Polystyrene microplastic-induced endoplasmic reticulum stress contributes to growth plate endochondral ossification disorder in young rat.

BACKGROUND: Previous studies on the effects of microplastics (MPs) on bone in early development are limited. This study aimed to investigate the adverse effects of MPs on bone in young rats and the potential mechanism. METHODS: Three-week-old female rats were orally administered MPs for 28 days, and endoplasmic reticulum (ER) stress inhibitor salubrinal (SAL) and ER stress agonist tunicamycin (TM) were added to evaluate the effect of ER stress on toxicity of MPs. The indicators of growth and plasma markers of bone turnover were evaluated. Tibias were analyzed using micro-computed tomography (micro-CT). Histomorphological staining of growth plates was performed, and related gene expression of growth plate chondrocytes was tested. RESULTS: After exposure of MPs, the rats had decreased growth, shortened tibial length, and altered blood calcium and phosphorus metabolism. Trabecular bone was sparse according to micro-CT inspection. In the growth plate, the thickness of proliferative zone substantial reduced while the thickness of hypertrophic zone increased significantly, and the chondrocytes were scarce and irregularly arranged according to tibial histological staining. The transcription of the ER stress-related genes BIP, PERK, ATF4, and CHOP dramatically increased, and the transcription factors involved in chondrocyte proliferation, differentiation, apoptosis, and matrix secretion were aberrant according to RT-qPCR and western blotting. Moreover, the addition of TM showed higher percentage of chondrocyte death. Administration of SAL alleviated all of the MPs-induced symptoms. CONCLUSION: These results indicated that MPs could induce growth retardation and longitudinal bone damage in early development. The toxicity of MPs may attribute to induced ER stress and impaired essential processes of the endochondral ossification after MPs exposure.

Loss of LEAP-2 alleviates obesity-induced myocardial injury by regulating macrophage polarization.

BACKGROUND: Obesity is a serious public health issue worldwide, which is a risk factor of cardiovascular disorders. Obesity has been shown to be associated with subclinical myocardial injury, increasing the risk of heart failure. Our study aims to explore novel mechanisms underlying obesity-induced myocardial injury. METHODS: Mice were fed a high-fat diet (HFD) to establish a mouse model of obesity, and serum levels of TG, TCH, LDL, CK-MB, LDH, cTnI and BNP were examined. Inflammatory response was evaluated by determining the expression and secretion of proinflammatory cytokines IL-1ß and TNF-α. Macrophage infiltration in the heart was examined by IHC staining, and H&E staining was applied to evaluate myocardial injury. Primary peritoneal macrophages were isolated from mice and treated with palmitic acid (PA). Macrophage polarization was evaluated by determine the expression of CCL2, iNOS, CD206 and arginase I via Western blot, RT-qPCR, and flow cytometry. Co-IP assays were performed to examine the interaction between LEAP-2, GHSR and ghrelin. RESULTS: Hyperlipidemia, increased proinflammatory cytokines and myocardial injury were observed in mice with obesity, and silencing of LEAP-2 ameliorated HFD-induced hyperlipidemia, inflammation, and myocardial injury. Moreover, HFD-induced macrophage infiltration and M1 polarization were reversed by LEAP-2 knockdown in mice. Furthermore, silencing of LEAP-2 suppressed PA-induced M1 polarization but enhanced M2 polarization in vitro. LEAP-2 interacted with GHSR in macrophages, and knockdown of LEAP-2 promoted the interaction of GHSR and ghrelin. Overexpression of ghrelin enhanced LEAP-1 silencing-mediated suppression of inflammatory response and upregulation of M2 polarization in PA-induced macrophages. CONCLUSION: Knockdown of LEAP-2 ameliorates obesity-induced myocardial injury via promoting M2 polarization.

Ghrelin Relieves Obesity-Induced Myocardial Injury by Regulating the Epigenetic Suppression of miR-196b Mediated by lncRNA HOTAIR.

INTRODUCTION: Obesity has been believed to be closely linked with many kinds of diseases including atherosclerosis, hypertension, cerebrovascular thrombosis, and diabetes. Ghrelin and Homeobox transcript antisense RNA (HOTAIR) were believed to be involved in the regulation of myocardial injury. METHODS: The obesity mice model was established through feeding mice (C57BL/6J, male, eight-week-old) with high-fat diet and palmitate (PA)-induced cardiomyocyte injury. RNA and protein levels were detected with Quantitative real-time PCR and Western blotting. The levels of TG, TCH, LDL, CK-MB, cTnl, and BNP in the serum or cell medium supernatant were measured using ELISA kits. The ROS level was detected with the DCFH-DA method. Binding sites between different targets were identified using detection of dual luciferase reporter assay. Cell apoptosis was analyzed by flow cytometry. RNA-binding protein immunoprecipitation and chromatin immunoprecipitation were used to detect the binding of DNMT3B with HOTAIR or miR-196b promoter. RESULTS: The expression of HOTAIR was downregulated, and miR-196b was upregulated in the obese myocardial injury. Ghrelin attenuated PA-induced cardiomyocyte injury by increasing HOTAIR. HOTAIR regulated the expression of miR-196b by recruiting DNMT3B to induce methylation of the miR-196b gene promoter. The binding site between miR-196b and IGF-1 was identified. DISCUSSION/CONCLUSION: We demonstrated that ghrelin attenuated PA-induced cardiomyocyte injury by regulating the HOTAIR/miR-196b/IGF-1 signaling pathway. Our findings might provide novel thought for the prevention and treatment of obesity-induced myocardial injury by targeting HOTAIR/miR-196b.

Anatase and Rutile TiO2 Nanoparticles Lead Effective Bone Damage in Young Rat Model via the IGF-1 Signaling Pathway.

PURPOSE: To evaluate the effects of anatase and rutile TiO2 nanoparticles (NPs) on the growth and development of bones in young rats and explore their possible mechanisms. METHODS: Three-week-old male rats were orally administered anatase TiO2 NPs and rutile TiO2 NPs for 28 days. The indicators of rat growth and development, liver function, bone metabolism, and insulin-like growth factor-1 (IGF-1) levels were evaluated. Micro-computed tomography (micro-CT) and immunohistochemistry were used to evaluate the tibia. RESULTS: No significant differences were observed among growth and development indicators in young rats. Significant differences were found in IGF-1 levels, phosphorus levels, and liver function. Micro-CT revealed osteoporosis in the bones. The micro-CT data supported the same result. Bone immunohistochemistry results showed that the expression of osteoprotegerin (OPG) was decreased and the expression of receptor activator of nuclear factor-κB ligand (RANKL) and cathepsin K (CTSK) was increased. CONCLUSION: This study demonstrated that TiO2 NPs can damage bones via the IGF-1/OPG/RANKL/CTSK pathway in young rats. Furthermore, rutile TiO2 NPs damaged the bones more seriously than anatase TiO2 NPs.