无明显病理变化.糖尿病组大鼠肾脏在光镜下显示肾小球细胞外基质增多,基底膜增厚,肾小管有炎症细胞浸润;在电镜下显示肾小球细胞基底膜不均匀,相邻足突大部分融合或缺失.罗格列酮治疗组病理改变较糖尿病组减轻.糖尿病组大鼠COX-2蛋白表达较正常对照组明显上调,罗格列酮组较糖尿病组明显下调.糖尿病组大鼠COX-2mRNA(0.474±0.012)在肾脏的表达较正常对照组(0.342±0.016)显著上调(P＜0.01),罗格列酮组(0.369±0.025)较糖尿病组显著下调(P＜0.01).结论 STZ诱导的糖尿病大鼠的肾脏具有COX-2介导的病理改变,罗格列酮可以抑制COX-2的表达,改善糖尿病大鼠肾脏的病理改变.     

Effects of cyclooxygenase-2 (COX-2) inhibition on plasma and renal renin in diabetes

COX-2-derived prostaglandins (PG) have been suggested to be important modulators of renin release and expression. However, the role of COX-2 in various high-renin states is still being debated. In the present studies we explored the role of COX-2-derived PG on basal and angiotensin converting enzyme inhibitor (ACEI)-stimulated plasma and renal renin concentrations (PRC and RRC, RIA), and mRNA expression (RmRNA, RNAse protection assay) in experimental diabetes (DM). Groups of moderately hyperglycemic (n = 5, approximately 350 mg/dl), streptozotocin-diabetic rats (D) after 3 weeks of DM were treated with a selective COX-2 inhibitor, MF-tricyclic (MF, 5 mg/kg/day for 10 days in food), the combination of MF and the ACEI enalapril (3 mg/kg/day), enalapril alone, or vehicle (MF-free chow), for 10 days. Non-diabetic control rats, fed MF-free chow, were also studied. All groups of diabetic rats demonstrated similar glycemic control. Treatment with ACEI resulted in significant elevations in PRC, RRC and RmRNA as compared to non-ACEI treated groups of diabetic and control rats. A similar rise in these parameters was observed in the rats treated with the combination of ACEI and MF. Furthermore, in diabetic rats treated with MF alone, PRC and RRC were similar to vehicle-treated animals. Diabetic rats demonstrated higher urinary PG as compared to controls. MF-treated rats demonstrated a significant reduction in urinary PG excretion. In summary, selective COX-2 inhibition influenced neither basal renin status nor ACEI-induced renin release and expression in diabetic rats. These findings do not support a significant role for COX-2 in mediating renin status in diabetes.     

A(1) receptor blockade induces natriuresis with a favorable renal hemodynamic profile in SHHF/Mcc-fa(cp) rats chronically treated with salt and furosemide.

Our goal was to test the hypothesis that A(1) receptor blockade induces diuresis/natriuresis with a favorable renal hemodynamic/cardiac profile in aged, lean SHHF/Mcc-fa(cp) rats, a rodent model of hypertensive dilated cardiomyopathy. Thirteen-month-old SHHF/Mcc-fa(cp) rats were pretreated for 72 h before experiments with furosemide (100 mg/kg by gavage 72, 48, and 24 h before experiments) to mimic the clinical setting of chronic diuretic therapy and were given 1% NaCl as drinking water to reduce dehydration/sodium depletion. Animals were instrumented for measurement of systemic and renal hemodynamics, renal excretory function, and cardiac performance, and baseline values were obtained during a 30-min clearance period. Animals then received either vehicle (n = 9), BG9719 [the S-enantiomer of 1,3-dipropyl-8-[2-(5,6-epoxynorbornyl)] xanthine (also called CVT-124)] (highly selective A(1) receptor antagonist; 0.1 mg/kg bolus + 10 microg/kg/min; n = 9) or furosemide (loop diuretic; 30 mg/kg; n = 8) and measurements were repeated during four subsequent clearance periods. Both BG9719 and furosemide increased urine volume and absolute and fractional sodium excretion. BG9719 increased renal blood flow and glomerular filtration rate, but did not affect fractional potassium excretion. Furosemide decreased renal blood flow and glomerular filtration rate and increased fractional potassium excretion. Neither drug altered afterload; however, furosemide, but not BG9719, decreased preload (central venous pressure and ventricular end diastolic pressure). Neither drug altered systolic function (+dP/dt(max)); however, furosemide, but not BG9719, attenuated diastolic function (decreased -dP/dt(max), increased tau). In the setting of left ventricular dysfunction, chronic salt loading and prior loop diuretic treatment, selective A(1) receptor antagonists are effective diuretic/natriuretic agents with a favorable renal hemodynamic/cardiac performance profile.     

Inhibition of cyclooxygenase-2 decreases DNA synthesis induced by platelet-derived growth factor in Swiss 3T3 fibroblasts

NS-398 [N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide], a selective inhibitor of cyclooxygenase-2 (COX-2), inhibited proliferation induced by platelet-derived growth factor (PDGF) in Swiss 3T3 fibroblasts. The effect of NS-398 was found to be concentration-dependent. The half-maximal effect occurred at approximately 0.1 microM. NS-398 decreased mitogenesis at subsaturating PDGF concentrations and the inhibitory effect of NS-398 was overcome by increasing PDGF concentration. SC-236, another COX-2 selective inhibitor, also inhibited PDGF-induced proliferation. In contrast, two selective COX-1 inhibitors, valeryl salicylate and ketorolac, had no significant inhibitory effect on PDGF-stimulated DNA synthesis. The inhibition was obtained when NS-398 was added during the first hour after PDGF addition. At 1 h, PDGF induced COX-2 protein and prostaglandin (PG)E(2) synthesis, and NS-398 blocked the synthesis of PGE(2). The inhibitory effect of NS-398 on PDGF-stimulated DNA synthesis was counteracted by 280 nM PGE(2). The antimitogenic action of NS-398 and SC-236 suggests that selective inhibition of COX-2 may produce antiproliferative effects with substantial safety advantages over nonselective COX inhibitors.     

Role of Hemodynamic Changes in the Increased Cation Excretion after Acute Unilateral Nephrectomy in the Anesthetized Dog

Studies were carried out in anesthetized dogs to characterize the increase in cation excretion which occurs after acute unilateral nephrectomy (AUN). 60 min after AUN, cation excretion had increased from 31.5+/-2.7 to 66.3+/-12.0 mueq/min (P < 0.005) and fractional cation excretion had increased from 0.56+/-0.05 to 1.03+/-0.14% (P < 0.005), as the glomerular filtration rate was unchanged and renal blood flow fell. The increased cation excretion was accompanied by an increase in fractional phosphate excretion, no change in chloride excretion, and a fall in renin secretion. These alterations in renal function were associated with marked changes in systemic hemodynamics: cardiac output fell from 2.52+/-0.24 to 1.85+/-0.16 liters/min (P < 0.001), as diastolic pressure rose without an overall increase in mean arterial pressure, and heart rate fell.To assess the importance of these hemodynamic changes in the renal response, AUN in a separate group of dogs was accompanied by the simultaneous opening of a surgically created femoral artery-to-vein fistula at flow matching the blood flow to the removed kidney. When this was done, no alterations in systemic or renal hemodynamics were observed, and cation excretion did not differ from control. Subsequent closure of the fistula then caused a fall in cardiac output from 2.15+/-0.25 to 1.77+/-0.20 liters/min (P < 0.05), and an increase in cation excretion from 34.6+/-9.5 to 52.3+/-13.7 mueq/min (P < 0.01), thus mimicking the findings with AUN alone.These results demonstrate that AUN causes hemodynamic changes resembling those seen on closure of a chronic arteriovenous fistula. Prevention of these hemodynamic changes after AUN also prevents the functional adjustment of the remaining kidney, suggesting that they may be important in initiating the renal response. The increased electrolyte excretion after AUN may occur through mechanisms similar to that seen on closure of an arteriovenous fistula.