ACE activity affects myogenic differentiation via mTOR signaling

Monascus pigment prevent the oxidative cytotoxicity in myotube derived hydrogen peroxide

The amounts of Reactive oxygen species (ROS) become higher by strenuous exercises which consume larger amounts of oxygen in active muscles. Since these ROS directly injured muscles, the high ROS concentration involves muscle fatigue. Thus, an immediate ROS scavenging system in the muscle is desired. Since Monascus pigment (MP) involves physiologically active substances which scavenge ROS, it may be a clue to save the muscle injury. However, there are no reports examining MP effects on oxidative stress in skeletal muscle. In this study, we investigated the effect and mechanism of MP on skeletal muscle cells damaged by oxidative stress. The ability to directly eliminate ROS was evaluated by mixing MP solutions with •OH and O2 •-, a type of ROS. The effect of peroxidation in C2C12 cells was evaluated by cell viability assay and Western blotting. MP scavenges •OH and O2 •-. MP treatment increases the survival rate under oxidative stress. At that time, the expression of catalase was increased: the enzyme change H2O2 into H2O to rescue the cells under oxidative stress. We conclude that monascus pigment suppressed myotube damage under oxidative stress by both non-enzymatic ROS scavenging and up-regulation of catalase expression.

Involvement of the Renin-Angiotensin System in Stress: State of the Art and Research Perspectives

BACKGROUND

Along with other canonical systems, the renin-angiotensin system (RAS) has shown important roles in stress. This system is a complex regulatory proteolytic cascade composed of various enzymes, peptides, and receptors. Besides the classical (ACE/Ang II/AT1 receptor) and the counter-regulatory (ACE2/Ang-(1-7)/Mas receptor) RAS axes, evidence indicates that nonclassical components, including Ang III, Ang IV, AT₂ and AT₄, can also be involved in stress.

OBJECTIVE AND METHODS

This comprehensive review summarizes the current knowledge on the participation of RAS components in different adverse environmental stimuli stressors, including air jet stress, cage switch stress, restraint stress, chronic unpredictable stress, neonatal isolation stress, and post-traumatic stress disorder.

RESULTS AND CONCLUSION

In general, activation of the classical RAS axis potentiates stress-related cardiovascular, endocrine, and behavioral responses, while the stimulation of the counter-regulatory axis attenuates these effects. Pharmacological modulation in both axes is optimistic, offering promising perspectives for stress-related disorders treatment. In this regard, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are potential candidates already available since they block the classical axis, activate the counter-regulatory axis, and are safe and efficient drugs.

Angiotensin-Converting Enzyme Inhibitor Rapidly Ameliorates Depressive-Type Behaviors via Bradykinin-Dependent Activation of Mammalian Target of Rapamycin Complex 1

BACKGROUND

Angiotensin-converting enzyme inhibitors (ACEIs) are widely prescribed antihypertensive agents. Intriguingly, case reports and clinical trials have indicated that ACEIs, including captopril and lisinopril, may have a rapid mood-elevating effect in certain patients, but few experimental studies have investigated their value as fast-onset antidepressants.

METHODS

The present study consisted of a series of experiments using biochemical assays, immunohistochemistry, and behavioral techniques to examine the effect and mechanism of captopril on depressive-like behavior in 2 animal models, the chronic unpredictable stress model and the chronic social defeat stress model.

RESULTS

Captopril (19.5 or 39 mg/kg, intraperitoneal injection) exerted rapid antidepressant activity in mice treated under the chronic unpredictable stress model and mice treated under the chronic social defeat stress model. Pharmacokinetic analysis revealed that captopril crossed the blood-brain barrier and that lisinopril, another ACEI with better blood-brain barrier permeability, exerted a faster and longer-lasting effect at a same molar equivalent dose. This antidepressant effect seemed to be independent of the renin-angiotensin system, but dependent on the bradykinin (BK) system, since the decreased BK detected in the stressed mice could be reversed by captopril. The hypofunction of the downstream effector of BK, Cdc42 (cell division control protein 42) homolog, contributed to the stress-induced loss of dendritic spines, which was rapidly reversed by captopril via activating the mTORC1 (mammalian target of rapamycin complex 1) pathway.

CONCLUSIONS

Our findings indicate that the BK-dependent activation of mTORC1 may represent a promising mechanism underlying antidepressant pharmacology. Considering their affordability and availability, ACEIs may emerge as a novel fast-onset antidepressant, especially for patients with comorbid depression and hypertension.

Kinin-B2 Receptor Activity in Skeletal Muscle Regeneration and Myoblast Differentiation

The bioactive peptide bradykinin obtained from cleavage of precursor kininogens activates the kinin-B2 receptor functioning in induction of inflammation and vasodilatation. In addition, bradykinin participates in kidney and cardiovascular development and neuronal and muscle differentiation. Here we show that kinin-B2 receptors are expressed throughout differentiation of murine C2C12 myoblasts into myotubes. An autocrine loop between receptor activation and bradykinin secretion is suggested, since bradykinin secretion is significantly reduced in the presence of the kinin-B2 receptor antagonist HOE-140 during differentiation. Expression of skeletal muscle markers and regenerative capacity were decreased after pharmacological inhibition or genetic ablation of the B2 receptor, while its antagonism increased the number of myoblasts in culture. In summary, the present work reveals to date no functions described for the B2 receptor in muscle regeneration due to the control of proliferation and differentiation of muscle precursor cells.

Angiotensin converting enzyme inhibitors and angiotensin II receptor antagonist attenuate tumor growth via polarization of neutrophils toward an antitumor phenotype

Tumor microenvironments polarize neutrophils to protumoral phenotypes. Here, we demonstrate that the angiotensin converting enzyme inhibitors (ACEis) and angiotensin II type 1 receptor (AGTR1) antagonist attenuate tumor growth via polarization of neutrophils toward an antitumoral phenotype. The ACEis or AGTR1 antagonist enhanced hypersegmentation of human neutrophils and increased neutrophil cytotoxicity against tumor cells. This neutrophil hypersegmentation was dependent on the mTOR pathway. In a murine tumor model, ACEis and AGTR1 antagonist attenuated tumor growth and enhanced neutrophil hypersegmentation. ACEis inhibited tumor-induced polarization of neutrophils to a protumoral phenotype. Neutrophil depletion reduced the antitumor effect of ACEi. Together, these data suggest that the modulation of Ang II pathway attenuates tumor growth via polarization of neutrophils to an antitumoral phenotype.

Angiotensin II blockade: how its molecular targets may signal to mitochondria and slow aging. Coincidences with calorie restriction and mTOR inhibition

Caloric restriction (CR), renin angiotensin system blockade (RAS-bl), and rapamycin-mediated mechanistic target of rapamycin (mTOR) inhibition increase survival and retard aging across species. Previously, we have summarized CR and RAS-bl's converging effects, and the mitochondrial function changes associated with their physiological benefits. mTOR inhibition and enhanced sirtuin and KLOTHO signaling contribute to the benefits of CR in aging. mTORC1/mTORC2 complexes contribute to cell growth and metabolic regulation. Prolonged mTORC1 activation may lead to age-related disease progression; thus, rapamycin-mediated mTOR inhibition and CR may extend lifespan and retard aging through mTORC1 interference. Sirtuins by deacetylating histone and transcription-related proteins modulate signaling and survival pathways and mitochondrial functioning. CR regulates several mammalian sirtuins favoring their role in aging regulation. KLOTHO/fibroblast growth factor 23 (FGF23) contribute to control Ca(2+), phosphate, and vitamin D metabolism, and their dysregulation may participate in age-related disease. Here we review how mTOR inhibition extends lifespan, how KLOTHO functions as an aging suppressor, how sirtuins mediate longevity, how vitamin D loss may contribute to age-related disease, and how they relate to mitochondrial function. Also, we discuss how RAS-bl downregulates mTOR and upregulates KLOTHO, sirtuin, and vitamin D receptor expression, suggesting that at least some of RAS-bl benefits in aging are mediated through the modulation of mTOR, KLOTHO, and sirtuin expression and vitamin D signaling, paralleling CR actions in age retardation. Concluding, the available evidence endorses the idea that RAS-bl is among the interventions that may turn out to provide relief to the spreading issue of age-associated chronic disease.

Identification of retinoic acid in a high content screen for agents that overcome the anti-myogenic effect of TGF-beta-1

BACKGROUND

Transforming growth factor beta 1 (TGF-β1) is an inhibitor of muscle cell differentiation that is associated with fibrosis, poor regeneration and poor function in some diseases of muscle. When neutralizing antibodies to TGF-β1 or the angiotensin II inhibitor losartan were used to reduce TGF-β1 signaling, muscle morphology and function were restored in mouse models of Marfan Syndrome and muscular dystrophy. The goal of our studies was to identify additional agents that overcome the anti-myogenic effect of TGF-β1.

METHODOLOGY/PRINCIPAL FINDINGS

A high-content cell-based assay was developed in a 96-well plate format that detects the expression of myosin heavy chain (MHC) in C2C12 cells. The assay was used to quantify the dose-dependent responses of C2C12 cell differentiation to TGF-β1 and to the TGF-β1 Type 1 receptor kinase inhibitor, SB431542. Thirteen agents previously described as promoting C2C12 differentiation in the absence of TGF-β1 were screened in the presence of TGF-β1. Only all-trans retinoic acid and 9-cis retinoic acid allowed a maximal level of C2C12 cell differentiation in the presence of TGF-β1; the angiotensin-converting enzyme inhibitor captopril and 10 nM estrogen provided partial rescue. Vitamin D was a potent inhibitor of retinoic acid-induced myogenesis in the presence of TGF-β1. TGF-β1 inhibits myoblast differentiation through activation of Smad3; however, retinoic acid did not inhibit TGF-β1-induced activation of a Smad3-dependent reporter gene in C2C12 cells.

CONCLUSIONS/SIGNIFICANCE

Retinoic acid alleviated the anti-myogenic effect of TGF-β1 by a Smad3-independent mechanism. With regard to the goal of improving muscle regeneration and function in individuals with muscle disease, the identification of retinoic acid is intriguing in that some retinoids are already approved for human therapy. However, retinoids also have well-described adverse effects. The quantitative, high-content assay will be useful to screen for less-toxic retinoids or combinations of agents that promote myoblast differentiation in the presence of TGF-β1.

Skeletal muscle myoblasts possess a stretch-responsive local angiotensin signalling system

A paucity of information exists regarding the presence of local renin—angiotensin systems (RASs) in skeletal muscle and associated muscle stem cells. Skeletal muscle and muscle stem cells were isolated from C57BL/6 mice and examined for the presence of a local RAS using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), immunohistochemistry (IHC), Western blotting and liquid chromatography-mass spectrometry (LC-MS). Furthermore, the effect of mechanical stimulation on RAS member gene expression was analysed. Whole skeletal muscle, primary myoblasts and C2C12 derived myoblasts and myotubes differentially expressed members of the RAS including angiotensinogen, angiotensin-converting enzyme (ACE), angiotensin II (Ang II) type 1 (AT1) and type 2 (AT2). Renin transcripts were never detected, however, mRNA for the ‘renin-like’ enzyme cathepsin D was observed and Ang I and Ang II were identified in cell culture supernatants from proliferating myoblasts. AT1 appeared to co-localise with polymerised actin filaments in proliferating myoblasts and was primarily found in the nucleus of terminally differentiated myotubes. Furthermore, mechanical stretch of proliferating and differentiating C2C12 cells differentially induced mRNA expression of angiotensinogen, AT 1 and AT2. Proliferating and differentiated muscle stem cells possess a local stress-responsive RAS in vitro. The precise function of a local RAS in myoblasts remains unknown. However, evidence presented here suggests that Ang II may be a regulator of skeletal muscle myoblasts.