Sex differences in response to cyclosporine immunosuppression in experimental kidney transplantation

Sex as a biological variable: Mechanistic insights and clinical relevance in solid organ transplantation

Biological sex affects immunity broadly, with recognized effects on the incidence and severity of autoimmune diseases, infections, and malignancies. Consequences of sex on alloimmunity and outcomes in solid organ transplantation are less well defined. Clinical studies have shown that donor and recipient sex independently impact transplant outcomes, which are further modified by aging. Potential mechanisms have thus far not been detailed and may include hormonal, genetic, and epigenetic components. Here, we summarize relevant findings in immunity in addition to studies in clinical and experimental organ transplantation detailing the effects of biological sex on alloimmunity. Understanding both clinical impact and mechanisms is expected to provide critical insights on the complexity of alloimmune responses, with the potential to fine-tune treatment and allocation while providing a rationale to include both sexes in transplant research.

Sex differences in renal ischemia-reperfusion injury

Ischemia-reperfusion injury of the kidney is caused by the sudden and temporary obstruction of blood flow to the organ. Renal ischemia-reperfusion injury is associated with high morbidity and mortality, but effective therapies are lacking. Sexual dimorphism in renal injury has been acknowledged since the 1940s, and the possible role of sex hormones has been intensively investigated in the past decades. Clinical and experimental data demonstrate sexual differences in renal anatomy, physiology, and susceptibility to renal diseases including but not limited to ischemia-reperfusion injury. Some data suggest the protective role of female sex hormones, whereas others highlight the detrimental effect of male hormones in renal ischemia-reperfusion injury. Although the important role of sex hormones is evident, the exact underlying mechanisms remain to be elucidated. This review focuses on collecting the current knowledge about sexual dimorphism of renal ischemia-reperfusion injury, with emphasis on molecular mechanisms and potential novel therapeutic strategies.

Divergent Effects of Cyclophilin-D Inhibition on the Female Rat Heart: Acute Versus Chronic Post-Myocardial Infarction

BACKGROUND/AIMS

The mitochondrial permeability transition pore opening plays a critical role in the pathogenesis of myocardial infarction. Inhibition of cyclophilin-D (CyP-D), a key regulator of the mitochondrial permeability transition pore, has been shown to exert cardioprotective effects against ischemia-reperfusion injury on various animal models, mostly in males. However, failure of recent clinical trials requires a detailed elucidation of the cardioprotective efficacy of CyP-D inhibition. The aim of this study was to examine whether cardioprotective effects of sanglifehrin A, a potent inhibitor of CyP-D, on post-infarcted hearts depends on reperfusion.

METHODS

Acute or chronic myocardial infarction was induced by coronary artery ligation with/without subsequent reperfusion for 2 and 28 days in female Sprague-Dawley rats. Cardiac function was estimated by echocardiography. Oxygen consumption rates, ROS production, permeability transition pore opening, protein carbonylation and respiratory supercomplexes were analyzed in isolated cardiac mitochondria.

RESULTS

Sanglifehrin A significantly improved cardiac function of reperfused hearts at 2 days but failed to protect after 28 days. No protection was observed in non-reperfused post-infarcted hearts. The respiratory control index of mitochondria was significantly reduced in reperfused infarcted hearts at 2-days with no effect at 28-days post-infarction on reperfused and non-reperfused hearts. Likewise, only a minor increase in reactive oxygen species production was observed at 2-days in non-reperfused post-infarcted hearts.

CONCLUSION

This study demonstrates that CyP-D inhibition exerts cardioprotective effects in reperfused but not in non-reperfused infarcted hearts of female rats, and the effects are observed only during acute post-infarction injury.

Cross-sex transplantation alters gene expression and enhances inflammatory response in the transplanted kidneys

Kidney transplantation (KTX) is a life-saving procedure for patients with end-stage renal disease. Expression levels of many genes in the kidney vary between males and females, which may play an essential role in the sex differences in graft function. However, whether these differences are affected after cross-sex-KTX is unknown. In the present study, we assessed postoperative changes in genotype, function, and inflammatory responses of the grafts in same-sex- and cross-sex-KTX. Single kidney transplants were performed between same and different sex C57BL/6 mice paired into four combination groups: female donor/female recipient (F/F); male donor/male recipient (M/M); female donor/male recipient (F/M); and male donor/female recipient (M/F). The remnant native kidney was removed 4 days posttransplant. Expression levels of genes related to the contractility of the afferent arteriole and tubular sodium reabsorption were assessed. Same-sex-KTX did not significantly alter the magnitude or sex difference pattern of gene expression in male or female grafts. Cross-sex-KTX showed an attenuated sex difference in gene expressions. The measurements of endothelin 1, endothelin ET_A receptor, Na⁺-K^--2Cl cotransporter 2 (NKCC2), and epithelial Na⁺ channels (ENaC) subunits exhibited decreases in M/F compared with M/M and increases in F/M compared with F/F. There were no significant differences in hemodynamics or sodium excretion in response to acute volume expansion for any sex combinations. Cross-sex-KTX stimulated more robust inflammatory responses than same-sex-KTX. IL-6 and KC mRNA levels elevated 5- to 20-fold in cross-sex-KTX compared with same-sex-KTX. In conclusion, cross-sex-KTX alters gene expression levels and induces inflammatory responses, which might play an important role in long-term graft function.

Telmisartan protects 5/6 Nx rats against renal injury by enhancing nNOS-derived NO generation via regulation of PPARγ signaling

A 5/6 nephrectomized (Nx) rat model was employed to address the impact of telmisartan on CKD related renal injury and the underlying molecular mechanisms. It was noted that telmisartan provided protection for rats against 5/6 Nx induced lethality. Telmisartan treated 5/6 Nx rats manifested improved renal function as characterized by the higher GFR but lower urinary albumin, BUN and Scr as compared with that of control rats. Telmisartan treatment also significantly decreased systolic blood pressure and alleviated glomerulosclerosis and interstitial fibrosis. Mechanistic studies revealed that telmisartan possesses the capability to increase NO generation in the kidney. Further studies demonstrated that telmisartan promotes PPARγ expression, by which it specifically enhances nNOS expression in the kidneys after 5/6 Nx insult. Particularly, blockade of PPARγ signaling by GW9662 abolished the protective effect conferred by telmisartan, indicating that telmisartan induction of renal nNOS expression along with NO generation is dependent on PPARγ signaling. Together, our data support that telmisartan could be a promising drug for treatment of chronic kidney diseases in diverse clinical settings.

The effect of donor-recipient gender mismatch on short- and long-term graft survival in kidney transplantation: a systematic review and meta-analysis

BACKGROUND

There is no limitation of gender matching in renal transplantation. This study was intended to evaluate its effect on short- and long-term graft survival.

METHODS

PubMed, the Web of Knowledge, Medline, the Cochrane Library, and two additional Chinese databases were searched. The data were then abstracted and meta-analyzed.

RESULTS

14 studies involving 445 279 patients were included. Each study reported data on the four gender matches (male donor-male recipient, MDMR; male donor-female recipient, MDFR; female donor-male recipient, FDMR; female donor-female recipient, FDFR). The pooled risk ratios (RRs) for 0.5-, 1-, 2-, 3-, 5-, and 10-yr graft survival rates showed that the FDMR group had the worst outcomes, and when recipients were female, short-term graft survival was worse, but long-term graft survival was better. The differences between groups changed with time.

CONCLUSIONS

FDMR patients showed poor graft survival. The female recipients had worse short-term graft survival but the best long-term graft survival. This study introduces an important consideration into donor-recipient matching in renal transplantation.

Anti-apoptotic and anti-oxidant effects of grape seed proanthocyanidin extract in preventing cyclosporine A-induced nephropathy

AIM

Although the pathogenesis of cyclosporine (CsA) nephropathy is not completely understood, it is attributed to oxidative damage and apoptosis. Grape seed proanthocyanidin extract (GSPE) is a molecule with anti-oxidant and anti-apoptotic properties. Our aim was to demonstrate the effects of GSPE in preventing CsA nephropathy.

METHODS

Twenty-four Sprague-Dawley rats were divided into four groups. The control, GSPE, CsA and CsA+GSPE groups were given 1 mL olive oil, 100 mg/kg GSPE, 25 mg/kg CsA and 100 mg/kg GSPE+25 mg/kg CsA, respectively. On day 21, blood samples were taken for blood urea nitrogen (BUN), creatinine and CsA levels, and renal tissue was used for total oxidant system (TOS), total anti-oxidant system (TAS), oxidative stress index (OSI) and malondialdehyde (MDA) measurements. In addition to renal histopathology, apoptosis staining was performed on renal tissue.

RESULTS

The BUN, creatinine, TOS, OSI, MDA, histopathological score, and apoptotic index exhibited increases in the CsA group. In the CsA+GSPE group, however, BUN, creatinine, OSI, MDA, renal histopathological score and apoptotic index (AI) decreased and TAS levels increased. In addition, there was no difference between the CsA and CsA+GSPE groups with regard to CsA levels.

CONCLUSION

We demonstrated that GSPE prevents CsA nephropathy and that this effect is achieved by anti-apoptotic and anti-oxidant activity. We also achieved a significant recovery in kidney functions without affecting CsA plasma levels.

ABCB1 gene expression in peripheral blood mononuclear cells in healthy Thai males and females

We compared the expression of the ABCB1 gene in healthy male and female Thai subjects; this gene encodes the P-glycoprotein transporter in peripheral blood mononuclear cells (PBMCs). We also identified the most suitable housekeeping genes for normalization of ABCB1 expression levels in PBMCs. PBMCs from 30 females and 26 males were isolated. Total RNA was extracted, followed by reverse transcription (100 ng total RNA per sample). The internal normalization controls were actin-beta, beta-2M and GAPDH. Real-time quantitative PCR was then performed to determine the expression levels of the ABCB1 gene. The expression levels were found to be 1.5- to 2.5-fold higher in males, depending on the endogenous control used for normalization. Actin-beta was the most stable control gene and could be used as a single endogenous control for normalization of ABCB1 expression levels in PBMCs. However, more than one endogenous control genes are recommended for normalization of gene expression. We conclude that the expression levels of ABCB1 in PBMCs is influenced by gender; this helps, in part, explain the gender difference in pharmacokinetics and pharmacodynamics of drugs that are P-glycoprotein substrates. ABCB1 gene expression profiles need to be carefully interpreted with regards to the endogenous control genes that are involved.