β2-Adrenergic receptor (β2-AR) agonist formoterol suppresses differentiation of L6 myogenic cells by blocking PI3K-AKT pathway

Primary myoblasts from intrauterine growth-restricted fetal sheep exhibit intrinsic dysfunction of proliferation and differentiation that coincides with enrichment of inflammatory cytokine signaling pathways

Intrauterine growth restriction (IUGR) is linked to lifelong reductions in muscle mass due to intrinsic functional deficits in myoblasts, but the mechanisms underlying these deficits are not known. Our objective was to determine if the deficits were associated with changes in inflammatory and adrenergic regulation of IUGR myoblasts, as was previously observed in IUGR muscle. Primary myoblasts were isolated from IUGR fetal sheep produced by hyperthermia-induced placental insufficiency (PI-IUGR; n = 9) and their controls (n = 9) and from IUGR fetal sheep produced by maternofetal inflammation (MI-IUGR; n = 6) and their controls (n = 7). Proliferation rates were less (P < 0.05) for PI-IUGR myoblasts than their controls and were not affected by incubation with IL-6, TNF-α, norepinephrine, or insulin. IκB kinase inhibition reduced (P < 0.05) proliferation of control myoblasts modestly in basal media but substantially in TNF-α-added media and reduced (P < 0.05) PI-IUGR myoblast proliferation substantially in basal and TNF-α-added media. Proliferation was greater (P < 0.05) for MI-IUGR myoblasts than their controls and was not affected by incubation with TNF-α. Insulin increased (P < 0.05) proliferation in both MI-IUGR and control myoblasts. After 72-h differentiation, fewer (P < 0.05) PI-IUGR myoblasts were myogenin+ than controls in basal and IL-6 added media but not TNF-α-added media. Fewer (P < 0.05) PI-IUGR myoblasts were desmin+ than controls in basal media only. Incubation with norepinephrine did not affect myogenin+ or desmin+ percentages, but insulin increased (P < 0.05) both markers in control and PI-IUGR myoblasts. After 96-h differentiation, fewer (P < 0.05) MI-IUGR myoblasts were myogenin+ and desmin+ than controls regardless of media, although TNF-α reduced (P < 0.05) desmin+ myoblasts for both groups. Differentiated PI-IUGR myoblasts had greater (P < 0.05) TNFR1, ULK2, and TNF-α-stimulated TLR4 gene expression, and PI-IUGR semitendinosus muscle had greater (P < 0.05) TNFR1 and IL6 gene expression, greater (P < 0.05) c-Fos protein, and less (P < 0.05) IκBα protein. Differentiated MI-IUGR myoblasts had greater (P < 0.05) TNFR1 and IL6R gene expression, tended to have greater (P = 0.07) ULK2 gene expression, and had greater (P < 0.05) β-catenin protein and TNF-α-stimulated phosphorylation of NFκB. We conclude that these enriched components of TNF-α/TNFR1/NFκB and other inflammatory pathways in IUGR myoblasts contribute to their dysfunction and help explain impaired muscle growth in the IUGR fetus.

Curcumin alleviates rheumatoid arthritis progression through the phosphatidylinositol 3-kinase/protein kinase B pathway: an in vitro and in vivo study

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease characterized by synovial inflammation and joint bone and cartilage destruction. Curcumin can improve joint inflammation in rats with arthritis and inhibit synovial revascularization and abnormal proliferation of fibroblasts. However, it is unclear whether curcumin affects the RA progression. The TNF-α-stimulated primary RA fibroblast-like synoviocytes (RA-FLS) and SV-40 transformed MH7A cells were used as the in vitro model of RA. A mouse model of collagen-induced arthritis (CIA) was used as the in vivo model. The effects of curcumin on cell proliferation, apoptosis, migration, invasion, and inflammatory response were assessed by colony formation, flow cytometry, wound scratch, Transwell assays, and western blotting analysis. Arthritis index scores and degree of paw swelling in mice were assessed to evaluate RA. Curcumin inhibited the TNF-α-induced proliferation, migration, invasion of MH7A and RA-FLS cells and promoted cell apoptosis. Administration with curcumin reversed the CIA-induced increase in arthritis scores, hind paw edema, and loss of appetite, while these effects were rescued by insulin-like growth factor 1, the upstream cytokine of PI3K/AKT. Moreover, curcumin suppressed the inflammatory response by reducing TNF-α, IL-6, and IL-17 secretion in CIA-stimulated mice. Curcumin has an excellent anti-RA effect in vivo and in vitro, which is exerted by inhibiting the expression of pro-inflammatory factors TNF-a, IL-6 and IL-17 and inhibiting the activation of PI3K/AKT signaling pathway. Thus, curcumin may be a promising candidate for anti-RA treatment.

Yin Yang 1 is required for PHD finger protein 20-mediated myogenic differentiation in vitro and in vivo

The development of skeletal muscle requires progression of a highly ordered cascade of events comprising myogenic lineage commitment, myoblast proliferation, and terminal differentiation. The process of myogenesis is controlled by several myogenic transcription factors that act as terminal effectors of signaling cascades and produce appropriate developmental stage-specific transcripts. PHD finger protein 20 (PHF20) is a multidomain protein and subunit of a lysine acetyltransferase complex that acetylates histone H4 and p53, but its function is unclear. Notably, it has been reported that PHF20 knockout mice die shortly after birth and display a wide variety of phenotypes within the skeletal and hematopoietic systems. Therefore, the putative role of PHF20 in myogenic differentiation was further investigated. In the present study, we found that protein and mRNA expression levels of PHF20 were decreased during myogenic differentiation in C₂C₁₂ cells. At the same time, Yin Yang 1 (YY1) was also decreased during myogenic differentiation. PHF20 overexpression increased YY1 expression during myogenic differentiation, together with a delay in MyoD expression. PHF20 expression enhanced the transcriptional activity of YY1 while shRNA-mediated depletion of PHF20 resulted in the reduction of YY1 promoter activity in C₂C₁₂ cells. In addition, PHF20 directly bounds to the YY1 promoter in C₂C₁₂ cells. In a similar manner, YY1 expression was elevated while myosin heavy chain expression was decreased in PHF20 transgenic (TG) mice. Histological analysis revealed abnormalities in the shape and length of muscles in PHF20-TG mice. Furthermore, PHF20-TG muscles slowly regenerated after cardiotoxin injection, indicating that PHF20 affected muscle differentiation and regeneration after injury in vivo. Taken together, these results suggested that PHF20 plays an important role in myogenic differentiation by regulating YY1.

K-3-Rh Protects Against Cerebral Ischemia/Reperfusion Injury by Anti-Apoptotic Effect Through PI3K-Akt Signaling Pathway in Rat

BACKGROUND/AIMS

Ischemic stroke is the main cause of nerve damage and brain dysfunction, accompanied by strong brain cell apoptosis. This study aimed to investigate the effect of kaempferol-3-O-rhamnoside (K-3-rh) on cerebral ischemia-reperfusion (I/R) injury.

METHODS AND MATERIALS

A rat model of cerebral I/R injury was established. The effects of K-3-rh on cerebral infarction size, brain water content and neurological deficits in rats were evaluated. Apoptosis of ischemic brain cells after mouse I/R was observed by TUNEL staining and flow cytometry. Western blot and qRT-PCR were used to detect the effect of K-3-rh on the expression of apoptosis-related proteins.

RESULTS

K-3-rh can improve the neurological deficit score, reduce the infarct volume and brain water content, and inhibit cell apoptosis. In addition, K-3-rh significantly downregulated the expression of Bax and p53 and upregulated the expression of Bcl-2, and the phosphorylation level of Akt. Blockade of PI3K activity by the PI3K inhibitor wortmannin not only reversed the effects of K-3-rh on infarct volume and brain water content but also reversed the expression level of p-Akt.

CONCLUSION

K-3-rh had obvious neuroprotective effects on brain I/R injury and neuronal apoptosis, and its mechanism may be related to activation of PI3K/Akt signaling pathway.