Innate immune molecule surfactant protein D attenuates sepsis-induced acute kidney injury through modulating apoptosis and NFκB-mediated inflammation

Bovine pulmonary surfactant alleviates inflammation and epithelial cell apoptosis in the early phase of lipopolysaccharide-induced acute lung injury in rats

We investigate the impact of bovine pulmonary surfactant (PS) on LPS-induced ALI in vitro and in vivo to improve recognition and prevent mortality in sepsis-induced ALI. Primary alveolar type II (AT2) cells were treated with LPS alone or in combination with PS. Cell morphology observation, CCK-8 proliferation assay, flow cytometry apoptosis assay, and ELISA for inflammatory cytokine levels were performed at different time points after treatment. An LPS-induced ALI rat model was established and treated with vehicle or PS. Lung wet/dry weight ratio, histopathological changes, lung function parameters, and serum inflammatory cytokine levels were examined 6 h after PS treatment. Survival analysis by Kaplan-Meier method. RNA sequencing was conducted to identify LPS-induced differentially expressed genes in rat lungs. Proapoptotic gene expression in rat lungs was determined by Western blot. LPS significantly inhibited cell proliferation while promoting apoptosis of AT2 cells starting 2 h after treatment, accompanied by a significant increase in inflammatory cytokine production; PS reversed these effects. PS decreased the lung wet/dry ratio in septic rats, histological abnormalities, alterations in lung function parameters, and inflammatory cytokines production; while improving the overall survival of rats. LPS-induced differentially expressed genes were closely associated with apoptosis. PS attenuated LPS-induced upregulation of proapoptotic gene expression starting 2 h after treatment in AT2 cells while restoring lung ATPase activity in vivo. Bovine PS alleviates LPS-induced ALI in the early phase, possibly by suppressing inflammation and AT2 cell apoptosis, as a preemptive therapeutic agent for managing sepsis-induced ALI.

CHAC1 exacerbates LPS-induced ferroptosis and apoptosis in HK-2 cells by promoting oxidative stress

BACKGROUND

Sepsis-induced acute kidney injury (AKI) is a singularly grievous and life-threatening syndrome. Its pathogenesis is closely related to inflammatory response, apoptosis, oxidative stress, and ferroptosis. Cation transport regulator-like protein 1 (CHAC1), as a proapoptic factor, may be involved in apoptosis, oxidative stress, and ferroptosis. This study aimed to explore the role of CHAC1 in the lipopolysaccharide (LPS)-induced the human renal proximal tubular epithelial (HK-2) cells.

METHODS

HK-2 cells were challenged with LPS to construct a model of sepsis-induced AKI in vitro. The role of CHAC1 in the LPS-induced HK-2 cells was explored using Western blot assay, cell counting kit-8 (CCK-8), flow cytometry, and colorimetric assays. Additionally, N-acetyl cysteine (NAC) was incubated with HK-2 cells to define deeply the relation between oxidative stress and apoptosis or ferroptosis.

RESULTS

The expression of CHAC1 was enhanced in the kidney tissues of mice with sepsis--induced multiple organ dysfunction syndrome (MODS), through the Gene Expression Omnibus database (GSE60088 microarray dataset), and in the LPS-induced HK-2 cells. The cell viability was significantly reduced by LPS treatment, which was at least partly restored by the transfection of siCHAC1#1 and siCHAC1#2 but not siNC. In addition, down-regulation of CHAC1 counteracted the LPS-induced reactive oxygen species level and malonaldehyde concentrations while restored the LPS-induced glutathione concentrations. Meanwhile, interference of CHAC1 neutralized LPS-induced apoptosis rate, and the relative level of cleaved poly(ADP-ribose) polymerase (PARP)/PARP, and cleaved caspase-3/caspase-3. In addition, silencing of CHAC1 recovered the LPS-induced enhanced protein level of glutathione peroxidase 4 (GPx4) whereas antagonized the LPS-induced relative protein level of ACSL4 and that of iron. Moreover, application of NAC inverted the effect of CHAC1 on apoptosis and ferroptosis in HK-2 cells.

CONCLUSION

CHAC1 exacerbated ferroptosis and apoptosis by enhancing oxidative stress in LPS-induced HK-2 cells.

RasGRP exacerbates lipopolysaccharides-induced acute kidney injury through regulating ERKs activation

Background

Excessive inflammatory activities are reported to be the primary cause of sepsis-induced acute kidney injury (AKI). Ras guanyl nucleotide-releasing protein (RasGRP) could prevent inflammatory response. However, its role in the regulation of inflammatory response in sepsis-associated AKI remains unclear.

Methods

Wild-type or RasGRP1-deficient mice were treated with lipopolysaccharide intraperitoneally in combination with D-galactosamine to establish a mouse model of sepsis-associated AKI. Serum inflammatory cytokines were measured using enzyme-linked immunosorbent assay. The messenger RNA (mRNA) levels of interleukin 6, tumor necrosis factor, nitric oxide synthase 2, and interleukin 1β were measured using quantitative reverse-transcription polymerase chain reaction. The morphological change in kidney tubule was determined by hematoxylin-and-eosin staining. The protein levels of RasGRP, extracellular signal-regulated kinases 1 and 2 (ERK1/2), and c-Jun N-terminal kinase (JNK) were determined using Western blot.

Results

RasGRP1 mRNA and protein levels were significantly increased in patients with sepsis-related AKI compared to those in healthy subjects. RasGRP knockout markedly reduced inflammatory cytokines induced by AKI in sepsis when compared with wild-type mice. Additionally, RasGRP deficiency inhibited the phosphorylation of ERK1/2 without altering JNK expression. In conclusion, we demonstrate that RasGRP1 plays a pivotal role in sepsis-associated AKI. Downregulation of RasGRP1 could significantly inhibit inflammatory response by inhibiting the activation of ERK1/2 and mitogen-activated protein kinase pathway, thereby reducing AKI induced by sepsis.

Conclusions

Our data suggest that RasGRP exacerbates lipopolysaccharide-induced acute kidney injury through regulating ERK activation, which reveals a potential therapeutic target for the treatment of sepsis-induced AKI.

MIR210HG Aggravates Sepsis-Induced Inflammatory Response of Proximal Tubular Epithelial Cell via the NF-κB Signaling Pathway

PURPOSE

Acute kidney injury (AKI) is a serious complication of sepsis and is characterized by inflammatory response. MicroRNA-210 host gene (MIR210HG) is upregulated in human proximal tubular epithelial cells under treatment of inflammatory cytokines. This study aimed to explore the role of MIR210HG in sepsis-induced AKI.

MATERIALS AND METHODS

Cell viability was detected by a cell counting kit 8 assay. The levels of proinflammatory cytokines were detected by enzyme-linked immunosorbent assay kits. The protein levels of p65, IκBα, and p-IκBα were examined by western blot analysis. The nuclear translocation of nuclear factor kappa B (NF-κB) was detected by immunofluorescence assay. The histological changes of kidneys were analyzed by hematoxylin and eosin staining assay.

RESULTS

Lipopolysaccharide (LPS) treatment significantly inhibited cell viability and increased productions of proinflammatory cytokines in proximal tubular epithelial cells (HKC-8). Additionally, MIR210HG levels in HKC-8 cells were increased by LPS treatment. MIR210HG silencing inhibited the LPS-induced cell inflammatory response. MIR210HG activated the NF-κB signaling pathway by promoting the phosphorylation of IκBα and nuclear translocation of p65. Rescue assays revealed that the MIR210HG-induced increase of cytokines levels and decline of cell viability were rescued by QNZ treatment. Knockdown of MIR210HG decreased blood urea nitrogen, serum creatinine, and proinflammatory cytokine levels in AKI rats. Moreover, the knockdown of MIR210HG protected against AKI-induced histological changes of kidneys in rats.

CONCLUSION

MIR210HG promotes sepsis-induced inflammatory response of HKC-8 cells by activating the NF-κB signaling pathway. This novel discovery may be helpful for the improvement of sepsis-induced AKI.

TUNEL Assay: A Powerful Tool for Kidney Injury Evaluation

Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay is a long-established assay used to detect cell death-associated DNA fragmentation (3'-OH DNA termini) by endonucleases. Because these enzymes are particularly active in the kidney, TUNEL is widely used to identify and quantify DNA fragmentation and cell death in cultured kidney cells and animal and human kidneys resulting from toxic or hypoxic injury. The early characterization of TUNEL as an apoptotic assay has led to numerous misinterpretations of the mechanisms of kidney cell injury. Nevertheless, TUNEL is becoming increasingly popular for kidney injury assessment because it can be used universally in cultured and tissue cells and for all mechanisms of cell death. Furthermore, it is sensitive, accurate, quantitative, easily linked to particular cells or tissue compartments, and can be combined with immunohistochemistry to allow reliable identification of cell types or likely mechanisms of cell death. Traditionally, TUNEL analysis has been limited to the presence or absence of a TUNEL signal. However, additional information on the mechanism of cell death can be obtained from the analysis of TUNEL patterns.

Innate immune molecule surfactant protein D attenuates sepsis-induced acute kidney injury through modulating apoptosis and NFκB-mediated inflammation

The objective of this study is to investigate the mechanism whereby innate immune molecule surfactant protein D (SP-D) attenuates sepsis-induced acute kidney injury (AKI) through modulating apoptosis and nuclear factor kappa-B (NFκB)-mediated inflammation. In the present study, a mouse sepsis model was established by cecal ligation and puncture in SP-D knockout (KO) mice and wild-type (WT) mice. A sham-operated group was included as the control. The experimental materials were extracted 6 and 24 hours postoperatively. The plasma levels of tumour necrosis factor alpha (TNF-α) and MCP-1 were determined by enzyme-linked immunosorbent assay (ELISA). Apoptosis was measured by double staining with Annexin V/propidium iodide and flow cytometry. The levels of NFκB in renal tissues were measured by ELISA and Western blotting assay. Apoptosis was detected by TUNEL assays. There were no significant differences in plasma TNF-α levels between the WT sham group and the KO sham group at 6 and 24 hours postoperatively (P < .05), but the levels of TNF-α in the WT sepsis and KO sepsis groups were significantly higher than those in controls (P < .05). The levels of TNF-α in the KO sepsis group were significantly higher than those of the WT sepsis group (P < .05). TNF-α levels in the WT sepsis group and the KO sepsis group at 24 hours postoperatively were significantly higher than those at 6 hours postoperatively (P < .05). The levels of MCP-1 in the WT sepsis group and the KO sepsis group at 6 and 24 hours postoperatively were significantly higher than those in the control group (P < .05), and MCP-1 levels in the KO sepsis group were significantly higher than those in the WT sepsis group (P < .05). MCP-1 levels in the WT sepsis group and the KO sepsis group at 24 hours postoperatively were significantly higher than those at 6 hours postoperatively (P < .05). The expression of SP-D in WT kidneys was significantly lower at 6 and 24 hours postoperatively (P < .05). The number of TUNEL-positive cells in the kidneys from septic SP-D KO mice was significantly higher (P < .05). The levels of NFκB in septic mice were significantly increased at 6 and 24 hours after induction of sepsis compared with the sham-operated group compared with those of septic SP-D KO mice and WT mice (P < .05). Innate immune molecule SP-D significantly decreased plasma levels of inflammatory cytokines in mice and attenuated sepsis-induced AKI by inhibiting NFκB activity and apoptosis.