β-Carotene effectively scavenges toxic nitrogen oxides: nitrogen dioxide and peroxynitrous acid

Abstractβ-Carotene absorbed 2 equimolar amounts of NO2 accompanying the complete destruction of β-carotene. Electron spin resonance study using 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl revealed that no significant amounts of NO were released by the interaction. Nitrogen atoms derived from NO2 were tightly bound to the β-carotene molecules. Destruction of β-carotene was inhibited little by α-tocopherol and polyunsaturated fatty esters, and slightly by ascorbyl palmitate, indicating that β-carotene was a more effective scavenger of NO2. ONOOH/ONOO− and 3-morpholinosydononimine similarly destroyed β-carotene. The results suggest that β-carotene contributes to the prevention of cytotoxicity and genotoxicity of NO2 and ONOOH/ONOO− derived from NO.©1997 Federation of European Biochemical Societies

Regeneration of Graft Livers and Limited Contribution of Extrahepatic Cells After Partial Liver Transplantation in Humans

Background Liver regeneration is still not fully understood. Partial liver transplantation (LT) can provide the opportunity to investigate the mechanisms of liver regeneration, including the contribution of extrahepatic cells to liver regeneration. Methods Of 61 patients transplanted with partial liver graft between August 1997 and October 2006, 56 patients were studied, including 49 adults and 7 children. Sequential computed tomography volumetric analysis was performed for volume measurement, while proliferating cell nuclear antigen (PCNA) labeling index was investigated for liver cell proliferation in nonprotocol liver biopsy specimens. In addition, 15 male recipients who had female liver grafts were investigated in order to detect Y chromosomes as extrahepatic cells in nonprotocol liver biopsy specimens. Results Graft volume per standard liver volume was markedly increased after adult-to-adult living-donor (LD) LT. In pediatric transplants, there was no volume increase over time. PCNA labeling index was vigorous in adult-to-adult LDLT in the early period after LDLT. No Y chromosome was evident in hepatocytes from female-donor male-recipient grafts during or after liver regeneration. However, in the cases of failing grafts of this type, many Y-chromosome-positive cells were observed in the graft liver. The character of those cells was CD34(−), CK9(−), hepatocyte-specific antigen(−), and CD68(+/−). Conclusion In adult-to-adult LDLT, vigorous liver regeneration occurs in the graft liver, demonstrated by not only volumetric but cell kinetic analysis. Involvement of extrahepatic cells in normal liver regeneration seems limited

Losartan modulates muscular capillary density and reverses thiazide diuretic-exacerbated insulin resistance in fructose-fed rats

The renin–angiotensin system (RAS) is involved in the pathogenesis of insulin sensitivity (IS). The role of RAS in insulin resistance and muscular circulation has yet to be elucidated. Therefore, this study sought to determine the mechanisms of angiotensin II receptor blockers (ARBs) and/or diuretics on IS and capillary density (CD) in fructose-fed rats (FFRs). Sprague-Dawley rats were fed either normal chow (control group) or fructose-rich chow for 8 weeks. For the last 4 weeks, FFRs were allocated to four groups: an FFR group and groups treated with the thiazide diuretic hydrochlorothiazide (HCTZ), with the ARB losartan, or both. IS was evaluated by the euglycemic hyperinsulinemic glucose clamp technique at week 8. In addition, CD in the extensor digitorum longus muscle was evaluated. Blood pressure was significantly higher in the FFRs than in the controls. HCTZ, losartan and their combination significantly lowered blood pressure. IS was significantly lower in the FFR group than in the controls and was even lower in the HCTZ group. Losartan alone or combined with HCTZ significantly increased IS. In all cases, IS was associated with muscular CD, but not with plasma adiponectin or lipids. These results indicate that losartan reverses HCTZ-exacerbated insulin resistance, which can be mediated through the modulation of muscular circulation in rats with impaired glucose metabolism

FK506 resistance of Saccharomyces cerevisiae Pdr5 and Candida albicans Cdr1 involves mutations in the transmembrane domains and extracellular loops

The 23-membered-ring macrolide tacrolimus, a commonly used immunosuppressant, also known as FK506, is a broad-spectrum inhibitor and an efflux pump substrate of pleiotropic drug resistance (PDR) ATP-binding cassette (ABC) transporters. Little, however, is known about the molecular mechanism by which FK506 inhibits PDR transporter drug efflux. Thus, to obtain further insights we searched for FK506-resistant mutants of Saccharomyces cerevisiae cells overexpressing either the endogenous multidrug efflux pump, Pdr5, or its Candida albicans orthologue, Cdr1. A simple, but powerful, screen gave 69 FK506-resistant mutants with, between them, 72 mutations in either Pdr5 (37) or Cdr1 (35). Twenty mutations were in just three Pdr5/Cdr1 equivalent amino acid positions T550/T540 and T552/S542 of extracellular loop 1 (EL1) and A723/A713 of EL3. Sixty of the 72 mutations were either in the ELs or the extracellular halves of individual transmembrane spans (TMSs), while 11 mutations were found near the centre of individual TMSs, mostly in predicted TMS-TMS contact points, and only two mutations were in the cytosolic nucleotide-binding domains of Pdr5. We propose that FK506 inhibits Pdr5 and Cdr1 drug efflux by slowing transporter opening and/or substrate release, and that FK506-resistance of Pdr5/Cdr1 drug efflux is achieved by modifying critical intramolecular contact points that, when mutated, enable the co-transport of FK506 with other pump substrates. This may also explain why the 35 Cdr1 mutations that caused FK506-insensitivity of fluconazole efflux differed from the 13 Cdr1 mutations that caused FK506-insensitivity of cycloheximide efflux