Iron signature in asbestos-induced malignant pleural mesothelioma: A population-based autopsy study.

Malignant pleural mesothelioma (MPM) is an aggressive cancer with poor prognosis. The development of MPM is frequently linked to inhalation of asbestos fibers. A genetic component of susceptibility to this disease is suggested by the observation that some individuals develop MPM following lower doses of asbestos exposure, whereas others exposed to higher quantities do not seem to be affected. This hypothesis is supported also by frequent reports of MPM familial clustering. Despite the widely recognized role of iron (Fe) in cellular asbestos-induced pulmonary toxicity, the role of the related gene polymorphisms in the etiology of MPM has apparently not been evaluated. Eighty-six single-nucleotide polymorphisms (SNPs) of 10 Fe-metabolism genes were examined by exploiting formalin-fixed paraffin-embedded postmortem samples from 77 patients who died due to MPM (designated AEM) and compared with 48 who were exposed to asbestos but from died in old age of cause other than asbestos (designated AENM). All subjects showed objective signs of asbestos exposure. Three SNPs, localized in the ferritin heavy polypeptide, transferrin, and hephaestin genes, whose frequencies were distributed differently in AEM and AENM populations, were identified. For ferritin and transferrin the C/C and the G/G genotypes, respectively, representing intronic polymorphisms, were significantly associated with protection against MPM and need to be considered as possible genetic markers of protection. Similarly, the C/C hephaestin SNP, a missense variation of this multicopper ferroxidase encoding gene, may be related, also functionally, with protection against MPM. In conclusion, it is proposed that three Fe metabolism-associated genes, significantly associated with protection against development of MPM, may serve as protective markers for this aggressive tumor.

Non peptidic urotensin II antagonists: perspectives for a new class of drugs.

Urotensin II (U-II) is a cyclic peptide isolated from a fish. Subsequently, human U-II and its receptor were identified. In rat thoracic aorta U-II triggers powerful vasoconstrictor activity. However, the constrictor response to U-II appears to be variable and highly dependent on the vascular bed examined. Vasoconstriction is not its only effect; U-II and its receptor have been demonstrated in the central nervous system, where U-II induces a cardiovascular, behavioural, motor and endocrine response and in the kidney, where it seems to influence renal hemodynamics but also salt and water excretion, in rat pancreas where it inhibits insulin secretion, in the heart where it seems to play a role in cardiac hypertrophy and fibrosis. In humans high plasma or urine levels of U-II have been described in some pathologic conditions. Peptidic and non peptidic UT receptor antagonists have been synthesized and their effects have been evaluated particularly in animal models of diabetes and heart failure. After promising results in animal models, palosuran, a non peptidic U-II antagonist has been administered also in diabetic patients to evaluate its potential nephroprotective activity. This review presents the data available on the U-II system and its role in physiological and pathological conditions, together with data regarding palosuran and other non peptidic and peptidic U-II antagonists.

Antihypertensive treatment and renal damage: amlodipine exerts protective effect through the polyol pathway.

Besides generating renal damage, hypertension plays an important role in the progression of diabetic nephropathy. The fructose-fed rat is a well-established model both of high blood pressure and renal impairment, which is similar to diabetic nephropathy. To clarify the relationship between hypertension, glucose metabolism, and kidney remodeling, we investigated the renal level of Glut 1 and Glut 5, their relation to fibrosis and the effects of an antihypertensive drug on renal damage. Twenty-four male WK rats were divided into three groups: 8 animals received a fructose-enriched diet, 8 a control diet, and 8 animals a high-fructose diet plus amlodipine (5 mg/Kg). After six weeks of treatment, we observed a significant increase in Glut 5, fibronectin, and sorbitol in fructose-fed rats compared with control and amlodipine-treated animals; there was a positive correlation between Glut 5 and fibronectin levels (r = 0.63). Glut 1 levels were similar in all three groups, whereas collagen IV was higher in fructose-fed rats; amlodipine prevented the increase of collagen IV and sorbitol. Collagen I was statistically higher in the fructose group than in the other two groups. Therefore, prolonged fructose feeding results in renal fibrosis via polyol pathway overactivity that can be prevented by means of an antihypertensive drug.

Nephroprotective effect of bosentan in diabetic rats.

Previous studies have suggested that endothelins could be involved in the pathogenesis of target organ damage in diabetes. The aim of this study was to evaluate the possible protective effect of Bosentan, an antagonist of endothelin receptor, on the kidney of diabetic rats. The study comprised a control group of 10 WKY rats and a group of 22 WKY rats in which diabetes was induced by streptozotocin i.v.; 10 rats were the control group. Diabetic rats received insulin and mean blood glucose was approximately mS 400 mg/dl throughout the study; they were divided into two groups: 11 rats received Bosentan 100 mg/kg/die by gastric gavage and 11 received vehicle for 1 month. Twenty-four hour urine collection was performed before and at the end of the study. Urinary protein excretion rate was expressed as microg urinary protein/mg urinary creatinine. The renal collagen I, fibronectin, and TGFbeta were evaluated by means of immunochemistry. The statistical analysis of the results demonstrates that Bosentan has prevented the increase in urinary protein excretion and that of renal immunoreactive collagen I, fibronectin, and TGFbeta induced by diabetes without reducing blood pressure. This study suggests a new clinical application for the antagonists of endothelin receptors.

Enrasentan, an antagonist of endothelin receptors.

Endothelins are powerful vasoconstrictor agents produced by endothelial cells and identified by Yanagisawa et al. in 1988. Two types of receptors for endothelins have been identified: ET(A) receptors are located on smooth muscle cells of the vascular wall and are responsible for endothelin-induced vasoconstriction while ET(B) receptors are located on endothelial cells and induce these cells to release NO and prostacyclin. Moreover, these peptides not only cause a potent and prolonged vasoconstriction but are also known to enhance cell proliferation and to stimulate extracellular matrix accumulation. High levels of plasma or tissue endothelins have been found in patients with heart failure, diabetes, stroke, primary pulmonary hypertension, liver cirrhosis and other diseases. Given these effects of endothelins, blocking their receptors might be a new way to reduce blood pressure and to treat other illnesses. Accordingly, many endothelin antagonists have been developed and evaluated in animals and humans. Enrasentan is a mixed ET(A) and ET(B) receptor antagonist with a higher affinity for ET(A) receptors, although it cannot be considered a selective antagonist. In an animal model of hypertension and cardiac hypertrophy the drug has reduced blood pressure, prevented cardiac hypertrophy and preserved myocardial function. In rats with hyperinsulinemia and hypertension enrasentan normalized blood pressure and prevented cardiac and renal damage. In rats with stroke the drug reduced the ischemic area in the brain. Enrasentan has been added to conventional treatment in patients with heart failure (NYHA Class 2-3) and no addictive effect of the drug has been observed. This is in contrast with results obtained in animal models and still has not been explained. In conclusion, many possible clinical applications can be suggested for this drug, but further studies are necessary to better evaluate its therapeutic efficacy.

Antihypertensive treatment with enrasentan (SB217242) in an animal model of hypertension and hyperinsulinemia.

Enrasentan is an antagonist of endothelin (ET) receptors. Previous studies have shown that antagonism of ET receptors might represent a new approach to the treatment of hypertension. Rats with a high-fructose diet (HFD) develop hyperinsulinemia, hypertriglyceridemia, and hypertension; renal and cardiac damage. The aim of this study was to evaluate whether enrasentan could reverse the hypertension and reduce the target organ damage induced by an HFD. Fifty-five WKY rats were divided into 6 groups; 35 animals received HFD for a month; thereafter 5 animals were killed, and the others were treated either with enrasentan (n = 10), hydralazine (n = 10), or placebo (n = 10) for a further month while on the HFD. Twenty animals were kept on a standard diet throughout the study; either placebo (n = 10) or enrasentan (n = 10) was administered during the second month. Enrasentan and hydralazine completely eliminated the HFD-induced increase in blood pressure; however, only enrasentan reduced the renal and cardiac damage caused by the diet. In conclusion, enrasentan was effective both in normalizing blood pressure and in reducing renal and cardiac damage; the organ protection cannot be attributed solely to the antihypertensive effect, because it was absent in the case of hydralazine, despite successful control of blood pressure.

Role of nitric oxide in the early renal changes induced by high fructose diet in rats.

BACKGROUND: Early glomerular hypertrophy and late glomerulosclerosis have been observed in rats fed high fructose diet (HFD), comparable with those of diabetic rats. Several studies suggest a role for nitric oxide (NO) in the pathogenesis of renal damage in diabetes. This study investigated the possible role of NO in the pathogenesis of HFD-induced glomerular changes. METHODS: Three study protocols were adopted. In the first, 20 rats were divided into two groups to evaluate the effect of HFD on glomerular size and on the urinary excretion of NO. In the second, the glomerular size was evaluated in 40 rats divided into four groups receiving: (1) standard diet (SD); (2) HFD; (3) HFD + L-NAME, and (4) SD + L-NAME for 1 month. In the third, the renal expression of inducible enzyme (iNOS) was compared in 10 rats on HFD and in 10 controls after a 1-month diet. RESULTS: The results showed: (1) increased urinary excretion of NO and glomerular size, both induced by HFD; (2) prevention by L-NAME of the HFD-increased glomerular size, and (3) increased iNOS expression in the kidneys of rats fed HFD. CONCLUSION: These results suggest a role for NO in the pathogenesis of the early renal changes induced by HFD.