Increased expression of deltaCaMKII isoforms in skeletal muscle regeneration: Implications in dystrophic muscle disease

A Mango Leaf Extract (Zynamite®) Combined with Quercetin Has Exercise-Mimetic Properties in Human Skeletal Muscle

Zynamite PX^®, a mango leaf extract combined with quercetin, enhances exercise performance by unknown molecular mechanisms. Twenty-five volunteers were assigned to a control (17 males) or supplementation group (8 males, receiving 140 mg of Zynamite^® + 140 mg quercetin/8 h for 2 days). Then, they performed incremental exercise to exhaustion (IE) followed by occlusion of the circulation in one leg for 60 s. Afterwards, the cuff was released, and a 30 s sprint was performed, followed by 90 s circulatory occlusion (same leg). Vastus lateralis muscle biopsies were obtained at baseline, 20 s after IE (occluded leg) and 10 s after Wingate (occluded leg), and bilaterally at 90 s and 30 min post exercise. Compared to the controls, the Zynamite PX^® group showed increased basal protein expression of Thr²⁸⁷-CaMKIIδ_D (2-fold, p = 0.007) and Ser⁹-GSK3β (1.3-fold, p = 0.005) and a non-significant increase of total NRF2 (1.7-fold, p = 0.099) and Ser⁴⁰-NRF2 (1.2-fold, p = 0.061). In the controls, there was upregulation with exercise and recovery of total NRF2, catalase, glutathione reductase, and Thr²⁸⁷-CaMKIIδ_D (1.2-2.9-fold, all p < 0.05), which was not observed in the Zynamite PX^® group. In conclusion, Zynamite PX^® elicits muscle signaling changes in resting skeletal muscle resembling those described for exercise training and partly abrogates the stress kinases responses to exercise as observed in trained muscles.

Neurectomy preserves fast fibers when combined with tenotomy of infraspinatus muscle via upregulation of myogenesis

INTRODUCTION

We evaluated the contribution of denervation-related molecular processes to rotator cuff muscle degeneration after tendon release.

METHODS

We assessed the levels of myogenic (myogenin and myogenic differentiation factor [myoD]) and proadipogenic (peroxisome proliferator-activated receptor γ) transcription factors; the denervation-associated proteins tenascin-C, laminin-2, and calcium/calmodulin-dependent kinase II (CaMKII); and cellular alterations in sheep after infraspinatus tenotomy (TEN), suprascapular neurectomy (NEU), or both (TEN-NEU).

RESULTS

Extracellular ground substance increased at the expense of contractile tissue 16 weeks after surgery, correlating with CaMKII isoform levels. Sheep undergoing NEU and TEN-NEU had exaggerated infraspinatus atrophy and increased fast fibers compared with TEN sheep. The βMCaMKII isoform levels increased with TEN, and myoD levels tripled after denervation and were associated with slow fibers.

DISCUSSION

In sheep, denervation did not affect muscle-to-fat conversion after TEN of the infraspinatus. Furthermore, concurrent NEU mitigated the loss of fast fibers after TEN by inducing a fast-contractile phenotype. Muscle Nerve 59:100-107, 2019.

Muscle Regeneration with Intermuscular Adipose Tissue (IMAT) Accumulation Is Modulated by Mechanical Constraints

Sports trauma are able to induce muscle injury with fibrosis and accumulation of intermuscular adipose tissue (IMAT), which affect muscle function. This study was designed to investigate whether hypoactivity would influence IMAT accumulation in regenerating mouse skeletal muscle using the glycerol model of muscle regeneration. The animals were immediately hindlimb unloaded for 21 days after glycerol injection into the tibialis anterior (TA) muscle. Muscle fiber and adipocyte cross-sectional area (CSA) and IMAT accumulation were determined by histomorphometric analysis. Adipogenesis during regenerative processes was examined using RT-qPCR and Western blot quantification. Twenty-one days of hindlimb unloading resulted in decreases of 38% and 50.6% in the muscle weight/body weight ratio and CSA, respectively, in soleus muscle. Glycerol injection into TA induced IMAT accumulation, reaching 3% of control normal-loading muscle area. This IMAT accumulation was largely inhibited in unloading conditions (0.09%) and concomitant with a marked reduction in perilipin and FABP4 protein content, two key markers of mature adipocytes. Induction of PPARγ and C/EBPα mRNA, two markers of adipogenesis, was also decreased. Furthermore, the protein expression of PDGFRα, a cell surface marker of fibro/adipogenic progenitors, was much lower in regenerating TA from the unloaded group. Exposure of regenerating muscle to hypoactivity severely reduces IMAT development and accumulation. These results provide new insight into the mechanisms regulating IMAT development in skeletal muscle and highlight the importance of taking into account the level of mechanical constraint imposed on skeletal muscle during the regeneration processes.

Brain-Expressed X-linked (BEX) proteins in human cancers

The Brain-Expressed X-linked (BEX) family proteins are comprised of five human proteins including BEX1, BEX2, BEX3, BEX4 and BEX5. BEX family proteins are expressed in a wide range of tissues and are known to play a role in neuronal development. Recent studies suggest a role of BEX family proteins in cancers. BEX1 expression is lost in a subgroup of patients with acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). Expression of BEX1 controls cell surface receptor signaling and restores imatinib response in resistant cells. BEX2 is overexpressed in a group of breast cancer patients and also in gliomas. Increased BEX2 expression led to enhanced NF-κB signaling as well as cell proliferation. Although BEX2 acts as tumor promoter in a subset of breast cancer, BEX3 expression displayed an opposite role. Overexpression of BEX3 resulted in inhibition of tumor formation in breast cancer mouse xenograft models. The role of BEX4 and BEX5 in cancer has not yet been defined. Collectively this suggests that BEX family members have distinct roles in cancers. While BEX1 and BEX3 act as tumor suppressors, BEX2 seems to act as an oncogene.

NRIP is a novel Z-disc protein to activate calmodulin signaling for skeletal muscle contraction and regeneration

Nuclear receptor interaction protein (NRIP, also known as DCAF6 and IQWD1) is a calcium-dependent calmodulin binding protein (Ca2+/CaM). In this study, we found that NRIP is a novel Z-disc protein in skeletal muscle. NRIP knockout mice (NRIP KO) were generated and found to have reduced muscle strength, susceptibility to fatigue and impaired adaptive exercise performance. The mechanisms of NRIP-regulated muscle contraction depend on NRIP being downstream of calcium signaling, where it stimulates phosphorylation of both calcineurin-nuclear factor of activated T-cells, cytoplasmic 1 (CaN-NFATc1) and calmodulin-dependent protein kinase II (CaMKII) through interaction with CaM, resulting in the induction of slow myosin gene expression and mitochondrial activity, and balancing of Ca2+ homeostasis of the internally stored Ca2+ of the sarcoplasmic reticulum. Moreover, NRIP KO mice have delayed regenerative capacity. The amount of NRIP can be enhanced after muscle injury and is responsible for muscle regeneration, coupled with the increased expression of myogenin, desmin and embryonic myosin heavy chain for myogenesis, as well as myotube formation. In conclusion, NRIP is a novel Z-disc protein important for skeletal muscle strength and regenerative capacity.

Differential gene expression in small and large rainbow trout derived from two seasonal spawning groups

Background

Growth in fishes is regulated via many environmental and physiological factors and is shaped by the genetic background of each individual. Previous microarray studies of salmonid growth have examined fish experiencing either muscle wastage or accelerated growth patterns following refeeding, or the influence of growth hormone and transgenesis. This study determines the gene expression profiles of genetically unmanipulated large and small fish from a domesticated salmonid strain reared on a typical feeding regime. Gene expression profiles of white muscle and liver from rainbow trout (Oncorhynchus mykiss) from two seasonal spawning groups (September and December lots) within a single strain were examined when the fish were 15 months of age to assess the influence of season (late fall vs. onset of spring) and body size (large vs. small).

Results

Although IGFBP1 gene expression was up-regulated in the livers of small fish in both seasonal lots, few expression differences were detected in the liver overall. Faster growing Dec. fish showed a greater number of differences in white muscle expression compared to Sept. fish. Significant differences in the GO Generic Level 3 categories ‘response to external stimulus’, ‘establishment of localization’, and ‘response to stress’ were detected in white muscle tissue between large and small fish. Larger fish showed up-regulation of cytoskeletal component genes while many genes related to myofibril components of muscle tissue were up-regulated in small fish. Most of the genes up-regulated in large fish within the ‘response to stress’ category are involved in immunity while in small fish most of these gene functions are related to apoptosis.

Conclusions

A higher proportion of genes in white muscle compared to liver showed similar patterns of up- or down-regulation within the same size class across seasons supporting their utility as biomarkers for growth in rainbow trout. Differences between large and small Sept. fish in the ‘response to stress’ and ‘response to external stimulus’ categories for white muscle tissue, suggests that smaller fish have a greater inability to handle stress compared to the large fish. Sampling season had a significant impact on the expression of genes related to the growth process in rainbow trout.

Role of pericytes in skeletal muscle regeneration and fat accumulation

Stem cells ensure tissue regeneration, while overgrowth of adipogenic cells may compromise organ recovery and impair function. In myopathies and muscle atrophy associated with aging, fat accumulation increases dysfunction, and after chronic injury, the process of fatty degeneration, in which muscle is replaced by white adipocytes, further compromises tissue function and environment. Some studies suggest that pericytes may contribute to muscle regeneration as well as fat formation. This work reports the presence of two pericyte subpopulations in the skeletal muscle and characterizes their specific roles. Skeletal muscle from Nestin-GFP/NG2-DsRed mice show two types of pericytes, Nestin-GFP-/NG2-DsRed+ (type-1) and Nestin-GFP+/NG2-DsRed+ (type-2), in close proximity to endothelial cells. We also found that both Nestin-GFP-/NG2-DsRed+ and Nestin-GFP+/NG2-DsRed+ cells colocalize with staining of two pericyte markers, PDGFRβ and CD146, but only type-1 pericyte express the adipogenic progenitor marker PDGFRα. Type-2 pericytes participate in muscle regeneration, while type-1 contribute to fat accumulation. Transplantation studies indicate that type-1 pericytes do not form muscle in vivo, but contribute to fat deposition in the skeletal muscle, while type-2 pericytes contribute only to the new muscle formation after injury, but not to the fat accumulation. Our results suggest that type-1 and type-2 pericytes contribute to successful muscle regeneration which results from a balance of myogenic and nonmyogenic cells activation.

Deep tissue injury rat model for pressure ulcer research on spinal cord injury

Many rat/mouse pressure ulcer (PU) models have been developed to test different hypotheses to gain deeper understanding of various causative risk factors, the progress of PUs, and assessing effectiveness of potential treatment modalities. The recently emphasized deep tissue injury (DTI) mechanism for PU formation has received increased attention and several studies reported findings on newly developed DTI animal models. However, concerns exist for the clinical relevance and validity of these models, especially when the majority of the reported rat PU/DTI models were not built upon SCI animals and many of the DTI research did not simulate well the clinical observation. In this study, we propose a rat PU and DTI model which is more clinically relevant by including chronic SCI condition into the rat PU model and to simulate the role of bony prominence in DTI formation by using an implant on the bone-tissue interface. Histological data and imaging findings confirmed that the condition of chronic SCI had significant effect on pressure induced tissue injury in a rat PU model and the including a simulated bony prominence in rat DTI model resulted in significantly greater injury in deep muscle tissue. Further integration of the SCI condition and the simulated bony prominence would result a rat PU/DTI model which can simulate even more accurately the clinical phenomenon and yield more clinically relevant findings.

Proteomic analysis of blastema formation in regenerating axolotl limbs

BACKGROUND

Following amputation, urodele salamander limbs reprogram somatic cells to form a blastema that self-organizes into the missing limb parts to restore the structure and function of the limb. To help understand the molecular basis of blastema formation, we used quantitative label-free liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS)-based methods to analyze changes in the proteome that occurred 1, 4 and 7 days post amputation (dpa) through the mid-tibia/fibula of axolotl hind limbs.

RESULTS

We identified 309 unique proteins with significant fold change relative to controls (0 dpa), representing 10 biological process categories: (1) signaling, (2) Ca2+ binding and translocation, (3) transcription, (4) translation, (5) cytoskeleton, (6) extracellular matrix (ECM), (7) metabolism, (8) cell protection, (9) degradation, and (10) cell cycle. In all, 43 proteins exhibited exceptionally high fold changes. Of these, the ecotropic viral integrative factor 5 (EVI5), a cell cycle-related oncoprotein that prevents cells from entering the mitotic phase of the cell cycle prematurely, was of special interest because its fold change was exceptionally high throughout blastema formation.

CONCLUSION

Our data were consistent with previous studies indicating the importance of inositol triphosphate and Ca2+ signaling in initiating the ECM and cytoskeletal remodeling characteristic of histolysis and cell dedifferentiation. In addition, the data suggested that blastema formation requires several mechanisms to avoid apoptosis, including reduced metabolism, differential regulation of proapoptotic and antiapoptotic proteins, and initiation of an unfolded protein response (UPR). Since there is virtually no mitosis during blastema formation, we propose that high levels of EVI5 function to arrest dedifferentiated cells somewhere in the G1/S/G2 phases of the cell cycle until they have accumulated under the wound epidermis and enter mitosis in response to neural and epidermal factors. Our findings indicate the general value of quantitative proteomic analysis in understanding the regeneration of complex structures.

The non-excitable smooth muscle: calcium signaling and phenotypic switching during vascular disease

Calcium (Ca(2+)) is a highly versatile second messenger that controls vascular smooth muscle cell (VSMC) contraction, proliferation, and migration. By means of Ca(2+) permeable channels, Ca(2+) pumps and channels conducting other ions such as potassium and chloride, VSMC keep intracellular Ca(2+) levels under tight control. In healthy quiescent contractile VSMC, two important components of the Ca(2+) signaling pathways that regulate VSMC contraction are the plasma membrane voltage-operated Ca(2+) channel of the high voltage-activated type (L-type) and the sarcoplasmic reticulum Ca(2+) release channel, Ryanodine Receptor (RyR). Injury to the vessel wall is accompanied by VSMC phenotype switch from a contractile quiescent to a proliferative motile phenotype (synthetic phenotype) and by alteration of many components of VSMC Ca(2+) signaling pathways. Specifically, this switch that culminates in a VSMC phenotype reminiscent of a non-excitable cell is characterized by loss of L-type channels expression and increased expression of the low voltage-activated (T-type) Ca(2+) channels and the canonical transient receptor potential (TRPC) channels. The expression levels of intracellular Ca(2+) release channels, pumps and Ca(2+)-activated proteins are also altered: the proliferative VSMC lose the RyR3 and the sarcoplasmic/endoplasmic reticulum Ca(2+) ATPase isoform 2a pump and reciprocally regulate isoforms of the ca(2+)/calmodulin-dependent protein kinase II. This review focuses on the changes in expression of Ca(2+) signaling proteins associated with VSMC proliferation both in vitro and in vivo. The physiological implications of the altered expression of these Ca(2+) signaling molecules, their contribution to VSMC dysfunction during vascular disease and their potential as targets for drug therapy will be discussed.

CaMKII-delta isoform regulation of neointima formation after vascular injury

OBJECTIVE

The purpose of this study was to test the function of the calcium/calmodulin-dependent protein kinase II delta2 isoform (CaMKIIdelta2) in regulating vascular smooth muscle (VSM) cell proliferation and migration in response to vascular injury.

METHODS AND RESULTS

CaMKII isoform content was assessed in rat carotid arteries after balloon angioplasty-induced injury by Western blotting with isoform specific antibodies. Within 3 days after injury, a significant increase in CaMKIIdelta2 and decrease in CaMKIIgamma isoform content was observed in both medial smooth muscle and adventitial fibroblasts. Neointimal VSM cells expressed primarily the delta2 isoform. Incubation of the injured vessel with adenovirus encoding siRNA targeting CaMKIIdelta isoforms prevented upregulation of the delta2 isoform in the media and adventitia; inhibited cell proliferation assessed by PCNA expression in both layers and markedly inhibited neointima formation and adventitial thickening.

CONCLUSIONS

CaMKIIdelta2 is specifically induced in VSM and adventitial fibroblasts during the response of an artery to injury and is a positive regulator of proliferation and migration in the vessel wall contributing to neointima formation and vascular remodeling. This provides a potential mechanism for Ca2+-dependent regulation of VSM and myofibroblast proliferation and migration in response to vascular injury or disease.

Bex1 knock out mice show altered skeletal muscle regeneration

Bex1 and Calmodulin (CaM) are upregulated during skeletal muscle regeneration. We confirm this finding and demonstrate the novel finding that they interact in a calcium-dependent manner. To study the role of Bex1 and its interaction with CaM in skeletal muscle regeneration, we generated Bex1 knock out (Bex1-KO) mice. These mice appeared to develop normally and are fertile, but displayed a functional deficit in exercise performance compared to wild type (WT) mice. After intramuscular injection of cardiotoxin, which causes extensive and reproducible myotrauma followed by recovery, regenerating muscles of Bex1-KO mice exhibited elevated and prolonged cell proliferation, as well as delayed cell differentiation, compared to WT mice. Thus, our results provide the first evidence that Bex1-KO mice show altered muscle regeneration, and allow us to propose that the interaction of Bex1 with Ca(2+)/CaM may be involved in skeletal muscle regeneration.

Effect of endurance exercise training on Ca2+ calmodulin-dependent protein kinase II expression and signalling in skeletal muscle of humans

Here the hypothesis that skeletal muscle Ca(2+)-calmodulin-dependent kinase II (CaMKII) expression and signalling would be modified by endurance training was tested. Eight healthy, young men completed 3 weeks of one-legged endurance exercise training with muscle samples taken from both legs before training and 15 h after the last exercise bout. Along with an approximately 40% increase in mitochondrial F(1)-ATP synthase expression, there was an approximately 1-fold increase in maximal CaMKII activity and CaMKII kinase isoform expression after training in the active leg only. Autonomous CaMKII activity and CaMKII autophosphorylation were increased to a similar extent. However, there was no change in alpha-CaMKII anchoring protein expression with training. Nor was there any change in expression or Thr(17) phosphorylation of the CaMKII substrate phospholamban with training. However, another CaMKII substrate, serum response factor (SRF), had an approximately 60% higher phosphorylation at Ser(103) after training, with no change in SRF expression. There were positive correlations between the increases in CaMKII expression and SRF phosphorylation as well as F(1)ATPase expression with training. After training, there was an increase in cyclic-AMP response element binding protein phosphorylation at Ser(133), but not expression, in muscle of both legs. Taken together, skeletal muscle CaMKII kinase isoform expression and SRF phosphorylation is higher with endurance-type exercise training, adaptations that are restricted to active muscle. This may contribute to greater Ca(2+) mediated regulation during exercise and the altered muscle phenotype with training.