SIRT1 attenuates sepsis-induced acute kidney injury via Beclin1 deacetylation-mediated autophagy activation

Our previous studies showed that silent mating-type information regulation 2 homologue-1 (SIRT1, a deacetylase) upregulation could attenuate sepsis-induced acute kidney injury (SAKI). Upregulated SIRT1 can deacetylate certain autophagy-related proteins (Beclin1, Atg5, Atg7 and LC3) in vitro. However, it remains unclear whether the beneficial effect of SIRT1 is related to autophagy induction and the underlying mechanism of this effect is also unknown. In the present study, caecal ligation and puncture (CLP)-induced mice, and an LPS-challenged HK-2 cell line were established to mimic a SAKI animal model and a SAKI cell model, respectively. Our results demonstrated that SIRT1 activation promoted autophagy and attenuated SAKI. SIRT1 deacetylated only Beclin1 but not the other autophagy-related proteins in SAKI. SIRT1-induced autophagy and its protective effect against SAKI were mediated by the deacetylation of Beclin1 at K430 and K437. Moreover, two SIRT1 activators, resveratrol and polydatin, attenuated SAKI in CLP-induced septic mice. Our study was the first to demonstrate the important role of SIRT1-induced Beclin1 deacetylation in autophagy and its protective effect against SAKI. These findings suggest that pharmacologic induction of autophagy via SIRT1-mediated Beclin1 deacetylation may be a promising therapeutic approach for future SAKI treatment.

Umbilical Cord-Derived CD362+ Mesenchymal Stromal Cells Attenuate Polymicrobial Sepsis Induced by Caecal Ligation and Puncture

Mesenchymal stromal cells (MSCs) have a multimodal, immunomodulatory mechanism of action and are now in clinical trials for single organ and systemic sepsis. However, a number of practicalities around source, homogeneity and therapeutic window remain to be determined. Here, we utilised conditioned medium from CD362+-sorted umbilical cord-human MSCs (UC-hMSCs) for a series of in vitro anti-inflammatory assays and the cryopreserved MSCs themselves in a severe (Series 1) or moderate (Series 2+3) caecal ligation and puncture (CLP) rodent model. Surviving animals were assessed at 48 h post injury induction. MSCs improved human lung, colonic and kidney epithelial cell survival following cytokine activation. In severe systemic sepsis, MSCs administered at 30 min enhanced survival (Series 1), and reduced organ bacterial load. In moderate systemic sepsis (Series 2), MSCs were ineffective when delivered immediately or 24 h later. Of importance, MSCs delivered 4 h post induction of moderate sepsis (Series 3) were effective, improving serum lactate, enhancing bacterial clearance from tissues, reducing pro-inflammatory cytokine concentrations and increasing antimicrobial peptides in serum. While demonstrating benefit and immunomodulation in systemic sepsis, therapeutic efficacy may be limited to a specific point of disease onset, and repeat dosing, MSC enhancement or other contingencies may be necessary.

Hypothermia effects on liver and kidney oxidative stress parameters in an experimental model of sepsis in rats

IntroductionOxidative stress (OS) seems to be an important mediator of cellular injury, from which sepsis can proceed. Studies have demonstrated the protective effect of controlled hypothermia in sepsis. This study aimed to evaluate its effects on OS parameters in rat hepatic and renal tissue septic after caecal ligation and puncture (CLP).Material and MethodsThree groups were appointed (10 rats/group): C (control), SN (sepsis normothermic), and SH (sepsis hypothermic). Ten hours from CLP, the liver and kidneys were harvested and total protein concentration, superoxide dismutase (SOD), glutathione peroxidase (GPx) activities, lipid peroxidation level (malondialdehyde (MDA), carbonylated proteins (2,4-dinitrophenylhydrazine (DNPH), and fatty acid profile were analysed.ResultsSepsis significantly increased SOD and GPx activities in the liver, regardless of the temperature. In renal tissue, GPx activity increased significantly in normothermic conditions and SOD tended to decrease in hypothermic conditions. MDA and DNPH concentrations increase in both tissues after CLP. Hypothermia significantly lowered MDA in the liver but only changed it insignificantly in the kidneys. The DNPH in the liver and kidneys was significantly lower in hypothermic conditions. The unsaturated-to-saturated fatty acids ratio was significantly lower in sepsis, and the fall in temperature raised this ratio.ConclusionExperimentally induced sepsis in rats enhances OS in the liver and kidneys. The effect of hypothermia on OS indices is dependent on the type of tissue.

Transient receptor potential melastatin 2–mediated heme oxygenase-1 has a role for bacterial clearance by regulating autophagy in peritoneal macrophages during polymicrobial sepsis

Our previous study indicated an important protective role of transient receptor potential melastatin 2 (TRPM2) in controlling bacterial clearance in macrophages during polymicrobial sepsis by regulating heme oxygenase-1. Autophagy is necessary for macrophages to kill invasive bacteria. In the present study, TRPM2 knockout (KO) mice show decreased heme oxygenase-1 and autophagy in peritoneal macrophages after caecal ligation and puncture surgery. Caecal ligation and puncture-induced autophagy in peritoneal macrophages is dependent on heme oxygenase-1. TRPM2 KO mice treated with heme oxygenase-1 inducer before caecal ligation and puncture significantly increase autophagy of peritoneal macrophages, bacterial clearance rate and survival rate. In addition, TRPM2 KO mice treated with heme oxygenase-1 inducer before caecal ligation and puncture significantly attenuate organ injury and systemic inflammation. These improvements are reversed by autophagy inhibitor. Therefore, our findings suggest that TRPM2-mediated heme oxygenase-1 has a role for bacterial clearance possibly by regulating autophagy in peritoneal macrophages during polymicrobial sepsis.

Cystathionine-Gamma-Lyase-Derived Hydrogen Sulfide-Regulated Substance P Modulates Liver Sieve Fenestrations in Caecal Ligation and Puncture-Induced Sepsis

Cystathionine-γ-lyase (CSE) is a hydrogen sulfide (H2S)-synthesizing enzyme that promotes inflammation by upregulating H2S in sepsis. Liver sinusoidal endothelial cells (LSECs) are fenestrated endothelial cells (liver sieve) that undergo alteration during sepsis and H2S plays a role in this process. Substance P (SP) is encoded by the preprotachykinin A (PPTA) gene, and promotes inflammation in sepsis; however, its regulation by H2S is poorly understood. Furthermore, the interaction between H2S and SP in modulating LSEC fenestrations following sepsis remains unclear. This study aimed to investigate whether CSE/H2S regulates SP and the neurokinin-1 receptor (NK-1R) and modulates fenestrations in LSECs following caecal ligation and puncture (CLP)-induced sepsis. Here we report that the absence of either CSE or H2S protects against liver sieve defenestration and gaps formation in LSECs in sepsis by decreased SP-NK-1R signaling. Following sepsis, there is an increased expression of liver CSE and H2S synthesis, and plasma H2S levels, which were aligned with higher SP levels in the liver, lungs and plasma and NK-1R in the liver and lungs. The genetic deletion of CSE led to decreased sepsis-induced SP and NK-1R in the liver, lungs and plasma SP suggesting H2S synthesized through CSE regulates the SP-NK-1R pathway in sepsis. Further, mice deficient in the SP-encoding gene (PPTA) preserved sepsis-induced LSEC defenestration and gaps formation, as seen by maintenance of patent fenestrations and fewer gaps. In conclusion, CSE/H2S regulates SP-NK-1R and modulates LSEC fenestrations in sepsis.

The Role of Oxidative Stress in Decreased Acetylcholinesterase Activity at the Neuromuscular Junction of the Diaphragm during Sepsis

Our recent study demonstrated that acetylcholinesterase (AChE) activity at the neuromuscular junction (NMJ) of the diaphragm decreased during sepsis. However, the mechanisms were not clearly identified. In this study, we aimed to investigate whether the decreased AChE activity was related to oxidative stress by observing AChE activity in different grades of sepsis induced by caecal ligation and puncture (CLP). At 24 h after surgery, an assay of thiobarbituric acid reactive species (TBARS) and protein carbonyls, as well as the myeloperoxidase (MPO), superoxide dismutase (SOD), and catalase (CAT) activity, was conducted. AChE activity was measured by biochemical and histological detection. AChE and CAT activity in the diaphragm decreased, while the contents of TBARS and protein carbonyls, the activity of MPO and SOD, and the SOD/CAT ratios increased. The above changes were much more significant in the mid-grade septic group than in the low-grade septic group. The colour of the AChE activity staining at the NMJ gradually lightened from the sham surgery group to the mid-grade septic group. AChE activity was significantly negatively correlated with the levels of TBARS and protein carbonyls. We consider that oxidative stress might be responsible for decreased AChE activity in the diaphragms of rats induced with sepsis.