SAMHD1 Attenuates LPS-induced Acute Kidney Injury Via Alleviating Macrophage Polarization

Acute kidney injury(AKI)is a common complication in intensive care unit with high mortality.Decreased renal function and tubular necrosis are the main features of AKI.Studies have reported that AKI is accompanied by an increase in the incidence of chronic kidney disease and end-stage renal disease.The common clinical causes of AKI can be divided into prerenal(such as hypovolemia and sepsis),intrinsic(such as drugs and toxins)and postrenal(such as obstruction or malignancy),among which the most common cause of AKI is sepsis induced by Lipopolysaccharide(LPS).Macrophages play an extremely important role in the occurrence and development of AKI.aseptic a motif and HD domain protein 1(SAMHD1)play an important role in innate immunity.It has been reported that silencing SAMHD1 can promote M1-type polarization of alveolar macrophages,but whether SAMHD1 plays a role in regulating the polarization of renal macrophages during the occurrence and development of AKI has not been reported.In this study,we performed Myeloid cell-Specific SAMHD1 Knockout in wild type(WT)mice and myeloid cell-specific SAMHD1 Knockout,Lps-induced AKI model was constructed in MKO mice,and Human kidney 2(HK2)cell line was cultured in vitro.SAMHD1 expression is up-regulated in macrophages and renal tubular epithelial cells of AKI mice.Myeloid cell-specific SAMHD1 knockout aggravates LPS-induced AKI and up-regulates SAMHD1 expression in renal tubular epithelial cells.SAMHD1 in HK2 cells by inhibiting the p65 protein phosphorylation induced by LPS activation and inhibition of NF-κB signaling pathways leading to the downstream gene expression.Results1.Establishment of LPS-induced AKI model in WT miceLPS induced AKI model was established in WT mice and stained by HE.The analysis of biochemical indexes of renal function and immunohistochemical staining proved the successful construction of AKI model.2.The expression of SAMHD1 is up-regulated in kidney macrophages of AKI miceMouse renal macrophages were labeled by immunofluorescence double labeling and SAMHD1 expression was detected in macrophages.The results showed that SAMHD1 expression was up-regulated in kidney macrophages of AKI mice.3.Effects of SAMHD1 on macrophagesAKI models were constructed in WT and MKO mice and stained by HE.PAS staining;Detection of biochemical indexes of renal function;IHC experiments demonstrated increased AKI in MKO mice induced by LPS.The infiltration of renal macrophages was detected by IHC assay,and the types of macrophages in renal tissues were determined by double standard immunofluorescence method.It was found that myeloid-specific SAMHD1 knockout increased LPS-induced macrophage infiltration and promoted M1 type polarization of macrophages,but had no effect on M2 type polarization.4.The effect of SAMHD1 on renal tubular epithelial cellsUsing IHC;WB;QPCR showed that SAMHD1 expression was increased in kidney tissue of AKI mice,and the expression level of SAMHD1 in renal tubular epithelial cells was detected by double-labeled immunofluorescence assay.The results showed that SAMHD1 expression was up-regulated in renal tubular epithelial cells after LPS induction,and myeloid cell-specific SAMHD1 knockout promoted SAMHD1 expression in renal tubular epithelial cells.In anthropogenic renal tubular epithelial cells by expressing and silent SAMHD1 experiments show SAMHD1 by inhibiting p65 protein phosphorylation of inhibition of NF-κB signaling pathway activation.