Therapeutic Potentials of Scavenger Receptor CD36 Mediated Innate Immune Responses Against Infectious and Non-Infectious Diseases

CD36 favours fat sensing and transport to govern lipid metabolism

CD36, located on the cell membrane, transports fatty acids in response to dietary fat. It is a critical fatty acid sensor and regulator of lipid metabolism. The interaction between CD36 and lipid dysmetabolism and obesity has been identified in various models and human studies. Nevertheless, the mechanisms by which CD36 regulates lipid metabolism and the role of CD36 in metabolic diseases remain obscure. Here, we summarize the latest research on the role of membrane CD36 in fat metabolism, with emphasis on CD36-mediated fat sensing and transport. This review also critically discusses the factors affecting the regulation of CD36-mediated fat dysfunction. Finally, we review previous clinical evidence of CD36 in metabolic diseases and consider the path forward.

Extracellular Lipids in the Lung and Their Role in Pulmonary Fibrosis

Lipids are major actors and regulators of physiological processes within the lung. Initial research has described their critical role in tissue homeostasis and in orchestrating cellular communication to allow respiration. Over the past decades, a growing body of research has also emphasized how lipids and their metabolism may be altered, contributing to the development and progression of chronic lung diseases such as pulmonary fibrosis. In this review, we first describe the current working model of the mechanisms of lung fibrogenesis before introducing lipids and their cellular metabolism. We then summarize the evidence of altered lipid homeostasis during pulmonary fibrosis, focusing on their extracellular forms. Finally, we highlight how lipid targeting may open avenues to develop therapeutic options for patients with lung fibrosis.

Stomatin-knockdown effectively attenuates sepsis-induced oxidative stress and inflammation of alveolar epithelial cells by regulating CD36

Sepsis-induced acute lung injury is a type of lung disease with a high fatality rate that is characterized by acute inflammation. In the present study, the underlying role and potential mechanism of the stomatin (STOM) protein were investigated in lipopolysaccharide (LPS)-induced oxidative stress and inflammation in a mouse lung epithelial cell line, MLE-12. The expression levels of STOM and CD36 were measured using reverse transcription-quantitative PCR and western blotting. Subsequently, the expression levels of STOM and CD36 in LPS-treated MLE-12 cells were knocked down or overexpressed, respectively, via transfection with a small interfering RNA-STOM or a CD36-overexpression vector. An RNA immunoprecipitation (RIP) assay was used to determine the interaction between STOM and CD36, while Cell Counting Kit-8 assay and ELISA were performed to detect cell viability and oxidative stress, respectively. Moreover, western blotting and ELISA kits were used to detect the expression levels of associated inflammatory factors. The results of the present study demonstrated that STOM expression was upregulated in MLE-12 cells treated with LPS compared with the untreated control group. According to the Search Tool for the Retrieval of Interacting Genes/Proteins database, it was predicted that STOM and CD36 had the ability to interact with each other. The predicted binding between STOM and CD36 was verified using a RIP assay. The results demonstrated that STOM positively regulated the expression of CD36. Moreover, in LPS-treated MLE-12 cells, STOM-knockdown reversed the inhibitory effects of LPS on cell viability, and the promoting effects of LPS on oxidative stress and inflammation. These aforementioned changes were alleviated by the overexpression of CD36. To conclude, the results of the present study revealed that STOM may interact with CD36 to affect the levels of oxidative stress and inflammation in LPS-treated MLE-12 cells.

CD36 Ectodomain Detects Apoptosis in Mammalian Cells

The cells that undergo apoptosis show phosphatidylserine (PS) on the cell membrane. The fluorescently labeled hCD36_ecto is staining and detecting apoptotic cells in a flow-based assay with several advantages over Annexin V. The human CD36 ectodomain (hCD36_ecto) is stable for a range of temperatures and experimental conditions and doesn't require Ca²⁺ for detecting apoptosis and specific towards PS compared to other lipids. The blocking with unlabeled hCD36_ecto reduces the staining of Annexin V-FITC for apoptotic cells, whereas R63A does not affect the binding of Annexin V- FITC to apoptotic cells. It indicates the role of CD36-PS interaction in detecting apoptotic cells. Dual-staining with hCD36_ecto-FITC/PI is universally detecting apoptosis in different nucleated cells or eryptosis in non-nucleated RBCs. Hence, our study highlights the utility of CD36 as a probe to detect apoptosis in mammalian cells. It might be a robust, economical reagent for the scientific community to facilitate their research.