phenanthrenes and Muscular-Atrophy

Triptolide is an active ingredient isolated from an ancient Chinese herb (Tripterygium wilfordii Hook. f) for inflammatory and immune disorders. It has been shown to inhibit the proliferation of skeletal muscle; however, mechanisms of this effect remain unclear. We used mouse C2C12 myotubes as an in vitro model to investigate the effects of triptolide on skeletal muscle. Triptolide markedly inhibited the expression of myosin heavy chain and upregulated the expression of muscle atrophy-related proteins, leading to atrophy of the myotubes. Triptolide dose-dependently decreased the phosphorylation of Forkhead box O3 (FoxO3) and activated FoxO3 transcription activity, which regulates the expression of muscle atrophy-related proteins. Furthermore, triptolide inhibited the phosphorylation of Akt on the site of S473 and T308, and decreased the phosphorylation of insulin receptor substrate-1 (IRS-1) on the site of S302. In addition, triptolide reduced the protein level, but not mRNA level of IRS-1, whereas other upstream regulators of the Akt signaling pathway were not affected. Finally, a time-course experiment showed that the triptolide-induced degradation of IRS-1 in myotubes occurred 12 h prior to both inhibition of Akt activity and the activation of FoxO3. These data indicate that triptolide triggers IRS-1 degradation to promote FoxO3 activation, which subsequently led to atrophy of myotubes, providing us a potential target to prevent triptolide-induced skeletal muscle atrophy.

Topics: Animals; Cell Line; Diterpenes; Epoxy Compounds; Forkhead Box Protein O3; Insulin Receptor Substrate Proteins; Mice; Muscle Fibers, Skeletal; Muscular Atrophy; Phenanthrenes; Signal Transduction

Salvia miltiorrhiza bunge (Danshen) has been extensively used to treat a wide variety of diseases including cancers. Cryptotanshinone is a major lipophilic compound extracted from the root of Danshen and has been reported to exert various pharmacological effects, however, its anti-cachectic remains unknown.. The present study aims to investigate the anti-cachectic efficacy of cryptotanshinone and elucidate the underlying mechanism.. Prevention of muscle wasting by cryptotanshinone in colon adenocarcinoma CT26-induced cachexia and CT26 conditioned medium (TCM)-induced myotubes were investigated. Main features of cancer cachexia were determined after cryptotanshinone administration. The therapeutic effect of cryptotanshinone on myotube atrophy was assessed by morphological observation and myotube fiber width determination. E3 ubiquitin ligases muscle RING-finger containing protein 1 (MuRF1) and muscle atrophy Fbox protein (MAFbx/Atrogin-1) expression and STAT3 activation were examined using western blot, real-time qPCR and dual-luciferase reporter gene assays both in vitro and in vivo. The myotubes were infected with lentiviruses expressing STAT3 or GFP.. In CT26 tumor-bearing mice, cryptotanshinone (20 and 60 mg/kg) administration drastically prevented systemic cancer cachexia from whole body weight loss and wasting of multiple tissues including heart, fat and skeletal muscle, with a negligible effect on cancer growth at dose of 20 mg/kg cryptotanshinone administration prevented the induction of MuRF1 and MAFbx/Atrogin-1 in cachectic muscles. Moreover, cryptotanshinone (2.5-10 μM) dose-dependently reduced the elevated expression of MuRF1 and MAFbx/Atrogin-1 in C2C12 myotubes, and improved myotube atrophy. We showed that cryptotanshinone significantly suppressed the hyper-activated STAT3 in cachectic muscles and C2C12 myotubes and inhibited STAT3 transcriptional activity, but it did not repress the activation of STAT1. The inhibitory effect of cryptotanshinone on TCM-induced myotube atrophy was blocked by STAT3 overexpression.. These data suggest that cryptotanshinone prevents muscle wasting in cancer cachexia through STAT3 inhibition, and it may be a promising candidate drug for the treatment of cancer cachexia.

Topics: Adenocarcinoma; Animals; Cachexia; Colonic Neoplasms; HEK293 Cells; HeLa Cells; Humans; Male; Mice, Inbred BALB C; Muscle Fibers, Skeletal; Muscle Proteins; Muscular Atrophy; Phenanthrenes; Phosphorylation; Signal Transduction; SKP Cullin F-Box Protein Ligases; STAT3 Transcription Factor; Tripartite Motif Proteins; Ubiquitin-Protein Ligases; Weight Loss

Insulin resistance causes type 2 diabetes; therefore, increasing insulin sensitivity is a therapeutic approach against type 2 diabetes. Activating AMP-activated protein kinase (AMPK) is an effective approach for treating diabetes, and reduced insulin receptor substrate-1 (IRS-1) protein levels have been suggested as a molecular mechanism causing insulin resistance. Thus, dual targeting of AMPK and IRS-1 might provide an ideal way to treat diabetes. We found that 15,16-dihydrotanshinone I (DHTS), as a C1-Ten protein tyrosine phosphatase inhibitor, increased IRS-1 stability, improved glucose tolerance and reduced muscle atrophy. Identification of DHTS as a C1-Ten inhibitor revealed a new function of C1-Ten in AMPK inhibition, possibly through regulation of IRS-1. These findings suggest that C1-Ten inhibition by DHTS could provide a novel therapeutic strategy for insulin resistance-associated metabolic syndrome through dual targeting of IRS-1 and AMPK.

Topics: AMP-Activated Protein Kinases; Animals; Cell Line; Enzyme Activation; Furans; Glucose; Glucose Tolerance Test; Humans; Hypoglycemic Agents; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Male; Metabolic Syndrome; Mice; Mice, Inbred C57BL; Muscle, Skeletal; Muscular Atrophy; Phenanthrenes; Protein Tyrosine Phosphatases; Quinones; Signal Transduction