Catalpol prevents denervated muscular atrophy related to the inhibition of autophagy and reduces BAX/BCL2 ratio via mTOR pathway

A study on the mechanism of Beclin-1 m6A modification mediated by catalpol in protection against neuronal injury and autophagy following cerebral ischemia

OBJECTIVE

Catalpol (CAT) has various pharmacological activities and plays a protective role in cerebral ischemia. It has been reported that CAT played a protective role in cerebral ischemia by upregulaing NRF1 expression. Bioinformatics analysis reveals that NRF1 can be used as a transcription factor to bind to the histone acetyltransferase KAT2A. However, the role of KAT2A in cerebral ischemia remains to be studied. Therefore, we aimed to investigate the role of CAT in cerebral ischemia and its related mechanism.

METHODS

In vitro, a cell model of oxygen and glucose deprivation/reperfusion (OGD/R) was constructed, followed by evaluation of neuronal injury and the expression of METTL3, Beclin-1, NRF1, and KAT2A. In vivo, a MCAO rat model was prepared by means of focal cerebral ischemia, followed by assessment of neurological deficit and brain injury in MCAO rats. Neuronal autophagy was evaluated by observation of autophagosomes in neurons or brain tissues by TEM and detection of the expression of LC3 and p62.

RESULTS

In vivo, CAT reduced the neurological function deficit and infarct volume, inhibited neuronal apoptosis in the cerebral cortex, and significantly improved neuronal injury and excessive autophagy in MCAO rats. In vitro, CAT restored OGD/R-inhibited cell viability, inhibited cell apoptosis, LDH release, and neuronal autophagy. Mechanistically, CAT upregulated NRF1, NRF1 activated METTL3 via KAT2A transcription, and METTL3 inhibited Beclin-1 via m6A modification.

CONCLUSION

CAT activated the NRF1/KAT2A/METTL3 axis and downregulated Beclin-1 expression, thus relieving neuronal injury and excessive autophagy after cerebral ischemia.

Spinal Muscular Atrophy Treatment: The MTOR Regulatory Intervention

Spinal muscular atrophy (SMA) is a hereditary disorder affecting neurons and muscles, resulting in muscle weakness and atrophy. Most SMA cases are diagnosed during infancy or early childhood, the most common inherited cause of infant mortality without treatment. Still, SMA might appear at older ages with milder symptoms. SMA patients demonstrate progressive muscle waste, movement problems, tremors, dysphagia, bone and joint deformations, and breathing difficulties. The mammalian target of rapamycin (mTOR), the mechanistic target of rapamycin, is a member of the phosphatidylinositol 3-kinase-related kinase family of protein kinases encoded by the mTOR gene in humans. The mTOR phosphorylation, deregulation, and autophagy have shown dissimilarity amongst SMA cell types. Therefore, exploring the underlying molecular process in SMA therapy could provide novel insights and pave the way for finding new treatment options. This paper provides new insight into the possible modulatory effect of mTOR/ autophagy in SMA management.

Catalpol Inhibits Autophagy to Ameliorate Doxorubicin-Induced Cardiotoxicity via the AKT-mTOR Pathway

As a kind of anthracycline, doxorubicin (DOX) is commonly used as an antitumor drug, but its clinical application has been greatly hindered due to its severe cardiotoxicity. Hence, in this study, we investigated the role of catalpol (CTP) and its effect on DOX-induced cardiotoxicity.The cardiac function of mice was evaluated by assessing lactate dehydrogenase, creatine kinase isoenzyme, heart weight to body weight, and heart weight/tibia length levels. Histopathological changes were observed using hematoxylin and eosin staining, and the terminal deoxynucleotidyl transferase dUTP nick end labeling assay was used to examine myocardial apoptosis. Superoxide dismutase (SOD) activity, glutathione (GSH), and malondialdehyde (MDA) levels were measured to confirm the changes in oxidative stress. Western blotting showed the levels of autophagy- and pathway-related proteins. Expression of autophagy marker LC3 was examined using immunofluorescence staining.CTP alleviated DOX-induced cardiac damage in mice. We further observed upregulated SOD and GSH levels, and downregulated MDA level after the CTP treatment in DOX-treated mice, indicating the protective role of CTP against oxidative injury. DOX-induced myocardial apoptosis was also inhibited by CTP treatment in mice. In addition, CTP decreased the levels of Beclin1 and LC3II/LC3I, increased the levels of P62, and activated the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway in DOX-treated mice.CTP ameliorated DOX-induced cardiotoxicity by inhibiting oxidative stress, myocardial apoptosis, and autophagy via the AKT-mTOR pathway.

Cancer-derived exosome miRNAs induce skeletal muscle wasting by Bcl-2-mediated apoptosis in colon cancer cachexia

Cancer cachexia is a kind of whole-body metabolic disorder syndrome accompanied by severe wasting of muscle tissue in which cancer exosomes may be involved. Analysis of clinical samples showed that the serum exosome concentrations were correlated with the development of cancer cachexia. Exosomes secreted by C26 cells could decrease the diameter of C2C12 myotubes in vitro and decrease mouse muscle strength and tibialis anterior (TA) muscle weight in vivo. GW4869, an inhibitor of exosome excretion, ameliorated muscle wasting in C26 tumor-bearing mice. MicroRNA (miRNA) sequencing (miRNA-seq) analysis suggested that miR-195a-5p and miR-125b-1-3p were richer in C26 exosomes than in exosomes secreted from MC38 cells (non-cachexic). Both miR-195a-5p and miR-125b-1-3p mimics could induce atrophy of C2C12 myoblasts. Downregulation of Bcl-2 and activation of the apoptotic signaling pathway were observed in C2C12 myoblasts transfected with miR-195a-5p and miR-125b-1-3p mimics, in the gastrocnemius muscle of C26 tumor-bearing mice and in the TA muscle injected with C26 exosomes. Results of dual-luciferase assay confirmed the targeting of miR-195a-5p/miR-125b-1-3p to Bcl-2. Overexpression of Bcl-2 successfully reversed atrophy of C2C12 myoblasts induced by the two miRNA mimics. These results suggested that cancer exosome enriched miRNAs might induce muscle atrophy by targeting Bcl-2-mediated apoptosis.

A potential therapeutic effect of catalpol in Duchenne muscular dystrophy revealed by binding with TAK1

BACKGROUND

Duchenne muscular dystrophy (DMD) is a progressive muscle disease caused by the loss of dystrophin, which results in inflammation, fibrosis, and the inhibition of myoblast differentiation in skeletal muscle. Catalpol, an iridoid glycoside, improves skeletal muscle function by enhancing myogenesis; it has potential to treat DMD. We demonstrate the positive effects of catalpol in dystrophic skeletal muscle.

METHODS

mdx (loss of dystrophin) mice (n = 18 per group) were treated with catalpol (200 mg/kg) for six consecutive weeks. Serum analysis, skeletal muscle performance and histology, muscle contractile function, and gene and protein expression were performed. Molecular docking and ligand-target interactions, RNA interference, immunofluorescence, and plasmids transfection were utilized to explore the protective mechanism in DMD by which catalpol binding with transforming growth factor-β-activated kinase 1 (TAK1) in skeletal muscle.

RESULTS

Six weeks of catalpol treatment improved whole-body muscle health in mdx mice, which was characterized by reduced plasma creatine kinase (n = 18, -35.1%, P < 0.05) and lactic dehydrogenase (n = 18, -10.3%, P < 0.05) activity. These effects were accompanied by enhanced grip strength (n = 18, +25.4%, P < 0.05) and reduced fibrosis (n = 18, -29.0% for hydroxyproline content, P < 0.05). Moreover, catalpol treatment protected against muscle fatigue and promoted muscle recovery in the tibialis anterior (TA) and diaphragm (DIA) muscles (n = 6, +69.8%, P < 0.05 and + 74.8%, P < 0.001, respectively), which was accompanied by enhanced differentiation in primary myoblasts from DMD patients (n = 6, male, mean age: 4.7 ± 1.9 years) and mdx mice. In addition, catalpol eliminated p-TAK1 overexpression in mdx mice (n = 12, -21.3%, P < 0.05) and primary myoblasts. The catalpol-induced reduction in fibrosis and increased myoblast differentiation resulted from the inhibition of TAK1 phosphorylation, leading to reduced myoblast trans-differentiation into myofibroblasts. Catalpol inhibited the phosphorylation of TAK1 by binding to TAK1, possibly at Asp-206, Thr-208, Asn-211, Glu-297, Lys-294, and Tyr-293.

CONCLUSIONS

Our findings show that catalpol and TAK1 inhibitors substantially improve whole-body muscle health and the function of dystrophic skeletal muscles and may provide a novel therapy for DMD.

Isoquercitrin Delays Denervated Soleus Muscle Atrophy by Inhibiting Oxidative Stress and Inflammation

Although denervated muscle atrophy is common, the underlying molecular mechanism remains unelucidated. We have previously found that oxidative stress and inflammatory response may be early events that trigger denervated muscle atrophy. Isoquercitrin is a biologically active flavonoid with antioxidative and anti-inflammatory properties. The present study investigated the effect of isoquercitrin on denervated soleus muscle atrophy and its possible molecular mechanisms. We found that isoquercitrin was effective in alleviating soleus muscle mass loss following denervation in a dose-dependent manner. Isoquercitrin demonstrated the optimal protective effect at 20 mg/kg/d, which was the dose used in subsequent experiments. To further explore the protective effect of isoquercitrin on denervated soleus muscle atrophy, we analyzed muscle proteolysis via the ubiquitin-proteasome pathway, mitophagy, and muscle fiber type conversion. Isoquercitrin significantly inhibited the denervation-induced overexpression of two muscle-specific ubiquitin ligases—muscle RING finger 1 (MuRF1) and muscle atrophy F-box (MAFbx), and reduced the degradation of myosin heavy chains (MyHCs) in the target muscle. Following isoquercitrin treatment, mitochondrial vacuolation and autophagy were inhibited, as evidenced by reduced level of autophagy-related proteins (ATG7, BNIP3, LC3B, and PINK1); slow-to-fast fiber type conversion in the target muscle was delayed via triggering expression of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α); and the production of reactive oxygen species (ROS) in the target muscle was reduced, which might be associated with the upregulation of antioxidant factors (SOD1, SOD2, NRF2, NQO1, and HO1) and the downregulation of ROS production-related factors (Nox2, Nox4, and DUOX1). Furthermore, isoquercitrin treatment reduced the levels of inflammatory factors—interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α)—in the target muscle and inactivated the JAK/STAT3 signaling pathway. Overall, isoquercitrin may alleviate soleus muscle atrophy and mitophagy and reverse the slow-to-fast fiber type conversion following denervation via inhibition of oxidative stress and inflammatory response. Our study findings enrich the knowledge regarding the molecular regulatory mechanisms of denervated muscle atrophy and provide a scientific basis for isoquercitrin as a protective drug for the prevention and treatment of denervated muscle atrophy.

S-allyl cysteine: A potential compound against skeletal muscle atrophy

BACKGROUND

Oxidative stress is crucial player in skeletal muscle atrophy pathogenesis. S-allyl cysteine (SAC), an organosulfur compound of Allium sativum, possesses broad-spectrum properties including immuno- and redox-modulatory impact. Considering the role of SAC in regulating redox balance, we hypothesize that SAC may have a protective role in oxidative-stress induced atrophy.

METHODS

C2C12 myotubes were treated with H₂O₂ (100 μM) in the presence or absence of SAC (200 μM) to study morphology, redox status, inflammatory cytokines and proteolytic systems using fluorescence microscopy, biochemical analysis, real-time PCR and immunoblotting approaches. The anti-atrophic potential of SAC was confirmed in denervation-induced atrophy model.

RESULTS

SAC pre-incubation (4 h) could protect the myotube morphology (i.e. length/diameter/fusion index) from atrophic effects of H₂O₂. Lower levels of ROS, lipid peroxidation, oxidized glutathione and altered antioxidant enzymes were observed in H₂O₂-exposed cells upon pre-treatment with SAC. SAC supplementation also suppressed the rise in cytokines levels (TWEAK/IL6/myostatin) caused by H₂O₂. SAC treatment also moderated the degradation of muscle-specific proteins (MHCf) in the H₂O₂-treated myotubes supported by lower induction of diverse proteolytic systems (i.e. cathepsin, calpain, ubiquitin-proteasome E3-ligases, caspase-3, autophagy). Denervation-induced atrophy in mice illustrates that SAC administration alleviates the negative effects (i.e. mass loss, decreased cross-sectional area, up-regulation of proteolytic systems, and degradation of total/specific protein) of denervation on muscles.

CONCLUSIONS

SAC exerts significant anti-atrophic effects to protect myotubes from H₂O₂-induced protein loss and myofibers from denervation-induced muscle loss, due to the prevention of elevated proteolytic systems and inflammatory/oxidative molecules.

GENERAL SIGNIFICANCE

The results signify the potential of SAC against muscle atrophy.

Catalpol‑mediated microRNA‑34a suppresses autophagy and malignancy by regulating SIRT1 in colorectal cancer

Colorectal cancer (CRC) is one of the most common digestive tract tumors worldwide. Catalpol exerts inhibitory effects on the progression of several cancer types by regulating microRNAs (miRs). However, the precise role and carcinostatic mechanism of catalpol on CRC cells are poorly understood which limits the application of catalpol treatment. In the present study, miR-34a and sirtuin 1 (SIRT1) expression levels were detected in CRC tissues and CRC cell lines by RT-qPCR. Computational software analysis, luciferase assays and western blotting were used to demonstrate the downstream target of miR-34a in CRC cells. Effects of catalpol on cell viability, apoptosis, autophagic flux and the miR-34a/SIRT1 axis in the CRC cells were assessed by CCK-8 assay, flow cytometry, electron microscopy and western blotting, respectively. Whether the miR-34a/SIRT1 axis participated in catalpol-mediated autophagy and apoptosis was investigated. The effects of catalpol on the miR-34a/SIRT1 axis and malignant behavior were evaluated in a rat model of azoxymethane (AOM)-induced CRC. It was revealed that miR-34a expression levels were significantly decreased while SIRT1 was overexpressed in most of the CRC tissues and all the CRC cell lines. Clinically, a low level of miR-34a was correlated with poor clinicopathological characteristics in CRC patients. Catalpol reduced cell viability, suppressed autophagy, promoted apoptosis, and regulated the expression of SIRT1 by inducing miR-34a in vitro and in vivo. The autophagy-inhibiting effect of catalpol may be a mechanism to promote apoptosis of CRC cells. miR-34a mimic transfection resulted in autophagy-suppressive activity similar to that of catalpol, while the miR-34a inhibitor attenuated the antiautophagic effects of catalpol. In conclusion, miR-34a is involved in regulating catalpol-mediated autophagy and malignant behavior by directly inhibiting SIRT1 in CRC.

Monoterpenes modulating autophagy: A review study

From the beginning of the 21st century, much attention has been made towards the medicinal herbs due to their low side effects and valuable biological activities. Among them, terpenes comprise a large group of naturally occurring chemical compounds that are considered as main components of flavours, antifeedants and pheromones. Monoterpenes have demonstrated a favourable profile as compounds that have antioxidant, anti-inflammatory, anti-diabetic, hepatoprotective and anti-tumour activities. On the other hand, autophagy is a 'self-digestion' mechanism which plays a remarkable role in a number of pathological conditions such as cancer, ageing, metabolic disorders and infection. Also, autophagy is considered as a stress adaptor that may lead to apoptotic cell death under severe and sustained stress. Autophagy modulation is a promising strategy in cancer treatment, and a variety of drugs have been designed in line with this strategy. In the present MiniReview, we discuss the effects of monoterpenes on autophagy and its relationship with therapeutic impacts of monoterpenes.

The protective effect and mechanism of catalpol on high glucose-induced podocyte injury

BACKGROUND

Catalpol, a natural iridoid glycoside in Rehmannia glutinosa, can alleviate proteinuria associated with diabetic nephropathy (DN), however, whether catalpol has a protective effect against podocyte injury in DN remains unclear.

METHODS

In this study, we used a high glucose (HG)-induced podocyte injury model to evaluate the protective effect and mechanism of catalpol against HG-induced podocyte injury. Cell viability was determined by the 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. The levels of lactate dehydrogenase (LDH), superoxide dismutase (SOD) and malondialdehyde (MDA) were measured by commercial assay kits. Cell apoptosis and reactive oxygen species (ROS) were determined by using flow cytometry. Tumour necrosis factor α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) levels were determined by enzyme-linked immunosorbent assay (ELISA). The protein expression levels of B-cell lymphoma-2 (Bcl-2), Bcl2-associated x (Bax), cleaved caspase-3, nicotinamide adenine dinucleotide phosphate oxidase enzyme 4 (NOX4), toll-like receptor 4 (TLR4), myeloid differentiation primary response gene 88 (MyD88), p38 mitogen-activated protein kinase (p38 MAPK), phosphorylated p38 MAPK (p-p38 MAPK), nuclear factor kappa B inhibitor alpha (IκBα) and phosphorylated IκBα (p-IκBα) were measured by western blotting. In addition, Bcl-2, Bax, caspase-3 and nuclear factor kappa B (NF-κB) levels were determined by immunofluorescence staining.

RESULTS

Catalpol significantly increased cell viability and decreased LDH release in HG-induced podocyte injury. Catalpol significantly decreased ROS generation, apoptosis, level of MDA, levels of inflammatory cytokine TNF-α, IL-1β, and IL-6 and increased SOD activity in HG-induced podocyte injury. Moreover, catalpol significantly decreased expression of cleaved caspase-3, Bax, NOX4, TLR4, MyD88, p-p38 MAPK, p-IκBα and NF-κB nuclear translocation, as well as increased Bcl-2 expression in HG-induced podocyte injury.

CONCLUSION

Catalpol can protect against podocyte injury by ameliorating apoptosis and inflammation. These protective effects may be attributed to the inhibition of NOX4, which alleviates ROS generation and suppression of the TLR4/MyD88 and p38 MAPK signaling pathways to prevent NF-κB activation. Therefore, catalpol could be a promising drug for the prevention of DN.