Males are much more susceptible to ischemia/reperfusion (I/R)-induced kidney injury when compared with females. Recently we reported that the presence of testosterone, rather than the absence of estrogen, plays a critical role in gender differences in kidney susceptibility to I/R injury in mice. Although reactive oxygen species and antioxidant defenses have been implicated in I/R injury, their roles remain to be defined. Here we report that the orchiectomized animal had significantly less lipid peroxidation and lower hydrogen peroxide levels in the kidney 4 and 24 h after 30 min of bilateral renal ischemia when compared with intact or dihydrotestosterone-treated orchiectomized males. The post-ischemic kidney expression and activity of manganese superoxide dismutase (MnSOD) in orchiectomized mice was much greater than in intact or dihydrotestosterone-administered orchiectomized mice. Four hours after 30 min of bilateral ischemia, superoxide formation was significantly lower in orchiectomized mice than in intact mice. In Madin-Darby canine kidney cells, a kidney epithelial cell line, 1 mM H 2 O 2 decreased MnSOD activity, an effect that was potentiated by pretreatment with dihydrotestosterone. Orchiectomy prevented the post-ischemic decrease of catalase activity. Treatment of male mice with manganese(III) tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP), a SOD mimetic, reduced the post-ischemic increase of plasma creatinine, lipid peroxidation, and tissue hydrogen peroxide. These results suggest that orchiectomy accelerates the post-ischemic activation of MnSOD and reduces reactive oxygen species and lipid peroxidation, resulting in reduced kidney susceptibility to I/R injury.Gender differences in disease susceptibility have been well characterized in many cardiovascular diseases (1-3). The increased risk for cardiovascular diseases in men and postmenopausal women (4) has been attributed primarily to lack of estrogen-mediated protection (5-7). Recently we demonstrated that male mice are much more susceptible to kidney ischemia/reperfusion (I/R) 5 injury when compared with female mice (8), and that orchiectomy decreases kidney susceptibility to I/R injury (9), whereas ovariectomy has no effect on kidney susceptibility to I/R injury (8). Testosterone administration to orchiectomized male or female mice reverses the protective phenotype, increasing susceptibility to kidney I/R injury. We concluded that the presence of testosterone, rather than the absence of estrogen, plays a critical role in the gender differences in kidney susceptibility to I/R injury. The detailed molecular mechanisms responsible for this testosterone effect remain to be defined.Ischemia/reperfusion markedly increases the production of reactive oxygen species (ROS) including superoxide anions, hydroxyl radicals, hypochlorous acid, hydrogen peroxide, and peroxynitrite (10). The abnormal excessive production of ROS results in lipid peroxidation, leukocyte activation, endothelial cell damage, and cytokine production, all of which contribute to tissue ...

No abstract

Past studies have identified a number of distinct mechanisms that contribute to the resistance of melanoma cells against apoptosis induced by TNF-related apoptosis-inducing ligand (TRAIL). In this report we show that cystatin B is another endogenous inhibitor of TRAIL-induced apoptosis. Cystatin B-deficient melanoma cell lines established by shRNA knockdown displayed increased apoptosis that was associated with enhanced activation of caspase-8 induced by TRAIL. This was not related to the inhibitory effect of cystatin B on the lysosomal cysteine proteases, cathepsin B and L, as they did not have a role in TRAIL-induced apoptosis in most melanoma cell lines even when cystatin B was inhibited. Instead, sensitization of melanoma cells to TRAIL-induced apoptosis by inhibition of cystatin B appeared associated with decreased stability of FLIP L as the levels of FLIP L were reduced because of shortened half-life time in melanoma cells deficient in cystatin B. In contrast, over-expression of cystatin B increased the levels of FLIP L , decreased the amount of the E3 ligase Itch associated with FLIP L , and reduced FLIP L ubiquitination. Inhibition of Itch by siRNA restored the levels of FLIP L and blocked sensitization to TRAIL-induced apoptosis associated with deficiency in cystatin B. Taken together, these results indicate that cystatin B regulates Itch-mediated degradation of FLIP L and thereby TRAIL-induced apoptosis in melanoma cells.

No abstract

No abstract