Imidapril inhibits increased transforming growth factor-beta1 expression in remnant kidney model

Angiotensin receptors in Dupuytren's tissue: Implications for the pharnnacological treatment of Dupuytren's disease

The role of Angiotensin II as a pro-fibrotic mediator has been established in models of cardiac, hepatic and renal fibrosis. The administration of Angiotensin-Converting Enzyme (ACE) – inhibitors to these models results in a reduction in the myofibroblast population and collagen synthesis. In rodent excisionat wound-healing experiments, an ACE inhibitor reduced the rate of wound contraction, collagen deposition and angiogenesis. Using immunohistochemistry, the presence of Angiotensin I receptors was identified within tissue samples from patients with Dupuytren's disease. These were found to be co-localised with areas of myofibrobtast expression. This co-localisation has implications for the potential of pharmacological regulation of Dupuytren's disease. Further research is necessary to confirm whether the use of ACE-inhibitors can modulate this disease process, which until now has not been responsive to safe, effective pharmacological treatment.

Imidapril

Imidapril (Tanatril), through its active metabolite imidaprilat, acts as an ACE inhibitor to suppress the conversion of angiotensin I to angiotensin II and thereby reduce total peripheral resistance and systemic blood pressure (BP). In clinical trials, oral imidapril was an effective antihypertensive agent in the treatment of mild to moderate essential hypertension. Some evidence suggests that imidapril also improves exercise capacity in patients with chronic heart failure (CHF) and reduces urinary albumin excretion rate in patients with type 1 diabetes mellitus. Imidapril was well tolerated, with a lower incidence of dry cough than enalapril or benazepril, and is a first choice ACE inhibitor for the treatment of mild to moderate essential hypertension.

Protection of the cardiovascular system by imidapril, a versatile angiotensin-converting enzyme inhibitor

Imidapril hydrochloride (imidapril) is a long-acting, non-sulfhydryl angiotensin-converting enzyme (ACE) inhibitor, which has been used clinically in the treatment of hypertension, chronic congestive heart failure (CHF), acute myocardial infarction (AMI), and diabetic nephropathy. It has the unique advantage over other ACE inhibitors in causing a lower incidence of dry cough. After oral administration, imidapril is rapidly converted in the liver to its active metabolite imidaprilat. The plasma levels of imidaprilat gradually increase in proportion to the dose, and decline slowly. The time to reach the maximum plasma concentration (T(max)) is 2.0 h for imidapril and 9.3 h for imidaprilat. The elimination half-lives (t(1/2)) of imidapril and imidaprilat is 1.7 and 14.8 h, respectively. Imidapril and its metabolites are excreted chiefly in the urine. As an ACE inhibitor, imidaprilat is as potent as enalaprilat, an active metabolite of enalapril, and about twice as potent as captopril. In patients with hypertension, blood pressure was still decreased at 24 h after imidapril administration. The antihypertensive effect of imidapril was dose-dependent. The maximal reduction of blood pressure and plasma ACE was achieved with imidapril, 10 mg once daily, and the additional effect was not prominent with higher doses. When administered to patients with AMI, imidapril improved left ventricular ejection fraction and reduced plasma brain natriuretic peptide (BNP) levels. In patients with mild-to-moderate CHF [New York Heart Association (NYHA) functional class II-III], imidapril increased exercise time and physical working capacity and decreased plasma atrial natriuretic peptide (ANP) and BNP levels in a dose-related manner. In patients with diabetic nephropathy, imidapril decreased urinary albumin excretion. Interestingly, imidapril improved asymptomatic dysphagia in patients with a history of stroke. In the same patients it increased serum substance P levels, while the angiotensin II receptor antagonist losartan was ineffective. These studies indicate that imidapril is a versatile ACE inhibitor. In addition to its effectiveness in the treatment of hypertension, CHF, and AMI, imidapril has beneficial effects in the treatment of diabetic nephropathy and asymptomatic dysphagia. Good tissue penetration and inhibition of tissue ACE by imidapril contributes to its effectiveness in preventing cardiovascular complications of hypertension. The major advantages of imidapril are its activity in the treatment of various cardiovascular diseases and lower incidence of cough compared with some of the older ACE inhibitors.

Effect of antihypertensive therapy on renal injury in type 2 diabetic rats with hypertension

In a previous study, we demonstrated that doxazosin (DZN), an alpha(1)-adrenergic blocker, prevented proteinuria in streptozotocin diabetic rats. In this study, we investigated whether DZN would lower established proteinuria by improving glomerular sclerosis in spontaneously hypertensive corpulent rats with type 2 diabetes mellitus. DZN treatment was compared with treatment with angiotensin-converting enzyme inhibitor, lisinopril (LIS) alone, and DZN in combination with LIS. Combination therapy was used to examine any additive effect of either drug alone in the reduction of proteinuria and glomerular sclerosis. Both male and female rats age 6 months with established proteinuria were used. The rats were allocated randomly to 1 of 4 groups: untreated, DZN treated, LIS treated, or a combination of DZN and LIS treatment. Drug treatment was continued for 16 weeks. The results show that (1) either drug alone or in combination significantly lowered systolic blood pressure; (2) DZN, LIS, or combination therapy reduced albuminuria at 16 weeks of treatment from baseline by 38.61+/-5.77%, 30.70+/-4. 21%, and 42.17+/-4.77% (mean+/-SE), respectively. No difference in albuminuria was observed among the 3 groups of rats; (3) the fractional mesangial area, which was 20.55+/-3.77% in untreated rats, was significantly reduced to 11.18+/-1.32% in DZN-treated rats, with a further reduction to 8.72+/-0.64% in LIS-treated rats and to 3.48+/-0.35% in rats treated with DZN+LIS; and (4) DZN but not LIS significantly improved plasma glucose levels in spontaneously hypertensive corpulent rats (untreated 21.06+/-0.97 mmol/L versus DZN treated 15.81+/-0.93 mmol/L or DZN+LIS treated 17.38+/-1.10 mmol/L; P<0.025 to 0.005). Thus, the data suggest that 16-week treatment with either DZN or LIS improves established proteinuria and glomerular sclerosis, but combination therapy is superior to either DZN or LIS alone in preventing glomerular sclerosis in type 2 diabetic rats with hypertension.

Combined mycophenolate mofetil and losartan therapy arrests established injury in the remnant kidney

Previously it was shown that early treatment with mycophenolate mofetil (MMF) attenuated renal inflammation, glomerulosclerosis (GS), and interstitial expansion in the 5/6 ablation (NX) model. Angiotensin II antagonists also mitigate renal injury in NX, presumably by lowering glomerular pressure (P(GC)). This study investigated: (1) whether combined MMF/angiotensin II antagonists treatment affords superior protection compared with the respective monotherapies; and (2) whether this association is effective even when instituted late in the course of the disease. Adult male Munich-Wistar rats underwent NX, remaining untreated for 30 d. BP, albuminuria, and the extent of GS, interstitial expansion, and macrophage infiltration were then determined in 17 rats. The remaining 118 rats received either inert vehicle or one of the following: MMF, 10 mg/kg by gavage once daily; losartan potassium (L), 20 mg/dl in drinking water; or combined MMF/L treatment. Sixty days after ablation, untreated NX rats exhibited marked glomerular hypertension, which was attenuated by MMF and, more effectively, by either L or combined MMF/L treatment. At 120 d, hypertension and albuminuria were worsened in untreated NX rats, which exhibited intense macrophage infiltration and severe glomerular and interstitial disease. L and, to a lesser extent, MMF monotherapies attenuated these abnormalities, without preventing their progression. In rats given combined MMF/L therapy, macrophage infiltration, GS, and interstitial expansion remained at pretreatment levels. By acting on two distinct pathogenic mechanisms, combined MMF/L treatment arrested established renal injury in the NX model. Further investigation is needed to determine whether this association can prevent renal scarring in other models and in human disease.

The transforming growth factor beta system in kidney disease and repair: recent progress and future directions

Transforming growth factor beta is a multifunctional polypeptide growth factor implicated in a variety of renal diseases. The expression of transforming growth factor beta is enhanced in renal diseases and available evidence suggests that its activity in promoting the synthesis of extracellular matrix plays a crucial role in fibrotic deposition and the decline in renal function. Transforming growth factor beta is, however, also expressed in response to renal injury and may play an important role in normal repair processes. It appears that renal diseases may result from the inappropriate regulation of transforming growth factor beta expression. The determination of the factors that mediate transforming growth factor beta activity will be of primary importance in elucidating the mechanisms leading to renal disease or repair after injury. Both in-vitro and in-vivo studies have demonstrated that proteolytic activity, thrombospondin-1, elevated glucose, angiotensin II, oxidant stress and hemodynamic forces regulate transforming growth factor beta activity through both transcriptional and post-transcriptional mechanisms. In some cases, therapies that may partly disrupt renal transforming growth factor beta activity have shown promise in slowing the progression to end-stage renal disease.