BGP-15 improves contractile function of regenerating soleus muscle

Prevention of Atrial Fibrillation: Putting Proteostasis Derailment Back on Track

Despite the many attempts to treat atrial fibrillation (AF), the most common cardiac tachyarrhythmia in the Western world, the treatment efficacy of AF is still suboptimal. A plausible reason for the suboptimal efficacy is that the current treatments are not directed at the underlying molecular mechanisms that drive AF. Recent discoveries revealed that the derailment of specific molecular proteostasis pathways drive electrical conduction disorders, contractile dysfunction and AF. The degree of this so-called 'electropathology' corresponds to the response to anti-AF treatment. Hence, to develop effective therapies to prevent AF, understanding the molecular mechanisms is of key importance. In this review, we highlight the key modulators of proteostasis derailment and describe the mechanisms that explain how they affect electrical and contractile function in atrial cardiomyocytes and AF. The key modulators of proteostasis derailment include (1) exhaustion of cardioprotective heat shock proteins (HSPs), (2) excessive endoplasmic reticulum (ER) stress and downstream autophagic protein degradation, (3) histone deacetylase 6 (HDAC6)-induced microtubule disruption, (4) activation of DNA damage-PARP1 activation and NAD⁺ axis and (5) mitochondrial dysfunction. Furthermore, we discuss druggable targets within these pathways that are involved in the prevention of proteostasis derailment, as well as the targets that aid in the recovery from AF. Finally, we will elaborate on the most favorable druggable targets for (future) testing in patients with AF, as well as drugs with potential benefits for AF recovery.

Glutamine supplementation accelerates functional recovery of EDL muscles after injury by modulating the expression of S100 calcium-binding proteins

The aim of the current study was to investigate the effect of glutamine supplementation on the expression of HSP70 and the calcium-binding proteins from the S100 superfamily in the recovering extensor digitorum longus (EDL) muscle after injury. Two-month-old Wistar rats were subjected to cryolesion of the EDL muscle and then randomly divided into two groups (with or without glutamine supplementation). Starting immediately after the injury, the supplemented group received daily doses of glutamine (1 g/kg/day, via gavage) for 3 and 10 days orally. Then, muscles were subjected to histological, molecular, and functional analysis. Glutamine supplementation induced an increase in myofiber size of regenerating EDL muscles and prevented the decline in maximum tetanic strength of these muscles evaluated 10 days after injury. An accelerated upregulation of myogenin mRNA levels was detected in glutamine-supplemented injured muscles on day 3 post-cryolesion. The HSP70 expression increased only in the injured group supplemented with glutamine for 3 days. The increase in mRNA levels of NF-κB, the pro-inflammatory cytokines IL-1β and TNF-α, and the calcium-binding proteins S100A8 and S100A9 on day 3 post-cryolesion in EDL muscles was attenuated by glutamine supplementation. In contrast, the decrease in S100A1 mRNA levels in the 3-day-injured EDL muscles was minimized by glutamine supplementation. Overall, our results suggest that glutamine supplementation accelerates the recovery of myofiber size and contractile function after injury by modulating the expression of myogenin, HSP70, NF-κB, pro-inflammatory cytokines, and S100 calcium-binding proteins.

The fibrotic niche impairs satellite cell function and muscle regeneration in mouse models of Marfan syndrome

AIM

It has been suggested that the proliferation and early differentiation of myoblasts are impaired in Marfan syndrome (MFS) mice during muscle regeneration. However, the underlying cellular and molecular mechanisms remain poorly understood. Here, we investigated muscle regeneration in MFS mouse models by analyzing the influence of the fibrotic niche on satellite cell function.

METHODS

In vivo, ex vivo, and in vitro experiments were performed. In addition, we evaluated the effect of the pharmacological inhibition of fibrosis using Ang-(1-7) on regenerating skeletal muscles of MFS mice.

RESULTS

The skeletal muscle of MFS mice shows an increased accumulation of collagen fibers (81.2%), number of fibroblasts (157.1%), and Smad2/3 signaling (110.5%), as well as an aberrant number of fibro-adipogenic progenitor cells in response to injury compared with wild-type mice. There was an increased number of proinflammatory and anti-inflammatory macrophages (3.6- and 3.1-fold, respectively) in regenerating muscles of wild-type mice, but not in the regenerating muscles of MFS mice. Our data show that proliferation and differentiation of satellite cells are altered (p ≤ 0.05) in MFS mice. Myoblast transplantation assay revealed that the regenerating muscles from MFS mice have reduced satellite cell self-renewal capacity (74.7%). In addition, we found that treatment with Ang-(1-7) reduces fibrosis (71.6%) and ameliorates satellite cell dysfunction (p ≤ 0.05) and muscle contractile function (p ≤ 0.05) in MFS mice.

CONCLUSION

The fibrotic niche, caused by Fbn1 mutations, reduces the myogenic potential of satellite cells, affecting structural and functional muscle regeneration. In addition, the fibrosis inhibitor Ang-(1-7) partially counteracts satellite cell abnormalities and restores myofiber size and contractile force in regenerating muscles.

Glutamine supplementation improves contractile function of regenerating soleus muscles from rats

This study evaluated the effects of glutamine supplementation immediately after freezing injury on morphological and contractile function of regenerating soleus muscles from rats. Young male Wistar rats were subjected to cryolesion of soleus muscles, and immediately after received a daily supplementation of glutamine (1 g/kg/day). The muscles were evaluated on post-injury days 3 and 10. Glutamine-supplemented injured muscles had a lower number of CD11b positive immune cells and higher mRNA levels of IL-4 compared to those from the cryolesioned muscles analyzed on post-injury day 3. The mRNA and protein expression levels of the myogenic transcription factor MyoD were also higher in glutamine-supplemented injured muscles than in injured muscles examined on post-cryolesion day 3. In addition, glutamine-supplemented injured muscles had a higher size of their regenerating myofibers, attenuated decline in maximum tetanic strength and improved fatigue resistance compared to those from injured muscles evaluated on post-cryolesion day 10. No effect was observed in uninjured muscles supplemented with glutamine. Our results suggest that glutamine supplementation improves the resolution of inflammation, as well as the size and functional recovery of regenerating myofibers from soleus muscles by accelerating the up-regulation of IL-4 and MyoD expression. Future non-pharmacological rehabilitation studies are warranted to investigate the effect of glutamine supplementation on the outcome of injured skeletal muscles.

Mitochondria-targeted therapeutics, MitoQ and BGP-15, reverse aging-associated meiotic spindle defects in mouse and human oocytes

STUDY QUESTION

Do mitochondria-targeted therapies reverse ageing- and oxidative stress-induced spindle defects in oocytes from mice and humans?

SUMMARY ANSWER

Exposure to MitoQ or BGP-15 during IVM protected against spindle and chromosomal defects in mouse oocytes exposed to oxidative stress or derived from reproductively aged mice whilst MitoQ promoted nuclear maturation and protected against chromosomal misalignments in human oocytes.

WHAT IS KNOWN ALREADY

Spindle and chromosomal abnormalities in oocytes are more prevalent with maternal aging, increasing the risk of aneuploidy, miscarriage and genetic disorders such as Down's syndrome. The origin of compromised oocyte function may be founded in mitochondrial dysfunction and increased reactive oxygen species (ROS).

STUDY DESIGN, SIZE, DURATION

Oocytes from young and old mice were treated with MitoQ and/or BGP-15 during IVM. To directly induce mitochondrial dysfunction, oocytes were treated with H2O2, and then treated the MitoQ and/or BGP-15. Immature human oocytes were cultured with or without MitoQ. Each experiment was repeated at least three times, and data were analyzed by unpaired-sample t-test or chi-square test.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Immature germinal vesicle (GV) stage oocytes from 1-, 12- and 18-month-old mice were obtained from preovulatory ovarian follicles. Oocytes were treated with MitoQ and/or BGP-15 during IVM. GV-stage human oocytes were cultured with or without MitoQ. Mitochondrial membrane potential and mitochondrial ROS were measured by live-cell imaging. Meiotic spindle and chromosome alignments were visualized by immunofluorescent labeling of fixed oocytes and the 3-dimensional images were analyzed by Imaris.

MAIN RESULTS AND THE ROLE OF CHANCE

MitoQ or BGP-15 during IVM protects against spindle and chromosomal defects in oocytes exposed to oxidative stress and in oocytes from aged mice (P < 0.001). In human oocytes, the presence of MitoQ during IVM promoted nuclear maturation and had a similar positive effect in protecting against chromosomal misalignments (P < 0.001).

LIMITATIONS, REASONS FOR CAUTION

Our study identifies two excellent candidates that may help to improve fertility in older women. However, these potential therapies must be tested for efficacy in clinical IVM systems, and undergo thorough examination of resultant offspring in preclinical models before utilization.

WIDER IMPLICATIONS OF THE FINDINGS

Our results using in-vitro systems for oocyte maturation in both mouse and human provide proof of principle that mitochondrially targeted molecules such as MitoQ and BGP-15 may represent a novel therapeutic approach against maternal aging-related spindle and chromosomal abnormalities.

STUDY FUNDING/COMPETING INTEREST(S)

The project was financially supported by the National Health and Medical Research Council and Australian Research Council, Australia. U.A.-Z. was supported by the Iraqi Higher Education and Scientific Research Ministry PhD scholarship and O.C. was supported by TUBITAK-1059B191601275. M.P.M. consults for MitoQ Inc. and holds patents in mitochondria-targeted therapies. R.L.R. is an inventor on patents relating to the use of BGP-15 to improve gamete quality.

TRIAL REGISTRATION NUMBER

N/A.

The Paradoxical Effect of PARP Inhibitor BGP-15 on Irinotecan-Induced Cachexia and Skeletal Muscle Dysfunction

Simple Summary

Both cancer and the chemotherapy used to treat it are drivers of cachexia, a life-threatening body-wasting condition which complicates cancer treatment. Poly-(ADP-ribose) polymerase (PARP) inhibitors are currently being investigated as a treatment against cancer. Here, we present paradoxical evidence that they might also be useful for mitigating the skeletal muscle specific side-effects of anti-cancer chemotherapy or exacerbate them. BGP-15 is a small molecule PARP inhibitor which protected against irinotecan (IRI)-induced cachexia and loss of skeletal muscle mass and dysfunction in our study. However, peculiarly, BGP-15 adjuvant therapy reduced protein synthesis rates and the expression of key cytoskeletal proteins associated with the dystrophin-associated protein complex and increased matrix metalloproteinase activity, while it increased the propensity for fast-twitch muscles to tear during fatiguing contraction. Our data suggest that both IRI and BGP-15 cause structural remodeling involving proteins associated with the contractile apparatus, cytoskeleton and/or the extracellular matrix which may be only transient and ultimately beneficial or may paradoxically onset a muscular dystrophy phenotype and be detrimental if more permanent.

Abstract

Chemotherapy-induced muscle wasting and dysfunction is a contributing factor to cachexia alongside cancer and increases the risk of morbidity and mortality. Here, we investigate the effects of the chemotherapeutic agent irinotecan (IRI) on skeletal muscle mass and function and whether BGP-15 (a poly-(ADP-ribose) polymerase-1 (PARP-1) inhibitor and heat shock protein co-inducer) adjuvant therapy could protect against IRI-induced skeletal myopathy. Healthy 6-week-old male Balb/C mice (n = 24; 8/group) were treated with six intraperitoneal injections of either vehicle, IRI (30 mg/kg) or BGP-15 adjuvant therapy (IRI+BGP; 15 mg/kg) over two weeks. IRI reduced lean and tibialis anterior mass, which were attenuated by IRI+BGP treatment. Remarkably, IRI reduced muscle protein synthesis, while IRI+BGP reduced protein synthesis further. These changes occurred in the absence of a change in crude markers of mammalian/mechanistic target of rapamycin (mTOR) Complex 1 (mTORC1) signaling and protein degradation. Interestingly, the cytoskeletal protein dystrophin was reduced in both IRI- and IRI+BGP-treated mice, while IRI+BGP treatment also decreased β-dystroglycan, suggesting significant remodeling of the cytoskeleton. IRI reduced absolute force production of the soleus and extensor digitorum longus (EDL) muscles, while IRI+BGP rescued absolute force production of the soleus and strongly trended to rescue force output of the EDL (p = 0.06), which was associated with improvements in mass. During the fatiguing stimulation, IRI+BGP-treated EDL muscles were somewhat susceptible to rupture at the musculotendinous junction, likely due to BGP-15’s capacity to maintain the rate of force development within a weakened environment characterized by significant structural remodeling. Our paradoxical data highlight that BGP-15 has some therapeutic advantage by attenuating IRI-induced skeletal myopathy; however, its effects on the remodeling of the cytoskeleton and extracellular matrix, which appear to make fast-twitch muscles more prone to tearing during contraction, could suggest the induction of muscular dystrophy and, thus, require further characterization.

Andersen-Tawil Syndrome Is Associated With Impaired PIP2 Regulation of the Potassium Channel Kir2.1

Andersen-Tawil syndrome (ATS) type-1 is associated with loss-of-function mutations in KCNJ2 gene. KCNJ2 encodes the tetrameric inward-rectifier potassium channel Kir2.1, important to the resting phase of the cardiac action potential. Kir-channels' activity requires interaction with the agonist phosphatidylinositol-4,5-bisphosphate (PIP₂). Two mutations were identified in ATS patients, V77E in the cytosolic N-terminal "slide helix" and M307V in the C-terminal cytoplasmic gate structure "G-loop." Current recordings in Kir2.1-expressing HEK cells showed that each of the two mutations caused Kir2.1 loss-of-function. Biotinylation and immunostaining showed that protein expression and trafficking of Kir2.1 to the plasma membrane were not affected by the mutations. To test the functional effect of the mutants in a heterozygote set, Kir2.1 dimers were prepared. Each dimer was composed of two Kir2.1 subunits joined with a flexible linker (i.e. WT-WT, WT dimer; WT-V77E and WT-M307V, mutant dimer). A tetrameric assembly of Kir2.1 is expected to include two dimers. The protein expression and the current density of WT dimer were equally reduced to ~25% of the WT monomer. Measurements from HEK cells and Xenopus oocytes showed that the expression of either WT-V77E or WT-M307V yielded currents of only about 20% compared to the WT dimer, supporting a dominant-negative effect of the mutants. Kir2.1 sensitivity to PIP₂ was examined by activating the PIP₂ specific voltage-sensitive phosphatase (VSP) that induced PIP₂ depletion during current recordings, in HEK cells and Xenopus oocytes. PIP₂ depletion induced a stronger and faster decay in Kir2.1 mutant dimers current compared to the WT dimer. BGP-15, a drug that has been demonstrated to have an anti-arrhythmic effect in mice, stabilized the Kir2.1 current amplitude following VSP-induced PIP₂ depletion in cells expressing WT or mutant dimers. This study underlines the implication of mutations in cytoplasmic regions of Kir2.1. A newly developed calibrated VSP activation protocol enabled a quantitative assessment of changes in PIP₂ regulation caused by the mutations. The results suggest an impaired function and a dominant-negative effect of the Kir2.1 variants that involve an impaired regulation by PIP₂. This study also demonstrates that BGP-15 may be beneficial in restoring impaired Kir2.1 function and possibly in treating ATS symptoms.

Pharmacological Overview of the BGP-15 Chemical Agent as a New Drug Candidate for the Treatment of Symptoms of Metabolic Syndrome

BGP-15 is a new insulin sensitizer drug candidate, which was developed by Hungarian researchers. In recent years, numerous research groups have studied its beneficial effects. It is effective in the treatment of insulin resistance and it has protective effects in Duchenne muscular dystrophy, diastolic dysfunction, tachycardia, heart failure, and atrial fibrillation, and it can alleviate cardiotoxicity. BGP-15 exhibits chemoprotective properties in different cytostatic therapies, and has also proven to be photoprotective. It can additionally have advantageous effects in mitochondrial-stress-related diseases. Although the precise mechanism of the effect is still unknown to us, we know that the molecule is a PARP inhibitor, chaperone co-inducer, reduces ROS production, and is able to remodel the organization of cholesterol-rich membrane domains. In the following review, our aim was to summarize the investigated molecular mechanisms and pharmacological effects of this potential API. The main objective was to present the wide pharmacological potentials of this chemical agent.

The Drug Candidate BGP-15 Delays the Onset of Diastolic Dysfunction in the Goto-Kakizaki Rat Model of Diabetic Cardiomyopathy

Background and Aims: Diabetic cardiomyopathy (DCM) is an emerging problem worldwide due to an increase in the incidence of type 2 diabetes. Animal studies have indicated that metformin and pioglitazone can prevent DCM partly by normalizing insulin resistance, and partly by other, pleiotropic mechanisms. One clinical study has evidenced the insulin-senzitizing effect of the drug candidate BGP-15, along with additional animal studies that have confirmed its beneficial effects in models of diabetes, muscular dystrophy and heart failure, with the drug affecting chaperones, contractile proteins and mitochondria. Our aim was to investigate whether the inzulin-senzitizer BGP-15 exert any additive cardiovascular effects compared to metformin or pioglitazone, using Goto-Kakizaki (GotoK) rats. Methods: Rats were divided into five groups: (I) healthy control (Wistar), (II) diseased (GotoK), and GotoK rats treated with: (III) BGP-15, (IV) metformin, and (V) pioglitazone, respectively, for 12 weeks. Metabolic parameters and insulin levels were determined at the endpoint. Doppler echocardiography was carried out to estimate diabetes-associated cardiac dysfunction. Thoracotomy was performed after the vascular status of rats was evaluated using an isolated aortic ring method. Furthermore, western blot assays were carried out to determine expression or phosphorylation levels of selected proteins that take part in myocyte relaxation. Results: BGP-15 restored diastolic parameters (e′/a′, E/e′, LAP, E and A wave) and improved Tei-index compared to untreated GotoK rats. Vascular status was unaffected by BGP-15. Expression of sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA2a) and phosphodiesterase 9A (PDE9A) were unchanged by the treatments, but the phosphorylation level of vasodilator-stimulated phosphoprotein (VASP) and phospholamban (PLB) increased in BGP-15-treated rats, in comparison to GotoK. Conclusions: Even though the BGP-15-treatment did not interfere significantly with glucose homeostasis and vascular status, it considerably enhanced diastolic function, by affecting the SERCA/phospholamban pathway in GotoK rats. Although it requires further investigation, BGP-15 may offer a new therapeutic approach in DCM.