Metalloproteinase activity is present in rat urine and derived from the renal cortex

Summary: Matrix metalloproteinases (MP) are important candidates for the degradation of extracellular matrix, but the role of MP in the diseased kidney remains poorly understood. to examine the significance of urinary MP, we first investigated the characteristics of MP in normal rat urine and renal cortex, and then evaluated the urinary MP activity in anti-thymocyte induced glomerulonephritis (Thy.1 GN). Metalloproteinase activity was measured as the EDTA-inhibitable degradation of [³H] gelatin. the enzyme was purified from urine and the renal cortex homogenate in normal Wistar rats by using several chromatographic and gel filtration methods. Both materials contained the identical molecular weight (Mr 126 kDa by gel permeation method) of gelatin-degrading enzymes, the activity of which was inhibited by metal chelating agents and reactivated by ZnC1₂ but not by other proteinase inhibitors. Thy.1 GN was induced by intravenous injection of rabbit anti-thymocyte serum into rats, and daily urine was collected at sequential time points. Urinary MP activity was markedly reduced soon after the serum injection, and returned to the control level in 9 weeks. Conversely, urinary MP-inhibitor activity (Mr 30 kDa), determined as inhibiting activity against MP derived from renal cortex, showed serial changes strikingly reflected as urinary MP activity. These findings suggested that rat urine contained the MP which seemed to be derived from the renal cortex, and the urinary MP activity was decreased in Thy.1 GN model, probably due to the presence of MP-inhibitor. As urinary MP is likely to reflect intra-renal MP, the evaluation of urinary MP may be useful to search metabolic alteration of extracellular matrix in the diseased kidney.     

Chronic salt loading upregulates expression of adrenomedullin and its receptors in adrenal glands and kidneys of the rat

The vasodilator peptide adrenomedullin (AM) elicits diuresis and natriuresis and inhibits aldosterone secretion. The aim of this study was to better understand the role of AM in maintaining water and electrolyte balance during chronic salt loading. Male Wistar rats were divided into a high salt (HS) group that received a diet containing 8% sodium chloride (NaCl) and a normal salt group that received a diet containing 0.4% NaCl. Plasma AM concentrations as well as expression of AM mRNA in the adrenal gland and kidney were then measured after 3, 7, 14, and 28 days. After 28 days, sodium and water excretion were significantly higher in HS rats than in control, although blood pressure and fluid volume were not significantly affected. Moreover, although plasma AM remained unchanged for up to 14 days, it was increased 2.5-fold in HS rats after 28 days on a high salt diet, and there were corresponding 3-fold and 1.5-fold increases in the levels of AM mRNA in the adrenal gland and kidney, respectively. At the same time, expression of calcitonin receptor-like receptor mRNA was significantly upregulated in both kidney and adrenal gland, as was expression of receptor activity-modify protein 1 (RAMP1) and RAMP2 mRNA in the adrenals and expression of RAMP3 in kidneys. Taken together, these results suggest that AM plays a role in the regulation of water and electrolyte balance in animals chronically ingesting high levels of salt.     

Protein-losing gastropathy associated with autoimmune disease: successful treatment with prednisolone

99m Tc-labeled human serum albumin scintigram showing abnormal radioactivity in the stomach. Endoscopic gastric biopsies revealed nonspecific inflammation, but marked intramural edema. Based on a slight elevation of antinuclear antibody level, autoimmune disease was suspected to be involved in this patient. Administration of prednisolone, as a diagnostic therapy, alleviated the hypoproteinemia, hypoalbuminemia, and hypercholesteremia. These findings suggest that an autoimmune mechanism could have been involved in this case of protein-losing gastropathy. Received: September 4, 2000 / Accepted: February 23, 2001     

Increased plasma and joint tissue adrenomedullin concentrations in patients with rheumatoid arthritis compared to those with osteoarthritis

OBJECTIVE: To elucidate the pathophysiological role of adrenomedullin (AM) in rheumatoid arthritis (RA), plasma AM concentration was measured in patients with RA and in healthy contols. The concentration of AM in joint fluid, synovial tissue, and articular cartilage of patients with RA and osteoarthritis (OA) were measured and compared. METHODS: Twenty-six patients with RA (aged 62 +/- 4 yrs, all female), 10 healthy controls (aged 57 +/- 5 yrs, all female), and 10 patients with OA (aged 68 +/- 8 yrs, all female) were studied. We measured plasma levels of total and mature AM by immunoradiometric assay and levels of AM in joint tissue by radioimmunoassay. RESULTS: Plasma levels of AM in patients with RA (18.35 +/- 6.9 fmol/ml) were found to exceed those in healthy controls (11.64 +/- 2.8 fmol/ml). Moreover, plasma AM showed a significant positive correlation with plasma C-reactive protein (CRP). The correlation coefficient of total AM was 0.685, and that of mature AM was 0.624. Similarly, AM levels in synovium and joint fluid in patients with RA were significantly higher than in OA. In contrast, AM levels in articular cartilage were found to be low, with no significant difference in levels between patients with RA and OA. CONCLUSION: The relation between plasma AM levels and plasma CRP in patients with RA suggests that plasma AM levels increase with the activity of RA. Moreover, AM levels in synovium and joint fluid of patients with RA were significantly higher than those of patients with OA. Thus, AM probably plays a part in the regulation of the inflammatory process of RA.     

Relationship between serum IgA/C3 ratio and progression of IgA nephropathy

OBJECTIVE: The serum IgA/C3 ratio might be considered to serve as a diagnostic marker for patients with IgA nephropathy (IgAN), but its value as a marker of the severity of histological lesions or prognosis is unknown. METHODS: We studied the serum IgA/C3 ratio, using standardized reference material, in 86 patients with IgAN and in 32 with non-IgAN. The patients with IgAN were divided according to the severity of histological lesions (mild IgAN, n=29 and severe IgAN, n=57) based on Japanese clinical guidelines. RESULTS: The serum IgA level was significantly higher, while its C3 level was lower in patients with severe IgAN compared to those with non-IgAN. However, these levels were not different between patients with mild IgAN and non-IgAN. In contrast, the serum IgA/C3 ratio obviously differed among the three groups (2.47+/-0.96 vs. 3.63+/-1.44 vs. 4.72+/-1.86; p<0.01, ANOVA). Kaplan-Meier analysis of the patients with IgAN classified according to the mean serum IgA/C3 ratio revealed that the group with high serum IgA/C3 (4.5 and above) had a significantly poorer renal outcome (p<0.05, log-rank test), since the cumulative renal survival rate at 5 years was 84.4% vs. 100%. The ratio (%) of patients with severe IgAN in whom hematuria disappeared, was significantly higher in the low, than in the high serum IgA/C3 group (41.9% vs. 15.4%; p<0.05, t-test). CONCLUSION: The serum IgA/C3 ratio appears to reflect the histological severity of IgAN and could serve as a marker of the progression of IgAN.     

Antifibrotic effect of adrenomedullin on coronary adventitia in angiotensin II-induced hypertensive rats

OBJECTIVE: The extracellular matrix (ECM) determines the structural integrity of the heart and vasculature, participating in cardiovascular remodeling. We previously reported that adrenomedullin (AM) inhibited cellular proliferation and protein synthesis of cardiac fibroblasts; however, the precise mechanisms of AM actions as an antifibrotic factor remain unknown. The purpose of this study was to examine the biological actions of AM against the profibrotic factor angiotensin II (Ang II) in coronary adventitia. METHODS AND RESULTS: Rats with hypertension induced by Ang II infusion were administered 0.06 mug/kg/min recombinant human AM subcutaneously for 14 days. The AM infusion significantly (p<0.05) reduced the Ang II-induced increase of coronary adventitial fibroblasts expressing Ki-67 and alpha-smooth muscle actin (alpha-SMA) in the left ventricle, by 65%, and 62%, respectively, without affecting systolic blood pressure, left ventricle/body weight, or cross-sectional area of myocardial fibers. Collagen deposition of coronary arteries was reduced by the AM infusion (-24%, p<0.01), and these effects of AM were accompanied by significant reductions in gene expression of type 1 collagen (-49%, p<0.05) and transforming growth factor-beta1 (TGF-beta1) (-55%, p<0.01). In cultured cardiac fibroblasts, 10(-7) mol/L AM exerted an inhibitory effect on TGF-beta1-induced alpha-SMA expression (p<0.01) that was mimicked by 8-bromo-cAMP and attenuated by the protein kinase A inhibitor H-89. CONCLUSION: AM decreased Ang II-induced collagen deposition surrounding the coronary arteries, inhibiting myofibroblast differentiation and expressions of ECM-related genes in rats. The present findings further support the biological action of AM as an antifibrotic factor in vascular remodeling.     

Two cases of interstitial nephritis with primary Sjögren's syndrome successfully treated by steroid therapy

We have experienced two cases of interstitial nephritis with Sj?gren's syndrome successfully treated by steroid therapy. Case 1. A 50-year-old woman was admitted because of rash and arthralgia of the limb. Although her renal function was normal, serum IgG was extremely high and gallium-67 scintigrams indicated abnormal uptake in both kidneys with swelling on CT scans. Renal biopsy specimens showed a patchy dense interstitial infiltration of lymphocytes, monocytes and partly plasma cells with tubular cell atrophy. To suppress an excessive immune reaction, oral prednisolone was administrated at a dose of 30 mg/day. Six weeks after inception of the therapy, re-biopsy specimens showed a decrease in interstitial infiltration, particularly plasma cells, and interstitial fibrosis did not progress. After 8 weeks, the serum IgG level was normalized. Case 2. A 57-year-old woman was found to have renal involvement(serum creatinine level: 2.2 mg/dl) and anemia. Clinical findings suggested primary Sj?gren's syndrome with renal tubular acidosis. Renal biopsy specimens showed a moderate to severe interstitial infiltration of inflammatory cells. After inception of steroid therapy(prednisolone 40 mg/day), renal involvement and renal anemia gradually improved. The renal function has been kept stable(serum creatinine level: 1.5 mg/dl) for 9 years by low-dose steroid therapy. These two cases suggest that steroid therapy plays two important roles: controlling of the acute immune reaction that causes renal fibrosis to progress in case 1, and long-term preservation of the renal function by the continuous use of low-doses in case 2.     

Differential blood pressure reductions by angiotensin receptor blocker plus calcium channel blocker or diuretic in elderly hypertension with or without obesity

We conducted the Miyazaki Olmesartan Therapy for Hypertension in the EldeRly (MOTHER) study, which suggested that there are preferable effects of an angiotensin receptor blocker (ARB), olmesartan, plus a calcium channel blocker (CCB) over the ARB plus a diuretic, in elderly patients with hypertension. In this subanalysis, we examined whether obesity influences the efficacies of these combination therapies. The study subjects were 58 hypertensive patients ages 65 to 85, who had been randomly assigned to either group treated with olmesartan plus a CCB or a diuretic and completed the treatment for 6 months. Systolic and diastolic blood pressures were reduced following these combination treatments in nonobese and obese patients. In the CCB combination, blood pressure reductions in nonobese patients were larger than in obese patients at 1 and 3 months, and serum creatinine remained unchanged despite the greater reduction of blood pressure. Meanwhile, such differences were not noted in the diuretic groups. Plasma aldosterone was significantly reduced in nonobese patients of two combination groups, but not in those with obesity. ARB plus CCB combination therapy might be preferably chosen for nonobese elderly patients, whereas the influence of obesity seems smaller in the efficacy of ARB plus a diuretic.