Transport properties of nonsteroidal anti-inflammatory drugs by organic anion transporter 1 expressed in Xenopus laevis oocytes

Organic anion transporter 1 (OAT1) is the para-aminohippurate (PAH) transporter in the basolateral membrane of the proximal tubule. The present study investigated whether or not nonsteroidal anti-inflammatory drugs (NSAIDs) are transported by OAT1. All of the NSAIDs tested inhibited [14C]PAH uptake via OAT1 expressed in Xenopus laevis oocytes. Ibuprofen, indomethacin, salicylurate, and naproxen showed the strongest potency to inhibit [14C]PAH uptake (Ki approximately 2-10 microM); acetylsalicylate, salicylate, and phenacetin exhibited moderate potency (Ki approximately 300-400 microM), and acetaminophen (paracetamol) exhibited the weakest inhibitory potency (Ki approximately 2 mM). Radiolabeled acetylsalicylate, salicylate, and indomethacin were taken up by OAT1 and the uptake rate of these three NSAIDs was enhanced by the outwardly directed dicarboxylate gradient. The efflux of the preloaded [14C]PAH from the oocytes via OAT1 was trans-stimulated by PAH and glutarate added to the media. The addition of salicylate, acetylsalicylate, or salicylurate into the media also trans-stimulated the efflux of PAH, whereas indomethacin did not. The present study indicates that OAT1 is responsible for the renal uptake and secretion of NSAIDs.     

Dichapetalin-type triterpenoids and lignans from the aerial parts of Phyllanthus acutissima

Chemical investigation of the aerial parts of Phyllanthus acutissima resulted in the isolation of five new dichapetalin-type triterpenoids, acutissimatriterpenes A-E ( 1- 5), and two new lignans, acutissimalignans A ( 6) and B ( 7), along with two known lignans and three known ellagic acid derivatives. The structures of 1- 7 were determined mainly on the basis of spectroscopic methods. The compounds obtained were evaluated for cytotoxic and anti-HIV-1 activities.     

Corymine potentiates NMDA-induced currents in Xenopus oocytes expressing NR1a/NR2B glutamate receptors

Previous studies demonstrated that corymine, an indole alkaloid isolated from the leaves of Hunter zeylanica, dose-dependently inhibited strychnine-sensitive glycine-induced currents. However, it is unclear whether this alkaloid can modulate the function of the N-methyl-D-aspartate (NMDA) receptor on which glycine acts as a co-agonist via strychnine-insensitive glycine binding sites. This study aimed to evaluate the effects of corymine on NR1a/NR2B NMDA receptors expressed in Xenopus oocytes using the two-electrode voltage clamp technique. Corymine significantly potentitated the NMDA-induced currents recorded from oocytes on days 3 and 4 after cRNA injection but it showed no effect when the current was recorded on days 5 and 6. The potentiating effect of corymine on NMDA-induced currents was induced in the presence of a low concentration of glycine (< or =0.1 microM). Spermine significantly enhanced the potentiating effect of corymine observed in the oocytes on days 3 and 4, while the NMDA-receptor antagonist 2-amino-5-phosphonopentanone (AP5) and the NMDA-channel blocker 5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) reversed the effect of corymine. On the other hand, the nonspecific chloride channel blocker 4,4-di-isothiocyano stilbene-2,2-disulfonoc acid (DIDS) had no effect on the corymine potentiation of NMDA currents. There was no good correlation between corymine- and spermine-induced potentiation of the NMDA-current response in Xenopus oocytes. These results suggest that corymine potentiates the NMDA-induced currents by interacting with a site different from the spermine binding site.     

The interaction and transport of beta-lactam antibiotics with the cloned rat renal organic anion transporter 1.

In the present study, we investigated the interactions between antibiotics, especially beta-lactam antibiotics, and rat renal organic anion transporter 1 (OAT1). [(14)C]p-Aminohippurate (PAH) uptake via OAT1 expressed in Xenopus laevis oocytes was inhibited by all of the penicillins and cephalosporins tested. Penicillin G, carbenicillin, cephaloridine, cephalothin, cefazolin, and cephalexin inhibited [(14)C]PAH uptake via OAT1 in a competitive manner (K(i) = 0.29-2.33 mM). Cinoxacin, a quinolone gyrase inhibitor, also inhibited PAH uptake via OAT1. Other antibiotics, such as gentamicin, streptomycin, and vancomycin, which do not contain anionic moieties, did not interact with OAT1. [(3)H]Penicillin G and [(14)C]cephaloridine were demonstrated to be transported via OAT1. Using the cells that stably expressed OAT1, we analyzed the cytotoxicity of several beta-lactam antibiotics. Cells expressing OAT1 showed higher susceptibility to cephaloridine (a potentially nephrotoxic beta-lactam antibiotic) toxicity than did control cells. The present study suggests that OAT1 is the major organic anion transporter in the kidney that is responsible for the renal secretion of antibiotics, especially that of beta-lactam antibiotics. Furthermore, the culture cell system expressing OAT1 was revealed to be useful for the prediction of the nephrotoxicity of beta-lactam antibiotics.     

Renal blood flow after bilateral ureteral ligation in the rat

Renal blood flow (RBF) in rat was measured by using a noncannulating electromagnetic flowmeter. In the sham control rats, anesthetized with Inactin, RBF averaged 7 ml/min/g KW when arterial blood pressure was above 110 mm Hg. Auroregulation of RBF was observed when the arterial blood pressure was in the range of 110–150 mm Hg. Glomerular filtration rate (GFR), measured by polyfructosan clearance, averaged 1.08 ml/min/g KW. In experimental rats with 24 h of bilateral ureteral ligation (BUL), RBF averaged 38% of control value. During 1/2–3 h following release of the left ureteral occlusion, RBF increased to 60% of control value. The autoregulatory ability of the damaged kidney was reduced during BUL and did not improve after releasing occlusion. During the post-obstructive period arterial blood pressure remained stable. Thus, a high total renal vascular resistance was responsible for the depressed RBF. GFR in these rats averaged only 9% of control value. The reduction in RBF alone does not explain the drastic reduction in GFR in this model of renal failure.     

Cytotoxic styryl-lactones from the leaves and twigs of Polyalthia crassa

Four new styryl-lactones, crassalactones A-D (1-4), were isolated from a cytotoxic ethyl acetate-soluble extract of the leaves and twigs of Polyalthia crassa, together with seven known compounds, (+)-3-acetylaltholactone, (+)-altholactone, aristolactam AII, cinnamic acid, (+)-goniofufurone, (+)-goniopypyrone, and (+)-howiinol A. Their structures were determined on the basis of spectroscopic methods. The absolute configuration of 1-3 was established by chemical conversions. Single-crystal X-ray analysis and the Mosher ester method were used to confirm the absolute stereochemistry of 4. Cytotoxic evaluation against several mammalian cancer cell lines was performed on all new isolates, aristolactam AII, and the modified (+)-tricinnamate derivative 11 obtained from 1.     

Kidney pressures after temporary renal artery occlusion in the rat.

Acute kidney failure was produced in the anesthetized rat by 1 h of complete renal artery occlusion. Kidney function was studied either immediately after release of the occlusion or 1 day later using clearance, micropuncture, histological, and nephron dissection techniques. Polyfructosan clearance was decreased to 5% of normal after temporary occlusion. Proximal tubular pressure (PTP) averaged 13-14 mmHg in normal kidneys, 39 mmHg immediately after release of unilateral occlusion, 19 mmHg 1 day after unilateral occlusion, and 25 mmHg 1 day after bilateral occlusion. The increased PTP reduces the glomerular filtration rate (GFR). Glomerular capillary pressure, estimated from the sum of the stop-flow and arterial plasma colloid osmotic pressures, was not decreased after temporary ischemia. Single-nephron GFR, measured without intratubular pressure control, was only slightly below normal 1 day after bilateral occlusion. Most distal tubules from ischemia-damaged kidneys contained hyaline casts. Tubular obstruction is a major factor in this model of acute kidney failure.     

Suppression by Curcuma comosa Roxb. of pro-inflammatory cytokine secretion in phorbol-12-myristate-13-acetate stimulated human mononuclear cells

Curcuma comosa Roxb. is a medicinal plant that has traditionally been used in Thailand for treatment of inflammation in postpartum uterine bleeding. The purpose of this study was to evaluate its anti-inflammatory effects using peripheral blood mononuclear cells (PBMC) and human pro-monocytic cell line (U937). Pretreatment with hexane or ethanol extract or two diarylhepatanoids (5-hydroxy-7-(4-hydroxyphenyl)-1-phenyl-(1E)-1-heptene and 7-(3,4-dihydroxyphenyl)-5-hydroxy-1-phenyl-(1E)-1-heptene) of C. comosa significantly decreased the release of pro-inflammatory cytokines, tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta, from phorbol-12-myristate-13-acetate (PMA)-stimulated PBMC and U937 cells. In PMA-stimulated U937 cells, the two C. comosa diarylhepatanoids reduced the expression of TNF-alpha and suppressed expression of IkappaB kinase and activation of nuclear factor kappa B. These results indicated that C. comosa and its diarylheptanoids have anti-inflammatory properties which could be exploited for clinical use.     

2-substituted furans from Polyalthia suberosa

Two new 2-substituted furans, 1-(2-furyl)pentacosa-16,18-diyne and 23-(2-furyl)tricosa-5,7-diynoic acid, have been isolated from stems of Polyalthia suberosa. The structures were assigned by spectroscopic methods. The two compounds together with the previously reported kalasinamide, N-trans-feruloyltyramine and N-trans-coumaroyltyramine showed anti-HIV activities.     

Cytotoxic coumarins from Mammea harmandii

Two new naturally occurring coumarins, isomesuol (1) and mammearin A (2), together with nine known Mammea coumarins 3-11 were isolated from the EtOAc extract of the leaves and twigs of Mammea harmandii. Coumarins 1, 3 and 4 showed cytotoxicity against a panel of mammalian cancer cell lines. Their structures were determined by spectroscopic methods. The assignments of 13C-NMR signals of isomesuol (1), which was isolated for the first time as a natural product, have been revised.