ABSTRACT
[This corrects the article DOI: 10.3389/fimmu.2023.1183768.].
ABSTRACT
Phagocytosis plays vital roles in injury and repair, while its regulation by properdin and innate repair receptor, a heterodimer receptor of erythropoietin receptor (EPOR)/ß common receptor (ßcR), in renal ischaemia-reperfusion (IR) remains unclear. Properdin, a pattern recognition molecule, facilitates phagocytosis by opsonizing damaged cells. Our previous study showed that the phagocytic function of tubular epithelial cells isolated from properdin knockout (PKO) mouse kidneys was compromised, with upregulated EPOR in IR kidneys that was further raised by PKO at repair phase. Here, helix B surface peptide (HBSP), derived from EPO only recognizing EPOR/ßcR, ameliorated IR-induced functional and structural damage in both PKO and wild-type (WT) mice. In particular, HBSP treatment led to less cell apoptosis and F4/80+ macrophage infiltration in the interstitium of PKO IR kidneys compared to the WT control. In addition, the expression of EPOR/ßcR was increased by IR in WT kidneys, and furthered increased in IR PKO kidneys, but greatly reduced by HBSP in the IR kidneys of PKO mice. HBSP also increased PCNA expression in IR kidneys of both genotypes. Moreover, iridium-labelled HBSP (HBSP-Ir) was localized mainly in the tubular epithelia after 17-h renal IR in WT mice. HBSP-Ir also anchored to mouse kidney epithelial (TCMK-1) cells treated by H2O2. Both EPOR and EPOR/ßcR were significantly increased by H2O2 treatment, while further increased EPOR was showed in cells transfected with small interfering RNA (siRNA) targeting properdin, but a lower level of EPOR was seen in EPOR siRNA and HBSP-treated cells. The number of early apoptotic cells was increased by EPOR siRNA in H2O2-treated TCMK-1, but markedly reversed by HBSP. The phagocytic function of TCMK-1 cells assessed by uptake fluorescence-labelled E.coli was enhanced by HBSP dose-dependently. Our data demonstrate for the first time that HBSP improves the phagocytic function of tubular epithelial cells and kidney repair post IR injury, via upregulated EPOR/ßcR triggered by both IR and properdin deficiency.
Subject(s)
Properdin , Reperfusion Injury , Mice , Animals , Properdin/genetics , Hydrogen Peroxide , Kidney , Reperfusion Injury/genetics , Ischemia , Epithelial Cells , Phagocytosis/genetics , RNA, Small InterferingABSTRACT
Properdin, a positive regulator of complement alternative pathway, participates in renal ischemia-reperfusion (IR) injury and also acts as a pattern-recognition molecule affecting apoptotic T-cell clearance. However, the role of properdin in tubular epithelial cells (TECs) at the repair phase post IR injury is not well defined. This study revealed that properdin knockout (PKO) mice exhibited greater injury in renal function and histology than wild-type (WT) mice post 72-h IR, with more apoptotic cells and macrophages in tubular lumina, increased active caspase-3 and HMGB1, but better histological structure at 24 h. Raised erythropoietin receptor by IR was furthered by PKO and positively correlated with injury and repair markers. Properdin in WT kidneys was also upregulated by IR, while H2O2-increased properdin in TECs was reduced by its small-interfering RNA (siRNA), with raised HMGB1 and apoptosis. Moreover, the phagocytic ability of WT TECs, analyzed by pHrodo Escherichia coli bioparticles, was promoted by H2O2 but inhibited by PKO. These results were confirmed by counting phagocytosed H2O2-induced apoptotic TECs by in situ end labeling fragmented DNAs but not affected by additional serum with/without properdin. Taken together, PKO results in impaired phagocytosis at the repair phase post renal IR injury. Properdin locally produced by TECs plays crucial roles in optimizing damaged cells and regulating phagocytic ability of TECs to effectively clear apoptotic cells and reduce inflammation.
