ELMO1 increases expression of extracellular matrix proteins and inhibits cell adhesion to ECMs.

We have previously identified the engulfment and cell motility 1 (ELMO1) as a susceptibility gene for diabetic nephropathy. To elucidate the role of ELMO1 in the pathogenesis of chronic renal injury, we examined the expression of Elmo1 in the kidney of a rat model for chronic glomerulonephritis (uninephrectomy plus anti-Thy1.1 antibody [E30] injection). We found that the expression of the Elmo1 was significantly increased in the renal cortex and glomeruli of uninephrectomized rats injected with E30 compared to controls. By in situ hybridization, the expression of Elmo1 was shown to be elevated in the diseased kidney, especially in glomerular epithelial cells. In COS cells, the overexpression of ELMO1 resulted in a substantial increase in fibronectin expression, whereas the depletion of the ELMO1 by small interfering RNA (siRNA) targeting ELMO1 significantly suppressed the fibronectin expression in ELMO1 overexpressing and control cells. We also found that the expression of integrin-linked kinase (ILK) was significantly increased in ELMO1 overexpressing cells, and the ELMO1-induced increase in fibronectin was partially, but significantly, inhibited by siRNA targeting ILK. Furthermore, we identified that the cell adhesion to ECMs was considerably inhibited in cells overexpressing ELMO1. These results suggest that the ELMO1 contributes to the development and progression of chronic glomerular injury through the dysregulation of ECM metabolism and the reduction in cell adhesive properties to ECMs.

Dual effects of lisinopril on puromycin aminonucleoside nephrosis in unilaterally nephrectomized rats.

The therapeutic effects of angiotensin converting enzyme inhibitor, lisinopril, on puromycin aminonucleoside (PAN)-induced nephrosis were investigated using unilaterally nephrectomized rats. Lisinopril showed potent dual effects on PAN nephrosis. Lisinopril treatment (50 mg/l in drinking water) from day 5 or day 9 reduced urinary protein excretion and suppressed the development of glomerular sclerosis at 8 weeks after PAN injection (150 mg/kg, i.p.), indicating a therapeutic effect on the nephrosis. Recovery of decreased anionic charge sites on the glomerular basement membrane was involved, at least in part, in the therapeutic action of lisinopril against proteinuria. On the other hand, oliguria and progressive azotemia derived from continuous deterioration of the renal function was induced if the treatment of lisinopril was started on the same day as PAN injection. The renal dysfunction induced by simultaneous administration of lisinopril with PAN could be abolished by combination dosing with sarcosine, an angiotensin II (AII)-receptor agonist. These results indicate that lisinopril treatment attenuates proteinuria by ameliorating the anionic charge barrier on the glomerular basement membrane and that it also protects against the development of chronic renal disease with segmental glomerular sclerosis, although AII depletion during the acute nephrotic stage exacerbates the renal damage in PAN nephrosis of unilaterally nephrectomized rats.

Circadian rhythm of plasma uric acid and handling stress-induced hyperuricemia in conscious cebus monkeys.

An apparent circadian rhythm of plasma uric acid and the effect of handling stress on plasma uric acid level in conscious cebus monkeys were demonstrated. The lowest level of plasma uric acid in the circadian rhythm occurred early in the morning and the highest, before bedtime at night. With experimental handling stress, the plasma uric acid level rose to much more than the maximum level of the circadian rhythm. Stress-induced hyperuricemia could be inhibited without an increase of urinary uric acid excretion by the minor tranquilizer diazepam at doses of more than 1 mg/kg, p.o. On the other hand, benzbromarone at 20 mg/kg, p.o. significantly inhibited the hyperuricemia with a hyperuricosuric effect, while probenecid at 50 mg/kg, p.o. had no effect on either the increased plasma uric acid or urinary uric acid excretion. Accordingly, it is concluded that the plasma uric acid level in conscious cebus monkeys easily fluctuates with experimental conditions and that the animals can be utilized to evaluate the hypouricemic and hyperuricosuric property of benzbromarone-like agents.

Hyperuricemia induced by the uricosuric drug probenecid in rats.

Stimulation of uric acid production by the well-known uricosuric drug probenecid was studied using potassium oxonate-treated rats and eviscerated rats subjected to functional hepatectomy. In oxonate-treated rats, probenecid was hyperuricosuric, increasing the glomerular-filtered amounts of uric acid and causing marked hyperuricemia. This could be completely blocked by combination dosing with allopurinol, an inhibitor of xanthine oxidase. In eviscerated rats subjected to functional hepatectomy, probenecid also increased plasma uric acid and urinary uric acid excretion, but when given together with allopurinol, the increase of plasma uric acid was abolished with a remarkable increase of plasma hypoxanthine and xanthine. When probenecid was given by combination dosing with propranolol, a beta adrenoceptor antagonist, the hyperuricemia was also completely blocked. Thus, probenecid is concluded to stimulate uric acid production, probably via some interaction with endogenous catecholamine, resulting in hyperuricemia in rats, although it is a practical hypouricemic drug in humans.

Stop-flow studies on tubular transport of uric acid in rats.

A stop-flow technique using pyrazinoic acid(PZO)-treated and -untreated rats was devised to evaluate drug effects on bi-directional transport of uric acid in the tubules. Constant venous infusion of test drugs to PZO-untreated rats was used to estimate their inhibitory effects on urate secretion, while their inhibitory effects on urate reabsorption was studied by intravenous administration as a bolus to PZO-treated rats. Probenecid, tienilic acid and R-(+)-enantiomer of S-8666, which is the uricosuric component of a new uricosuric diuretic, decreased the (Tua/Pua)/(Tin/Pin) value in the distal and proximal tubules by inhibiting urate secretion in PZO-untreated rats. On the other hand, all of these drugs increased the (Tua/Pua)/(Tin/Pin) value in the tubules in PZO-treated rats, which suggested that they also inhibited the reabsorptive flux of urate. This stop-flow technique in rat kidneys showed the possibilities of bi-directional inhibition by these drugs of urate transport in the tubules.

Effect of 711389-S, a new antiarrhythmic agent, on myocardial energy metabolism in guinea-pigs and rats.

The effect of 711389-S, a new antiarrhythmic agent, on myocardial energy metabolism was investigated using anaesthetized guinea-pigs and rats. 711389-S elevated the adenylate energy charge and phosphorylation potential in normal guinea-pig myocardium. Large doses also increased the myocardial lactate content with ECG abnormalities. The close relationship between rate-pressure product and the myocardial energy state under 711389-S treatments showed the suppression of energy consumption due to a decrease of work output. In guinea-pigs with arrhythmic myocardia induced by intravenous infusion of ouabain, 711389-S prevented the loss of high-energy phosphate compounds and the acceleration of anaerobic glycolysis concomitant with the effective antiarrhythmic property. In ischaemic myocardium produced by ligation of the coronary artery in rats, 711389-S suppressed the decreases of creatine phosphate, NAD+ and adenylate energy charge. Moreover, this agent effectively blocked the incidence of ventricular arrhythmias at an early stage following the ligation. In all of these actions, 711389-S was more effective than disopyramide, which is in the same class of antiarrhythmics. 711389-S was concluded to be a favourable antiarrhythmic agent offering beneficial action against arrhythmic and ischaemic metabolic changes in the myocardium.

A new uricosuric diuretic, S-8666, in rats and chimpanzees.

5-Dimethylsulfamoyl-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxyli c acid (S-8666) was studied as a possible new uricosuric diuretic agent using rats and chimpanzees. Various new compounds belonging to the 5-sulfamoyl-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxylic acids were clearly diuretic with uricosuric activity in intraperitoneally oxonate-treated rats. S-8666 was chosen as a favorable candidate because its uricosuric activity due to the effects of tubular transport of uric acid were apparently more marked than those of known uricosuric agents such as probenecid, benzbromarone, tienilic acid and indacrinone in oxonate-treated rats. S-8666 was also uricosuric in rats not given urate oxidase inhibitor. The diuretic effect of S-8666 in oxonate-treated rats was as high-ceilinged as that of furosemide, while those of tienilic acid, indacrinone and a known compound of a 5-carbonyl-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxylic acid were rather low-ceilinged. These uricosuric and diuretic activities of S-8666 were manifested by two enantiomers, of which the (+)-enantiomer displayed predominantly uricosuric activity and the (-)-enantiomer, diuretic activity like furosemide. The new compound was also uricosuric and diuretic in chimpanzees, although the potency of the uricosuric activity was similar to that of probenecid and less than that of indacrinone. Thus, it seems that S-8666 is a different type of uricosuric diuretic from known agents which have already been tried in humans.