ABSTRACT
BACKGROUND@#Studies have reported mitophagy activation in renal tubular epithelial cells (RTECs) in acute kidney injury (AKI). Phosphatase and tensin homolog-induced putative kinase 1 (PINK1) and E3 ubiquitin-protein ligase Parkin are involved in mitophagy regulation; however, little is known about the role of PINK1-Parkin mitophagy in septic AKI. Here we investigated whether the PINK1-Parkin mitophagy pathway is involved in septic AKI and its effects on cell apoptosis in vitro and on renal functions in vivo.@*METHODS@#Mitophagy-related gene expression was determined using Western blot assay in human RTEC cell line HK-2 stimulated with bacterial lipopolysaccharide (LPS) and in RTECs from septic AKI rats induced by cecal ligation and perforation (CLP). Autophagy-related ultrastructural features in rat RTECs were observed using electron microscopy. Gain- and loss-of-function approaches were performed to investigate the role of the PINK1-Parkin pathway in HK-2 cell mitophagy. Autophagy activators and inhibitors were used to assess the effects of mitophagy modulation on cell apoptosis in vitro and on renal functions in vivo.@*RESULTS@#LPS stimulation could significantly induce LC3-II and BECN-1 protein expression (LC3-II: 1.72 ± 0.05 vs. 1.00 ± 0.05, P < 0.05; BECN-1: 5.33 ± 0.57 vs. 1.00 ± 0.14, P < 0.05) at 4 h in vitro. Similarly, LC3-II, and BECN-1 protein levels were significantly increased and peaked at 2 h after CLP (LC3-II: 3.33 ± 0.12 vs. 1.03 ± 0.15, P < 0.05; BECN-1: 1.57 ± 0.26 vs. 1.02 ± 0.11, P < 0.05) in vivo compared with those after sham operation. Mitochondrial deformation and mitolysosome-mediated mitochondria clearance were observed in RTECs from septic rats. PINK1 knockdown significantly attenuated LC3-II protein expression (1.35 ± 0.21 vs. 2.38 ± 0.22, P < 0.05), whereas PINK1 overexpression markedly enhanced LC3-II protein expression (2.07 ± 0.21 vs. 1.29 ± 0.19, P < 0.05) compared with LPS-stimulated HK-2 cells. LPS-induced proapoptotic protein expression remained unchanged in autophagy activator-treated HK-2 cells and was significantly attenuated in PINK1-overexpressing cells, but was remarkably upregulated in autophagy inhibitor-treated and in PINK1-depleted cells. Consistent results were observed in flow cytometric apoptosis assay and in renal function indicators in rats.@*CONCLUSION@#PINK1-Parkin-mediated mitophagy might play a protective role in septic AKI, serving as a potential therapeutic target for septic AKI.
ABSTRACT
Background@#Studies have reported mitophagy activation in renal tubular epithelial cells (RTECs) in acute kidney injury (AKI). Phosphatase and tensin homolog-induced putative kinase 1 (PINK1) and E3 ubiquitin-protein ligase Parkin are involved in mitophagy regulation; however, little is known about the role of PINK1-Parkin mitophagy in septic AKI. Here we investigated whether the PINK1-Parkin mitophagy pathway is involved in septic AKI and its effects on cell apoptosis in vitro and on renal functions in vivo.@*Methods@#Mitophagy-related gene expression was determined using Western blot assay in human RTEC cell line HK-2 stimulated with bacterial lipopolysaccharide (LPS) and in RTECs from septic AKI rats induced by cecal ligation and perforation (CLP). Autophagy-related ultrastructural features in rat RTECs were observed using electron microscopy. Gain- and loss-of-function approaches were performed to investigate the role of the PINK1-Parkin pathway in HK-2 cell mitophagy. Autophagy activators and inhibitors were used to assess the effects of mitophagy modulation on cell apoptosis in vitro and on renal functions in vivo.@*Results@#LPS stimulation could significantly induce LC3-II and BECN-1 protein expression (LC3-II: 1.72 ± 0.05 vs. 1.00 ± 0.05, P < 0.05; BECN-1: 5.33 ± 0.57 vs. 1.00 ± 0.14, P < 0.05) at 4 h in vitro. Similarly, LC3-II, and BECN-1 protein levels were significantly increased and peaked at 2 h after CLP (LC3-II: 3.33 ± 0.12 vs. 1.03 ± 0.15, P < 0.05; BECN-1: 1.57 ± 0.26 vs. 1.02 ± 0.11, P < 0.05) in vivo compared with those after sham operation. Mitochondrial deformation and mitolysosome-mediated mitochondria clearance were observed in RTECs from septic rats. PINK1 knockdown significantly attenuated LC3-II protein expression (1.35 ± 0.21 vs. 2.38 ± 0.22, P < 0.05), whereas PINK1 overexpression markedly enhanced LC3-II protein expression (2.07 ± 0.21 vs. 1.29 ± 0.19, P < 0.05) compared with LPS-stimulated HK-2 cells. LPS-induced proapoptotic protein expression remained unchanged in autophagy activator-treated HK-2 cells and was significantly attenuated in PINK1-overexpressing cells, but was remarkably upregulated in autophagy inhibitor-treated and in PINK1-depleted cells. Consistent results were observed in flow cytometric apoptosis assay and in renal function indicators in rats.@*Conclusion@#PINK1-Parkin-mediated mitophagy might play a protective role in septic AKI, serving as a potential therapeutic target for septic AKI.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of apoptosis of CD4+ CD25+ regulatory T cells (Tregs) on proliferation as well as secretory function of effector T cells (Teff) and potential influence of Xuebijing injection on them in septic rats.</p><p><b>METHODS</b>A sepsis model was reproduced by cecal ligation puncture (CLP), and Wistar rats were randomly divided into the control group (n = 8), sham-operated group (n = 8), CLP group (n = 8), and Xuebijing injection treatment group (n = 8). CD4+ CD25+ Tregs in each group were separated by immunomagnetic beads isolate system on day 3, the apoptosis rate, expression of forkhead/winged helix transcription factor p3 (Foxp3) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) on Tregs were analyzed by flow cytometry, and secretion levels of interleukin (IL)-10 from Tregs were measured by ELISA. Following co-culture of CD4+ CD25+ Treg with CD4+ CD25- T cells (1:1) for 68 hours, proliferative activity of Teff was determined by MTT, and IL-2/sIL-2R alpha levels were measured by ELISA.</p><p><b>RESULTS</b>The apoptosis rate of Tregs in control group was 12.03% +/- 0.89%, which was not significantly different from sham-operated group 9.48% +/- 2.17%. The apoptosis rate of Tregs in CLP group 5.87% +/- 0.44% was lower than that in control group (P < 0.01), and treatment with Xuebijing injection markedly enhanced the apoptosis of Tregs 27.29% +/- 2.48%. Compared to CLP group, expression of Foxp3, CTLA-4, and the secretion of IL-10 of Treg were significantly lowered in Xuebijing injection group (all P < 0.01). The Teff proliferative activity in response to ConA, and IL-2 levels of Teff in CLP group were significantly suppressed compared with control group (P < 0.01), and secretion of sIL-2R alpha in the supernatants was much higher than that of the control group. In comparison to the CLP group, inhibitory rate of Teff proliferative activity and the sIL-2R alpha levels were significantly decreased, while the secretion of IL-2 was increased in Xuebijing injection group (P <0.01).</p><p><b>CONCLUSION</b>CD4+ CD25+ Tregs could markedly upregulate the suppressive function on Teff in sepsis, and treatment with Xuebijing injection effectively enhanced apoptosis of Tregs, thereby down-regulating the suppression on Teff.</p>
Subject(s)
Animals , Male , Rats , Apoptosis , Cell Proliferation , Disease Models, Animal , Drugs, Chinese Herbal , Therapeutic Uses , Rats, Wistar , Sepsis , Drug Therapy , Allergy and Immunology , T-Lymphocytes , Allergy and Immunology , Pathology , T-Lymphocytes, Regulatory , Allergy and Immunology , PathologyABSTRACT
<p><b>OBJECTIVE</b>To investigate the enhancing effect of Chinese medicine-Xuebijing injection on lipopolysaccharide (LPS) -induced apoptosis of CD4+ CD25+ regulatory T cells (Tregs) and polarization of helper T cells (Th).</p><p><b>METHODS</b>CD4+ CD25+ Tregs collected from rat spleen in vitro by immunomagnetic beads assay were divided into the control group, anti-CD3/CD28 group, anti-CD3/CD28 + LPS group, anti-CD3/CD28 + "Xuebijing injection" group and anti-CD3/CD28 + LPS + "Xuebijing injection" group. Tregs apoptosis rate and expression of winged helix transcription factor (Foxp3) in Tregs were detected by flow cytometry on 3rd post culture day. CD4+ CD25- T cells were co-cultured with CD4+ CD25- Tregs (1:1) for 68 hours with canavalin A stimulation. Interferon gamma (gamma-IFN), interleukin (IL)-4 and IL-17 in supernatants, which respectively was secreted by Th1, Th2 and Th17, were measured by ELISA.</p><p><b>RESULTS</b>Tregs apoptosis rate of anti-CD3/CD28 + LPS + "Xuebijing injection" group (45.1 +/- 2.7%) was significantly higher than that of anti-CD3/CD28 + LPS group (29.4 +/- 1.6%, P < 0.01). Meanwhile, Foxp3 expressions in Tregs in above 2 groups were 95 +/- 9 and 140 +/- 18 respectively, showing statistically significant difference between them (P < 0.01). Gamma-IFN levels secreted in anti-CD3/CD28 + LPS + "Xuebijing injection" group were significantly higher than those in anti-CD3/CD28 + LPS group (P < 0.01), while IL-4 levels had an opposite tendency compared with gamma-IFN (P < 0.05), resulting in a marked increase in the ra- tio of gamma-IFN/IL-4 in anti-CD3/CD28 + LPS + "Xuebijing injection" group (P < 0.01). In anti-CD3/ CD28 + "Xuebijing injection" group, IL-17 secretion levels were significantly decreased compared with anti-CD3/CD28 group (P < 0.05).</p><p><b>CONCLUSIONS</b>Activation of CD4+ CD25+ Tregs induced by LPS may mediate Th1 shift to Th2 response. "Xuebijing injection" can effectively regulate immune function of T cells, increase the LPS-induced apoptosis of CD4+ CD25+ Tregs as well as enhance the polarization of Th2 to Th1, thereby abating the suppressive state of cell-mediated immunity.</p>