Search

Abstract Background Age-related macular degeneration (AMD) is an irreversible eye disease that can cause blurred vision. Regular exercise has been suggested as a therapeutic strategy for treating AMD, but how exercise improves AMD is not yet understood. This study investigated the protective effects of developmental endothelial locus-1 (DEL-1), a myokine upregulated during exercise, on endoplasmic reticulum (ER) stress-induced injury in retinal pigment epithelial cells. Methods We evaluated the levels of AMPK phosphorylation, autophagy markers, and ER stress markers in DEL-1-treated human retinal pigment epithelial cells (hRPE) using Western blotting. We also performed cell viability, caspase 3 activity assays, and autophagosome staining. Results Our findings showed that treatment with recombinant DEL-1 dose-dependently reduced the impairment of cell viability and caspase 3 activity in tunicamycin-treated hRPE cells. DEL-1 treatment also alleviated tunicamycin-induced ER stress markers and VEGF expression. Moreover, AMPK phosphorylation and autophagy markers were increased in hRPE cells in the presence of DEL-1. However, the effects of DEL-1 on ER stress, VEGF expression, and apoptosis in tunicamycin-treated hRPE cells were reduced by AMPK siRNA or 3-methyladenine (3-MA), an autophagy inhibitor. Conclusions Our study suggests that DEL-1, a myokine, may have potential as a treatment strategy for AMD by attenuating ER stress-induced injury in retinal pigment epithelial cells.

Background: Rb3 is a ginsenoside with anti-inflammatory properties in many cell types and has been reported to attenuate inflammation-related metabolic diseases such as insulin resistance, nonalcoholic fatty liver disease, and cardiovascular disease. However, the effect of Rb3 on podocyte apoptosis under hyperlipidemic conditions, which contributes to the development of obesity-mediated renal disease, remains unclear. In the current study, we aimed to investigate the effect of Rb3 on podocyte apoptosis in the presence of palmitate and explore its underlying molecular mechanisms. Methods: Human podocytes (CIHP-1 cells) were exposed to Rb3 in the presence of palmitate as a model of hyperlipidemia. Cell viability was assessed by MTT assay. The effects of Rb3 on the expression of various proteins were analyzed by Western blotting. Apoptosis levels were determined by MTT assay, caspase 3 activity assay, and cleaved caspase 3 expression. Results: We found that Rb3 treatment alleviated the impairment of cell viability and increased caspase 3 activity as well as inflammatory markers in palmitate-treated podocytes. Treatment with Rb3 dose-dependently increased PPARδ and SIRT6 expression. Knockdown of PPARδ or SIRT6 reduced the effects of Rb3 on apoptosis as well as inflammation and oxidative stress in cultured podocytes. Conclusions: The current results suggest that Rb3 alleviates inflammation and oxidative stress via PPARδ- or SIRT6-mediated signaling, thereby attenuating apoptosis in podocytes in the presence of palmitate. The present study provides Rb3 as an effective strategy for treating obesity-mediated renal injury.

AimsMyokine developmental endothelial locus-1 (DEL-1) has been documented to alleviate inflammation and endoplasmic reticulum (ER) stress in various cell types. However, the effects of DEL-1 on inflammation, ER stress, and apoptosis in tenocytes remain unclear.MethodsHuman primary tenocytes were cultured in palmitate (400 μM) and palmitate plus DEL-1 (0 to 2 μg/ml) conditions for 24 hours. The expression levels of ER stress markers and cleaved caspase 3, as well as phosphorylated 5' adenosine monophosphate-activated protein kinase (AMPK) and autophagy markers, were assessed by Western blotting. Autophagosome formation was measured by staining with monodansylcadaverine, and apoptosis was determined by cell viability assay and caspase 3 activity assay.ResultsWe found that treatment with DEL-1 suppressed palmitate-induced inflammation, ER stress, and apoptosis in human primary tenocytes. DEL-1 treatment augmented LC3 conversion and p62 degradation as well as AMPK phosphorylation. Moreover, small interfering RNA for AMPK or 3-methyladenine (3-MA), an autophagy inhibitor, abolished the suppressive effects of DEL-1 on inflammation, ER stress, and apoptosis in tenocytes. Similar to DEL-1, 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), an activator of AMPK, also attenuated palmitate-induced inflammation, ER stress, and apoptosis in tenocytes, which 3-MA reversed.ConclusionThese results revealed that DEL-1 suppresses inflammation and ER stress, thereby attenuating tenocyte apoptosis through AMPK/autophagy-mediated signalling. Thus, regular exercise or administration of DEL-1 may directly contribute to improving tendinitis exacerbated by obesity and insulin resistance.Cite this article: Bone Joint Res 2022;11(12):854–861.