Enhanced survival of skeletal muscle myoblasts in response to overexpression of cold shock protein RBM3

Pre-exercise cryotherapy reduces myoglobin and creatine kinase levels after eccentric muscle stress in young women

Introduction: The aim of this study was to investigate the effect of pre-exercise whole-body cryotherapy (WBC) on muscle damage indicators following eccentric treadmill exercise in young women. Methods: Twenty-seven participants underwent two 1-h downhill treadmill runs, replicating 60% of their maximal oxygen uptake, with a 4-week intermission for recovery and treatment application. In this intermission, one group underwent 20 sessions of WBC, delivered five times a week at -120°C for 3 min each, while the comparison group received no such treatment. Markers of muscle injury-serum myoglobin concentration, creatine kinase and lactate dehydrogenase activity and also uric acid, and cell-free DNA concentration-were measured before and after downhill runs. Results: The study observed a notable reduction in post-exercise myoglobin and CK levels in the WBC group after the second running session. Discussion: The results suggest that WBC can have a protective effects against muscle damage resulting from eccentric exercise.

Identification and validation of a novel Parkinson-Glioma feature gene signature in glioma and Parkinson's disease

Introduction

The prognosis for glioma is generally poor, and the 5-year survival rate for patients with this disease has not shown significant improvement over the past few decades. Parkinson's disease (PD) is a prevalent movement disorder, ranking as the second most common neurodegenerative disease after Alzheimer's disease. Although Parkinson's disease and glioma are distinct diseases, they may share certain underlying biological pathways that contribute to their development.

Objective

This study aims to investigate the involvement of genes associated with Parkinson's disease in the development and prognosis of glioma.

Methods

We obtained datasets from the TCGA, CGGA, and GEO databases, which included RNA sequencing data and clinical information of glioma and Parkinson's patients. Eight machine learning algorithms were used to identify Parkinson-Glioma feature genes (PGFGs). PGFGs associated with glioma prognosis were identified through univariate Cox analysis. A risk signature was constructed based on PGFGs using Cox regression analysis and the Least Absolute Shrinkage and Selection Operator (LASSO) method. We subsequently validated its predictive ability using various methods, including ROC curves, calibration curves, KM survival analysis, C-index, DCA, independent prognostic analysis, and stratified analysis. To validate the reproducibility of the results, similar work was performed on three external test datasets. Additionally, a meta-analysis was employed to observe the heterogeneity and consistency of the signature across different datasets. We also compared the differences in genomic variations, functional enrichment, immune infiltration, and drug sensitivity analysis based on risk scores. This exploration aimed to uncover potential mechanisms of glioma occurrence and prognosis.

Results

We identified 30 PGFGs, of which 25 were found to be significantly associated with glioma survival. The prognostic signature, consisting of 19 genes, demonstrated excellent predictive performance for 1-, 2-, and 3-year overall survival (OS) of glioma. The signature emerged as an independent prognostic factor for glioma overall survival (OS), surpassing the predictive performance of traditional clinical variables. Notably, we observed differences in the tumor microenvironment (TME), levels of immune cell infiltration, immune gene expression, and drug resistance analysis among distinct risk groups. These findings may have significant implications for the clinical treatment of glioma patients.

Conclusion

The expression of genes related to Parkinson's disease is closely associated with the immune status and prognosis of glioma patients, potentially regulating glioma pathogenesis through multiple mechanisms. The interaction between genes associated with Parkinson's disease and the immune system during glioma development provides novel insights into the molecular mechanisms and targeted therapies for glioma.

Cold-shock proteome of myoblasts reveals role of RBM3 in promotion of mitochondrial metabolism and myoblast differentiation

Adaptation to hypothermia is important for skeletal muscle cells under physiological stress and is used for therapeutic hypothermia (mild hypothermia at 32  °C). We show that hypothermic preconditioning at 32  °C for 72 hours improves the differentiation of skeletal muscle myoblasts using both C2C12 and primary myoblasts isolated from 3 month and 18-month-old mice. We analyzed the cold-shock proteome of myoblasts exposed to hypothermia (32  °C for 6 and 48 h) and identified significant changes in pathways related to RNA processing and central carbon, fatty acid, and redox metabolism. The analysis revealed that levels of the cold-shock protein RBM3, an RNA-binding protein, increases with both acute and chronic exposure to hypothermic stress, and is necessary for the enhanced differentiation and maintenance of mitochondrial metabolism. We also show that overexpression of RBM3 at 37  °C is sufficient to promote mitochondrial metabolism, cellular proliferation, and differentiation of C2C12 and primary myoblasts. Proteomic analysis of C2C12 myoblasts overexpressing RBM3 show significant enrichment of pathways involved in fatty acid metabolism, RNA metabolism and the electron transport chain. Overall, we show that the cold-shock protein RBM3 is a critical factor that can be used for controlling the metabolic network of myoblasts.

Extracellular vesicle distribution and localization in skeletal muscle at rest and following disuse atrophy

BACKGROUND

Skeletal muscle (SkM) is a large, secretory organ that produces and releases myokines that can have autocrine, paracrine, and endocrine effects. Whether extracellular vesicles (EVs) also play a role in the SkM adaptive response and ability to communicate with other tissues is not well understood. The purpose of this study was to investigate EV biogenesis factors, marker expression, and localization across cell types in the skeletal muscle. We also aimed to investigate whether EV concentrations are altered by disuse atrophy.

METHODS

To identify the potential markers of SkM-derived EVs, EVs were isolated from rat serum using density gradient ultracentrifugation, followed by fluorescence correlation spectroscopy measurements or qPCR. Single-cell RNA sequencing (scRNA-seq) data from rat SkM were analyzed to assess the EV biogenesis factor expression, and cellular localization of tetraspanins was investigated by immunohistochemistry. Finally, to assess the effects of mechanical unloading on EV expression in vivo, EV concentrations were measured in the serum by nanoparticle tracking analysis in both a rat and human model of disuse.

RESULTS

In this study, we show that the widely used markers of SkM-derived EVs, α-sarcoglycan and miR-1, are undetectable in serum EVs. We also found that EV biogenesis factors, including the tetraspanins CD63, CD9, and CD81, are expressed by a variety of cell types in SkM. SkM sections showed very low detection of CD63, CD9, and CD81 in myofibers and instead accumulation within the interstitial space. Furthermore, although there were no differences in serum EV concentrations following hindlimb suspension in rats, serum EV concentrations were elevated in human subjects after bed rest.

CONCLUSIONS

Our findings provide insight into the distribution and localization of EVs in SkM and demonstrate the importance of methodological guidelines in SkM EV research.

RBM3 is associated with acute lung injury in septic mice and patients via the NF-κB/NLRP3 pathway

Sepsis refers to host response disorders caused by infection, leading to life-threatening organ dysfunction. RNA-binding motif protein 3 (RBM3) is an important cold-shock protein that is upregulated in response to mild hypothermia or hypoxia. In this study, we aimed to investigate whether RBM3 is involved in sepsis-associated acute lung injury (ALI). Intraperitoneal injection of LPS (10 mg/kg) was performed in wild type (WT) and RBM3 knockout (KO, RBM3^-/^-) mice to establish an in vivo sepsis model. An NLRP3 inflammasome inhibitor, MCC950 (50 mg/kg), was injected intraperitoneally 30 min before LPS treatment. Serum, lung tissues, and BALF were collected 24 h later for further analysis. In addition, we also collected serum from sepsis patients and healthy volunteers to detect their RBM3 expression. The results showed that the expression of RBM3 in the lung tissues of LPS-induced sepsis mice and the serum of patients with sepsis was significantly increased and positively correlated with disease severity. In addition, RBM3 knockout (KO) mice had a low survival rate, and RBM3 KO mice had more severe lung damage, inflammation, lung cell apoptosis, and oxidative stress than WT mice. LPS treatment significantly increased the levels of nucleotide binding and oligomerization domain-like receptor family 3 (NLRP3) inflammasomes and mononuclear cell nuclear factor-κB (NF-κB) in the lung tissues of RBM3 KO mice. However, these levels were only slightly elevated in WT mice. Interestingly, MCC950 improved LPS-induced acute lung injury in WT and RBM3 KO mice but inhibited the expression of NLRP3, caspase-1, and IL-1β. In conclusion, RBM3 was overexpressed in sepsis patients and LPS-induced mice. RBM3 gene deficiency aggravated sepsis-associated ALI through the NF-κB/NLRP3 pathway.

The transcript interactome of skeletal muscle RNA binding protein motif 3 (RBM3)

Post-transcriptional regulation of gene expression represents a critical regulatory step in the production of a functional proteome. Elevated expression of post-transcriptional regulator RNA binding motif protein 3 (RBM3), an RNA binding protein in the cold-shock family, is positively correlated with skeletal muscle growth in adult mice. However, mechanisms through which RBM3 exerts its effects are largely unknown. The purpose of this study was to perform RNA immunoprecipitation followed by RNA sequencing (RIP-seq) and apply a network science approach to understand biological processes (BPs) most associated with RBM3-bound mRNAs. In addition, through nucleotide-sequence-scanning of enriched transcripts, we predicted the motif for skeletal muscle RBM3 binding. Gene set enrichment analysis followed by enrichment mapping of RBM3-bound transcripts (fold change >3; p.adj <0.01) revealed significant enrichment of BPs associated with "Contractile apparatus," "Translation initiation," and "Proteosome complex." Clusters were driven largely by enrichment of Myh1 (FC: 4.43), Eif4b (FC: 5.03), and Trim63 (FC: 5.84), respectively. Motif scanning of enriched sequences revealed a discrete 14 nucleotide-wide motif found most prominently at the junction between the protein coding region's termination sequence and the start of the 3' untranslated region (UTR; E-Value: 1.1 e-015 ). Proof of concept investigation of motif location along enriched transcripts Myh1 and Myl4 revealed 3' UTR binding, suggesting RBM3 involvement in transcript half-life regulation. Together, these results demonstrate the potential influence of RBM3 in reshaping the skeletal muscle proteome through post-transcriptional regulation of mRNAs crucial to muscle adaptations.

Delayed denervation-induced muscle atrophy in Opg knockout mice

Recent evidence has shown a crucial role for the osteoprotegerin/receptor activator of nuclear factor κ-B ligand/RANK (OPG/RANKL/RANK) signaling axis not only in bone but also in muscle tissue; however, there is still a lack of understanding of its effects on muscle atrophy. Here, we found that denervated Opg knockout mice displayed better functional recovery and delayed muscle atrophy, especially in a specific type IIB fiber. Moreover, OPG deficiency promoted milder activation of the ubiquitin-proteasome pathway, which further verified the protective role of Opg knockout in denervated muscle damage. Furthermore, transcriptome sequencing indicated that Opg knockout upregulated the expression of Inpp5k, Rbm3, and Tet2 and downregulated that of Deptor in denervated muscle. In vitro experiments revealed that satellite cells derived from Opg knockout mice displayed a better differentiation ability than those acquired from wild-type littermates. Higher expression levels of Tet2 were also observed in satellite cells derived from Opg knockout mice, which provided a possible mechanistic basis for the protective effects of Opg knockout on muscle atrophy. Taken together, our findings uncover the novel role of Opg in muscle atrophy process and extend the current understanding in the OPG/RANKL/RANK signaling axis.

11S Proteasome Activator REGγ Promotes Aortic Dissection by Inhibiting RBM3 (RNA Binding Motif Protein 3) Pathway

BACKGROUND

Aortic dissection (AD) is a life-threatening cardiovascular disorder with high mortality and lacking underlying mechanisms or effective treatments. REGγ, the 11S proteasome activator known to promote the degradation of cellular proteins in a ubiquitin- and ATP-independent manner, emerges as a new regulator in the cardiovascular system.

METHODS

Using β-aminopropionitrile (BAPN)-subjected REGγ knockout AD mice and Ang II (angiotensin II)-treated REGγ deficiency vascular smooth muscle cells (VSMCs) to explore the effect of REGγ in AD progression.

RESULTS

REGγ was upregulated in mouse aorta of β-aminopropionitrile-induced AD model in vivo and Ang II-treated VSMCs in vitro. REGγ deficiency ameliorated AD progression in β-aminopropionitrile-induced mice by protecting against the switch in VSMCs from contractile to synthetic phenotype through suppressing RBM3 (RNA-binding motif protein 3) decay. Mechanically, REGγ interacted with and degraded the RNA-binding protein RBM3 directly, leading to decreased mRNA stability, lowered expression and transcriptional activity of transcription factor SRF (serum response factor), subsequently reduced transcription of VSMCs-specific contractile genes, α-SMA (alpha-smooth muscle actin) and SM22α (smooth muscle 22 alpha), caused the switch in VSMCs from contractile to synthetic phenotype and associated AD progression. Ablation of endogenous SRF or RBM3, or overexpressing exogenous RBM3 in VSMCs significantly blocked or reestablished the REGγ-dependent action on VSMCs phenotypic switch of Ang II stimulation in vitro. Furthermore, exogenously introducing RBM3 improved the switch in VSMCs from contractile to synthetic phenotype and associated AD features caused by REGγ in vivo.

CONCLUSIONS

Our results demonstrated that REGγ promoted the switch in VSMCs from contractile to synthetic phenotype and AD progression by inhibiting RBM3-SRF pathway, indicated that modulating REGγ-proteasome activity may be a potential therapeutic approach for AD-associated cardiovascular dysfunction.

RNA binding motif protein 3 (RBM3) promotes protein kinase B (AKT) activation to enhance glucose metabolism and reduce apoptosis in skeletal muscle of mice under acute cold exposure

The main danger of cold stress to animals in cold regions is systemic metabolic changes and protein synthesis inhibition. RBM3, an exceptional cold shock protein, is rapidly upregulated in response to hypothermia to resist the adverse effects of cold stress. However, the mechanism of the protective effect and the rapid upregulation of RBM3 remains unclear. O-GlcNAcylation, an atypical O-glycosylation, is precisely regulated only by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) and participates in the signal transduction of multiple cellular stress responses as a "stress and nutrition receptor." Therefore, our study aimed to explore the mechanism of RBM3 regulating glucose metabolism and promoting survival in skeletal muscle under acute cold exposure. Meanwhile, our study verifies whether O-GlcNAcylation mediated by OGT rapidly upregulates RBM3. The blood and skeletal muscle of mice were collected at the end of cold exposure treatment for 0, 2, and 4 h. Changes in levels of RBM3, AKT, glycolysis apoptosis, and OGT were measured. The results show that acute cold exposure upregulated RBM3, OGT, and AKT phosphorylation and increased energy consumption, which enhanced glycolysis and prevent apoptosis. In the 32 °C mild hypothermia model in vitro, overexpression of RBM3 enhanced AKT phosphorylation. Meanwhile, inactivation of AKT by wortmannin resulted in increased apoptosis and decreased glucose metabolism in skeletal muscle under acute cold exposure. In addition, OGT-mediated O-GlcNAcylation of p65 was confirmed in mouse myoblast cell line (C2C12) cells at mild hypothermia. O-GlcNAcylation level affected p65 activity and nuclear translocation. Compared with wild type (WT) mice, RBM3 and p65 phosphorylation were decreased in specific skeletal muscle Ogt (KO) mice, whereas AKT phosphorylation, glycolysis, and apoptosis were increased. Taken together, O-GlcNAcylation of p65 upregulates RBM3 to promote AKT phosphorylation, enhance glucose metabolism, and reduce apoptosis in skeletal muscle of mice under acute cold exposure.

Angiostatic freeze or angiogenic move? Acute cold stress prevents angiokine secretion from murine myotubes but primes primary endothelial cells for greater migratory capacity

The skeletal muscle tissue can adapt to exercise and environmental stressors with a remarkable plasticity. Prolonged cold stress exposure has been associated to increased skeletal muscle capillarization. Angioadaptation refers to the coordinated molecular and cellular processes that influence the remodeling of skeletal muscle microvasculature. Two cell types are central to angioadaptation: the myocytes, representing an important source of angiokines; and the skeletal muscle endothelial cell (SMECs), targets of these angiokines and main constituents of muscle capillaries. The influence of cold stress on skeletal muscle angioadaptation remains largely unknown, particularly with respect to myocyte-specific angiokines secretion or endothelial cell angioadaptive responses. Here, we use an in vitro model to investigate the impact of cold stress (28°C versus 37°C) on C2C12 myotubes and SMECs. Our main objectives were to evaluate: 1) the direct impact of cold stress on C2C12 cellular expression of angiokines and their release in the extracellular environment; 2) the indirect impact of cold stress on SMECs migration via these C2C12-derived angiokines; and 3) the direct effect of cold stress on SMECs angioadaptive responses, including migration, proliferation, and the activation of the vascular endothelial growth factor receptor-2 (VEGFR2). Cold stress reduced the secretion of angiokines in C2C12 myotubes culture media irrespective their pro-angiogenic or angiostatic nature. In SMECs, cold stress abrogated cell proliferation and reduced the activation of VEGFR2 despite a greater expression of this receptor. Finally, SMECs pre-conditioned to cold stress displayed an enhanced migratory response when migration was stimulated in rewarming conditions. Altogether our results suggest that cold stress may be overall angiostatic. However, cold stress accompanied by rewarming may be seen as a pro-angiogenic stressor for SMECs. This observation questions the potential for using pre-cooling in sport-performance or therapeutic exercise prescription to enhance skeletal muscle angioadaptive responses to exercise.

The effects of temperature and donor piglet age on the transcriptomic profile and energy metabolism of myoblasts

Rapid climate change is associated with frequent extreme heat events and the resulting thermal stress has consequences for the health, welfare, and growth of farm animals. The aim of this study was to characterize the transcriptional changes and the effects on energy metabolism in proliferating porcine myoblasts derived from piglets of different ages, representing differences in thermoregulatory abilities, and cultivated below (35°C) and above (39°C, 41°C) the standard cultivation temperature (37°C). Satellite cells originating from Musculus rhomboideus of piglets isolated on days 5 (P5, thermolabile) and 20 (P20, thermostable) of age were used. Our expression analyses highlighted differentially expressed genes in porcine myoblasts cultures under heat or cold induced stress. These gene sets showed enrichment for biological processes and pathways related to organelle fission, cell cycle, chromosome organization, and DNA replication. Culture at 35°C resulted in increased metabolic flux as well as a greater abundance of transcripts of the cold shock protein-encoding gene RBM3 and those of genes related to biological processes and signaling pathways, especially those involving the immune system (cytokine–cytokine receptor interaction, TNF and IL-17 signaling pathways). For cultivation at 39°C, differences in the expression of genes related to DNA replication and cell growth were identified. The highest glutathione index ratio was also found under 39°C. Meanwhile, cultivation at 41°C induced a heat stress response, including the upregulation of HSP70 expression and the downregulation of many biological processes and signaling pathways related to proliferative ability. Our analysis also identified differentially expressed genes between cells of donors with a not yet (P5) and already fully developed (P20) capacity for thermoregulation at different cultivation temperatures. When comparing P5 and P20, most of the changes in gene expression were detected at 37°C. At this optimal temperature, muscle cells can develop to their full capacity. Therefore, the most diverse molecular signaling pathways, including PI3K-Akt signaling, Wnt signaling, and EGFR tyrosine kinase inhibitor, were found and are more pronounced in muscle cells from 20-day-old piglets. These results contribute to a better understanding of the mechanisms underlying the adaptation of skeletal muscle cells to temperature stress in terms of their thermoregulatory ability.

RBM3 is an outstanding cold shock protein with multiple physiological functions beyond hypothermia

RNA-binding motif protein 3 (RBM3), an outstanding cold shock protein, is rapidly upregulated to ensure homeostasis and survival in a cold environment, which is an important physiological mechanism in response to cold stress. Meanwhile, RBM3 has multiple physiological functions and participates in the regulation of various cellular physiological processes, such as antiapoptosis, circadian rhythm, cell cycle, reproduction, and tumogenesis. The structure, conservation, and tissue distribution of RBM3 in human are demonstrated in this review. Herein, the multiple physiological functions of RBM3 were summarized based on recent research advances. Meanwhile, the cytoprotective mechanism of RBM3 during stress under various adverse conditions and its regulation of transcription were discussed. In addition, the neuroprotection of RBM3 and its oncogenic role and controversy in various cancers were investigated in our review.

Time-resolved proteome and transcriptome of paraquat-induced pulmonary fibrosis

BACKGROUNDS

Pulmonary fibrosis (PF) is a pathological state presenting at the progressive stage of heterogeneous interstitial lung disease (ILD). The current understanding of the molecular mechanisms involved is incomplete. This clinical toxicology study focused on the pulmonary fibrosis induced by paraquat (PQ), a widely-used herbicide. Using proteo-transcriptome analysis, we identified differentially expressed proteins (DEPs) derived from the initial development of fibrosis to the dissolved stage and provided further functional analysis.

METHODS

We established a mouse model of progressive lung fibrosis via intratracheal instillation of paraquat. To acquire a comprehensive and unbiased understanding of the onset of pulmonary fibrosis, we performed time-series proteomics profiling (iTRAQ) and RNA sequencing (RNA-Seq) on lung samples from paraquat-treated mice and saline control. The biological functions and pathways involved were evaluated through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway analysis. Correlation tests were conducted on comparable groups 7 days and 28 days post-exposure. Differentially expressed proteins and genes following the same trend on the protein and mRNA levels were selected for validation. The functions of the selected molecules were identified in vitro. The protein level was overexpressed by transfecting gene-containing plasmid or suppressed by transfecting specific siRNA in A549 cells. The levels of endothlial-mesenchymal transition (EMT) markers, including E-cadherin, vimentin, FN1, and α-SMA, were determined via western blot to evaluate the fibrotic process.

RESULTS

We quantified 1358 DEPs on day 7 and 426 DEPs on day 28 post exposure (Fold change >1.2; Q value < 0.05). The top 5 pathways - drug metabolism-cytochrome P450, metabolism of xenobiotics by cytochrome P450, complement and coagulation cascades, chemical carcinogenesis, protein digestion and absorption - were involved on both day 7 and day 28. Several pathways, including tight junction, focal adhesion, platelet activation, and ECM-receptor interaction, were more enriched on day 28 than on day 7. Integrative analysis of the proteome and transcriptome revealed a moderate correlation of quantitative protein abundance ratios with RNA abundance ratios (Spearman R = 0.3950 and 0.2477 on days 7 and 28, respectively), indicating that post-transcriptional regulation plays an important role in lung injury and repair. Western blot identified that the protein expressions of FN1, S100A4, and RBM3 were significantly upregulated while that of CYP1A1, FMO3, and PGDH were significantly downregulated on day 7. All proteins generally recovered to baseline on day 28. qPCR showed the mRNA levels of Fn1, S100a4, Rbm3, Cyp1a1, Fmo3, and Hpgd changed following the same trend as the levels of their respective proteins. Further, in vitro experiments showed that RBM3 was upregulated while PGDH was downregulated in an EMT model established in human lung epithelial A549 cells. RBM3 overexpression and PGDH knockout could both induce EMT in A549 cells. RBM3 knockout or PGDH overexpression had no reverse effect on EMT in A549 cells.

CONCLUSIONS

Our proteo-transcriptomic study determined the proteins responsible for fibrogenesis and uncovers their dynamic regulation from lung injury to repair, providing new insights for the development of biomarkers for diagnosis and treatment of fibrotic diseases.

RNA-Binding Proteins in the Post-transcriptional Control of Skeletal Muscle Development, Regeneration and Disease

Embryonic myogenesis is a temporally and spatially regulated process that generates skeletal muscle of the trunk and limbs. During this process, mononucleated myoblasts derived from myogenic progenitor cells within the somites undergo proliferation, migration and differentiation to elongate and fuse into multinucleated functional myofibers. Skeletal muscle is the most abundant tissue of the body and has the remarkable ability to self-repair by re-activating the myogenic program in muscle stem cells, known as satellite cells. Post-transcriptional regulation of gene expression mediated by RNA-binding proteins is critically required for muscle development during embryogenesis and for muscle homeostasis in the adult. Differential subcellular localization and activity of RNA-binding proteins orchestrates target gene expression at multiple levels to regulate different steps of myogenesis. Dysfunctions of these post-transcriptional regulators impair muscle development and homeostasis, but also cause defects in motor neurons or the neuromuscular junction, resulting in muscle degeneration and neuromuscular disease. Many RNA-binding proteins, such as members of the muscle blind-like (MBNL) and CUG-BP and ETR-3-like factors (CELF) families, display both overlapping and distinct targets in muscle cells. Thus they function either cooperatively or antagonistically to coordinate myoblast proliferation and differentiation. Evidence is accumulating that the dynamic interplay of their regulatory activity may control the progression of myogenic program as well as stem cell quiescence and activation. Moreover, the role of RNA-binding proteins that regulate post-transcriptional modification in the myogenic program is far less understood as compared with transcription factors involved in myogenic specification and differentiation. Here we review past achievements and recent advances in understanding the functions of RNA-binding proteins during skeletal muscle development, regeneration and disease, with the aim to identify the fundamental questions that are still open for further investigations.

Exosomal miR-335 derived from mature dendritic cells enhanced mesenchymal stem cell-mediated bone regeneration of bone defects in athymic rats

BACKGROUND

Transplantation of bone marrow-derived mesenchymal stem cells (BM-MSCs) embedded in a bio-compatible matrix has been demonstrated as a promising strategy for the treatment of bone defects. This study was designed to explore the effect and mechanism of exosomes derived from mature dendritic cells (mDC-Exo) on the BM-MSCs-mediated bone regeneration using the matrix support in an athymic rat model of femoral bone defect.

METHODS

The BM-MSCs were isolated from rats and incubated with osteoblast induction medium, exosomes derived from immature DCs (imDC-Exo), mDC-Exo, and miR-335-deficient mDC-Exo. BM-MSCs treated without or with mDC-Exo were embedded in a bio-compatible matrix (Orthoss®) and then implanted into the femoral bone defect of athymic rats.

RESULTS

mDC-Exo promoted the proliferation and osteogenic differentiation of BM-MSCs by transferring miR-335. Mechanistically, exosomal miR-335 inhibited Hippo signaling by targeting large tongue suppressor kinase 1 (LATS1) and thus promoted the proliferation and osteogenic differentiation of BM-MSCs. Animal experiments showed that mDC-Exo enhanced BM-MSCs-mediated bone regeneration after bone defect, and this effect was abrogated when miR-335 expression was inhibited in mDC-Exo.

CONCLUSION

mDC-Exo promoted osteogenic differentiation of BM-MSCs and enhanced BM-MSCs-mediated bone regeneration after femoral bone defect in athymic rats by transferring miR-335.

Age-related responses to a bout of mechanotherapy in skeletal muscle of rats

Cyclic compressive loading (CCL) is a massage mimetic that improves muscle regrowth from atrophy in adult rats. Therefore, we tested if a single bout of CCL increases anabolic signaling and protein synthesis in muscle during normal, weight-bearing conditions in gastrocnemius muscle from adult and aged rats. Male Brown Norway/F344 rats at 10 (adult) and 30 (aged) months of age were assigned control or CCL (receiving a single bout of CCL). Twenty-four hours following a single bout of CCL there was no change in protein synthesis, Akt, or GSK3β signaling at either age, despite adult rats having higher abundance and activation of mechanosensitive pathways (integrins and integrin-linked kinase). Murf1 was elevated in response to CCL in both age groups, potentially indicating muscle remodeling. Muscle from aged rats exhibited an increase in heat shock protein (HSP) 25 and HSP70 and in the cold shock protein RNA-binding motif 3 (RBM3), demonstrating a unique stress response to CCL in aged muscle only. Finally, muscle from aged rats exhibited higher basal protein synthesis that was corroborated by elevated eIF2Bε and rpS6 signaling, without an additional effect of CCL. In summary, a single bout of CCL does not have anabolic effects on skeletal muscle during normal, weight-bearing conditions, even though it has previously been shown to improve regrowth from atrophy. These data demonstrate that interventions that may help recover from atrophy do not necessarily induce muscle hypertrophy in unperturbed conditions.NEW & NOTEWORTHY Massage has been demonstrated to be an effective mechanotherapy to improve recovery from atrophy in adult skeletal muscle; however, this study shows that a single bout of massage fails to increase protein synthesis or anabolic signaling in adult or aged skeletal muscle during normal, weight-bearing conditions. Altogether, our data suggest massage is a useful mechanotherapy for preserving skeletal muscle when combined with other interventions but is not an anabolic stimulus on its own.

Post-TTM Rebound Pyrexia after Ischemia-Reperfusion Injury Results in Sterile Inflammation and Apoptosis in Cardiomyocytes

Introduction

Fever is frequently observed after acute ischemic events and is associated with poor outcome and higher mortality. Targeted temperature management (TTM) is recommended for neuroprotection in comatose cardiac arrest survivors, but pyrexia after rewarming is proven to be detrimental in clinical trials. However, the cellular mechanisms and kinetics of post-TTM rebound pyrexia remain to be elucidated. Therefore, we investigated the effects of cooling and post-TTM pyrexia on the inflammatory response and apoptosis in a cardiomyocyte ischemia-reperfusion (IR) injury model.

Methods

HL-1 cardiomyocytes were divided into the following groups to investigate the effect of oxygen-glucose deprivation/reperfusion (OGD/R), hypothermia (33.5°C), and pyrexia (40°C): normoxia controls maintained at 37°C and warmed to 40°C, OGD/R groups maintained at 37°C and cooled to 33.5°C for 24 h with rewarming to 37°C, and OGD/R pyrexia groups further warmed from 37 to 40°C. Caspase-3 and RBM3 were assessed by Western blot and TNF-α, IL-6, IL-1β, SOCS3, iNOS, and RBM3 transcriptions by RT-qPCR.

Results

OGD-induced oxidative stress (iNOS) in cardiomyocytes was attenuated post-TTM by cooling. Cytokine transcriptions were suppressed by OGD, while reperfusion induced significant TNF-α transcription that was exacerbated by cooling. Significant inductions of TNF-α, IL-6, IL-1β, and SOCS3 were observed in noncooled, but not in cooled and rewarmed, OGD/R-injured cardiomyocytes. Further warming to pyrexia induced a sterile inflammatory response in OGD/R-injured groups that was attenuated by previous cooling, but no inflammation was observed in pyrexic normoxia groups. Moreover, cytoprotective RBM3 expression was induced by cooling but suppressed by pyrexia, correlating with apoptotic caspase-3 activation.

Conclusion

Our findings show that maintaining a period of post-TTM “therapeutic normothermia” is effective in preventing secondary apoptosis-driven myocardial cell death, thus minimizing the infarct area and further release of mediators of the innate sterile inflammatory response after acute IR injury.

Cold-inducible protein RBM3 mediates hypothermic neuroprotection against neurotoxin rotenone via inhibition on MAPK signalling

Mild hypothermia and its key product, cold-inducible protein RBM3, possess robust neuroprotective effects against various neurotoxins. However, we previously showed that mild hypothermia fails to attenuate the neurotoxicity from MPP+ , one of typical neurotoxins related to the increasing risk of Parkinson disease (PD). To better understand the role of mild hypothermia and RBM3 in PD progression, another known PD-related neurotoxin, rotenone (ROT) was utilized in this study. Using immunoblotting, cell viability assays and TUNEL staining, we revealed that mild hypothermia (32°C) significantly reduced the apoptosis induced by ROT in human neuroblastoma SH-SY5Y cells, when compared to normothermia (37°C). Meanwhile, the overexpression of RBM3 in SH-SY5Y cells mimicked the neuroprotective effects of mild hypothermia on ROT-induced cytotoxicity. Upon ROT stimulation, MAPK signalling like p38, JNK and ERK, and AMPK and GSK-3β signalling were activated. When RBM3 was overexpressed, only the activation of p38, JNK and ERK signalling was inhibited, leaving AMPK and GSK-3β signalling unaffected. Similarly, mild hypothermia also inhibited the activation of MAPKs induced by ROT. Lastly, it was demonstrated that the MAPK (especially p38 and ERK) inhibition by their individual inhibitors significantly decreased the neurotoxicity of ROT in SH-SY5Y cells. In conclusion, these data demonstrate that RBM3 mediates mild hypothermia-related neuroprotection against ROT by inhibiting the MAPK signalling of p38, JNK and ERK.

Limited Oxidative Stress Favors Resistance to Skeletal Muscle Atrophy in Hibernating Brown Bears (Ursus Arctos)

Oxidative stress, which is believed to promote muscle atrophy, has been reported to occur in a few hibernators. However, hibernating bears exhibit efficient energy savings and muscle protein sparing, despite long-term physical inactivity and fasting. We hypothesized that the regulation of the oxidant/antioxidant balance and oxidative stress could favor skeletal muscle maintenance in hibernating brown bears. We showed that increased expressions of cold-inducible proteins CIRBP and RBM3 could favor muscle mass maintenance and alleviate oxidative stress during hibernation. Downregulation of the subunits of the mitochondrial electron transfer chain complexes I, II, and III, and antioxidant enzymes, possibly due to the reduced mitochondrial content, indicated a possible reduction of the production of reactive oxygen species in the hibernating muscle. Concomitantly, the upregulation of cytosolic antioxidant systems, under the control of the transcription factor NRF2, and the maintenance of the GSH/GSSG ratio suggested that bear skeletal muscle is not under a significant oxidative insult during hibernation. Accordingly, lower levels of oxidative damage were recorded in hibernating bear skeletal muscles. These results identify mechanisms by which limited oxidative stress may underlie the resistance to skeletal muscle atrophy in hibernating brown bears. They may constitute therapeutic targets for the treatment of human muscle atrophy.

Neuroprotection by Therapeutic Hypothermia

Hypothermia therapy is an old and important method of neuroprotection. Until now, many neurological diseases such as stroke, traumatic brain injury, intracranial pressure elevation, subarachnoid hemorrhage, spinal cord injury, hepatic encephalopathy, and neonatal peripartum encephalopathy have proven to be suppressed by therapeutic hypothermia. Beneficial effects of therapeutic hypothermia have also been discovered, and progress has been made toward improving the benefits of therapeutic hypothermia further through combination with other neuroprotective treatments and by probing the mechanism of hypothermia neuroprotection. In this review, we compare different hypothermia induction methods and provide a summarized account of the synergistic effect of hypothermia therapy with other neuroprotective treatments, along with an overview of hypothermia neuroprotection mechanisms and cold/hypothermia-induced proteins.

RNA-binding proteins: The next step in translating skeletal muscle adaptations?

The decline of skeletal muscle mass during illness, injury, disuse, and aging is associated with poor health outcomes. Therefore, it is important to pursue a greater understanding of the mechanisms that dictate skeletal muscle adaptation. In this review, we propose that RNA-binding proteins (RBPs) comprise a critical regulatory node in the orchestration of adaptive responses in skeletal muscle. While RBPs have broadly pleiotropic molecular functions, our discussion is constrained at the outset by observations from hibernating animals, which suggest that RBP regulation of RNA stability and its impact on translational reprogramming is a key component of skeletal muscle response to anabolic and catabolic stimuli. We discuss the limited data available on the expression and functions of RBPs in adult skeletal muscle in response to disuse, aging, and exercise. A model is proposed in which dynamic changes in RBPs play a central role in muscle adaptive processes through their differential effects on mRNA stability. While limited, the currently available data suggest that understanding how adaptive (and maladaptive) changes in the expression of RBPs regulate mRNA stability in skeletal muscle could be an informative and productive research area for finding new strategies to limit atrophy and promote hypertrophy.

Regulating glycolysis, the TLR4 signal pathway and expression of RBM3 in mouse liver in response to acute cold exposure

At low temperatures, the liver increases glucose utilization and expresses RNA-binding motif 3 (RBM3) to cope with cold exposure. In this study, the expression of heat shock protein 70 (HSP70), Toll-like receptor 4 (TLR4), bone marrow differentiation factor 88 (MYD88), and phosphorylated nuclear factor-κB (NF-κB) was consistent with fluctuations in insulin in fasted cold-exposed mice. We also found up-regulation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) in acute cold exposure with a decrease in core body temperature. RBM3 transcription and translation were activated 2 h after cold exposure. The anti-apoptotic factor Bcl-2/Bax ratio also increased, while expression of apoptosis factors: cleaved caspase-3, cleaved poly(ADP-ribose)polymerase 1 (PARP-1) and cytochrome-c (Cyt-c) was unchanged. Liver glycogen was depleted after 2 h of cold exposure, and blood glucose decreased after 4 h. Glycogen synthase kinase 3β (GSK3β) phosphorylation continued to increase to promote hepatic glycogen synthesis. We found a high level of protein kinase B (AKT) phosphorylation after 6 h of cold exposure. In addition, we demonstrated that after cold exposure for 2 h, in the liver, continued phosphorylation of fructose-2,6-diphosphate (PFKFB2) and decreased accumulation of glycogen intermediates fructose-1,6-diphosphate (FDP) and pyruvic acid (PA). In summary, the liver responds to cold exposure through a number of different pathways, including activation of HSP70/TLR4 signaling pathways, up-regulation of RBM3 expression, and increased glycolysis and glycogen synthesis. We propose a possible signaling pathway in which regulation of RBM3 expression by the liver affects the AKT metabolic signaling pathway. Lay summary In response to changes in ambient temperature, mice regulate global metabolism and gene expression through hormones. This study focused on the effects of environmental hypothermia on molecular pathways of glucose metabolism in the liver, which is the important metabolic organ in mice. This provides a basis for further study of mice against cold exposure damage.

Skeletal muscle cold shock and heat shock protein mRNA response to aerobic exercise in different environmental temperatures

The response of cold shock proteins to exercise and environmental temperature in human skeletal muscle is not known. The purpose of this study was to determine the early mRNA response of human stress proteins to endurance exercise and environmental temperatures. Seven recreationally trained males cycled for 1 hour at 60% VO_2peak in 7°C, 20°C, and 33°C with biopsies taken pre- and 3 hours post-exercise. Gene expression for heat shock and cold shock proteins were analyzed using qRT-PCR on muscle biopsy samples from the vastus lateralis. RBM3 mRNA was reduced 1.43 ± 0.10 fold (p = 0.006) while there was a trend for CIRP to decrease1.27 ± 0.14 fold (p = 0.059) from pre- to 3 h post-exercise. CIRP and RBM3 mRNA were not different between temperatures (p = 0.273 and p = 0.686, respectively). HSP70 mRNA was 2.27 ± 0.23 fold higher 3 h post-exercise when compared to pre-exercise (p = 0.002) but was not significantly different between temperatures (p = 0.103). HSP27, HSP90, and HSF1 mRNA did not change from pre- to post-exercise (p = 0.052, p = 0.324, p = 0.795) and were not different between temperatures (p = 0.247, p = 0.134, p = 0.808). These data indicate that exposure to mild heat and cold during aerobic exercise have limited effect on the skeletal muscle mRNA expression of heat shock and cold shock proteins. However, skeletal muscle mRNA of cold shock proteins decrease, while HSP70 mRNA increases in response to a low to moderate intensity aerobic exercise bout.

A New Vision for Therapeutic Hypothermia in the Era of Targeted Temperature Management: A Speculative Synthesis

Three decades of animal studies have reproducibly shown that hypothermia is profoundly cerebroprotective during or after a central nervous system (CNS) insult. The success of hypothermia in preclinical acute brain injury has not only fostered continued interest in research on the classic secondary injury mechanisms that are prevented or blunted by hypothermia but has also sparked a surge of new interest in elucidating beneficial signaling molecules that are increased by cooling. Ironically, while research into cold-induced neuroprotection is enjoying newfound interest in chronic neurodegenerative disease, conversely, the scope of the utility of therapeutic hypothermia (TH) across the field of acute brain injury is somewhat controversial and remains to be fully defined. This has led to the era of Targeted Temperature Management, which emphasizes a wider range of temperatures (33–36°C) showing benefit in acute brain injury. In this comprehensive review, we focus on our current understandings of the novel neuroprotective mechanisms activated by TH, and discuss the critical importance of developmental age germane to its clinical efficacy. We review emerging data on four cold stress hormones and three cold shock proteins that have generated new interest in hypothermia in the field of CNS injury, to create a framework for new frontiers in TH research. We make the case that further elucidation of novel cold responsive pathways might lead to major breakthroughs in the treatment of acute brain injury, chronic neurological diseases, and have broad potential implications for medicines of the distant future, including scenarios such as the prevention of adverse effects of long-duration spaceflight, among others. Finally, we introduce several new phrases that readily summarize the essence of the major concepts outlined by this review—namely, Ultramild Hypothermia, the “Responsivity of Cold Stress Pathways,” and “Hypothermia in a Syringe.”

The Influence of Post-Exercise Cold-Water Immersion on Adaptive Responses to Exercise: A Review of the Literature

Post-exercise cold-water immersion (CWI) is used extensively in exercise training as a means to minimise fatigue and expedite recovery between sessions. However, debate exists around its merit in long-term training regimens. While an improvement in recovery following a single session of exercise may improve subsequent training quality and stimulus, reports have emerged suggesting CWI may attenuate long-term adaptations to exercise training. Recent developments in the understanding of the molecular mechanisms governing the adaptive response to exercise in human skeletal muscle have provided potential mechanistic insight into the effects of CWI on training adaptations. Preliminary evidence suggests that CWI may blunt resistance signalling pathways following a single exercise session, as well as attenuate key long-term resistance training adaptations such as strength and muscle mass. Conversely, CWI may augment endurance signalling pathways and the expression of genes key to mitochondrial biogenesis following a single endurance exercise session, but have little to no effect on the content of proteins key to mitochondrial biogenesis following long-term endurance training. This review explores current evidence regarding the underlying molecular mechanisms by which CWI may alter cellular signalling and the long-term adaptive response to exercise in human skeletal muscle.

Cold shock protein RBM3 attenuates atrophy and induces hypertrophy in skeletal muscle

RNA-binding motif protein 3 (RBM3), a stress-inducible RNA-binding protein that increases protein synthesis and confers cell protection in multiple cell types, has been identified as a possible regulator of skeletal muscle mass. Therefore, the primary aim of this study was to examine the impact of elevated RBM3 on skeletal muscle hypertrophy and resistance to atrophy. Plasmid-mediated overexpression of RBM3 in vitro and in vivo was used to assess the role of RBM3 in muscle. C₂C₁₂ myotubes overexpressing RBM3 were approximately 1.6 times larger than non-transfected myotubes, suggesting a role for RBM3 in hypertrophy. In addition, elevated RBM3 attenuated atrophy in myotubes exposed to dexamethasone. In agreement with in vitro results, overexpression of RBM3 in soleus muscle of F344/BN rats using electroporation techniques increased the cross sectional area of muscle fibers. Overexpression of RBM3 also attenuated muscle atrophy in rat soleus muscle undergoing disuse atrophy. These findings provide direct evidence for a novel role of RBM3 in inducing hypertrophy as well as attenuating atrophy.

Morphoregulatory functions of the RNA-binding motif protein 3 in cell spreading, polarity and migration

RNA-binding proteins are emerging as key regulators of transitions in cell morphology. The RNA-binding motif protein 3 (RBM3) is a cold-inducible RNA-binding protein with broadly relevant roles in cellular protection, and putative functions in cancer and development. Several findings suggest that RBM3 has morphoregulatory functions germane to its roles in these contexts. For example, RBM3 helps maintain the morphological integrity of cell protrusions during cell stress and disease. Moreover, it is highly expressed in migrating neurons of the developing brain and in cancer invadopodia, suggesting roles in migration. We here show that RBM3 regulates cell polarity, spreading and migration. RBM3 was present in spreading initiation centers, filopodia and blebs that formed during cell spreading in cell lines and primary myoblasts. Reducing RBM3 triggered exaggerated spreading, increased RhoA expression, and a loss of polarity that was rescued by Rho kinase inhibition and overexpression of CRMP2. High RBM3 expression enhanced the motility of cells migrating by a mesenchymal mode involving extension of long protrusions, whereas RBM3 knockdown slowed migration, greatly reducing the ability of cells to extend protrusions and impairing multiple processes that require directional migration. These data establish novel functions of RBM3 of potential significance to tissue repair, metastasis and development.

Cold Shock Induced Protein RBM3 but Not Mild Hypothermia Protects Human SH-SY5Y Neuroblastoma Cells From MPP+-Induced Neurotoxicity

The cold shock protein RBM3 can mediate mild hypothermia-related protection in neurodegeneration such as Alzheimer's disease. However, it remains unclear whether RBM3 and mild hypothermia provide same protection in model of Parkinson's disease (PD), the second most common neurodegenerative disorder. In this study, human SH-SY5Y neuroblastoma cells subjected to insult by 1-methyl-4-phenylpyridinium (MPP+) served as an in-vitro model of PD. Mild hypothermia (32°C) aggravated MPP+-induced apoptosis, which was boosted when RBM3 was silenced by siRNA. In contrast, overexpression of RBM3 significantly reduced this apoptosis. MPP+ treatment downregulated the expression of RBM3 both endogenously and exogenously and suppressed its induction by mild hypothermia (32°C). In conclusion, our data suggest that cold shock protein RBM3 provides neuroprotection in a cell model of PD, suggesting that RBM3 induction may be a suitable strategy for PD therapy. However, mild hypothermia exacerbates MPP+-induced apoptosis even that RBM3 could be synthesized during mild hypothermia.

Local cryotherapy minimally impacts the metabolome and transcriptome of human skeletal muscle

Cryotherapy is commonly used in the treatment of skeletal muscle injuries. However, the data to support the use of cryotherapy is inconclusive, and the biochemical etiology of cryotherapy in human skeletal muscle remains largely unknown. We therefore sought to determine how a clinically-relevant dose of cryotherapy would impact the transcriptome and metabolome of skeletal muscle. Eight healthy male subjects (age 24.7 ± 4.5 years, BMI 22.2 ± 1.6) received a 15 minute bout of local cryotherapy, delivered via ice cup massage over the anterolateral thigh. This resulted in an 85% decrease in skin temperature and a predicted 27% reduction in intramuscular temperature. The contralateral side served as a non-treated control. Two hours after cryotherapy, muscle biopsies were obtained to analyze changes in the transcriptome, metabolome, and activation of p38 MAPK, ERK1/2, Akt, and p70S6K proteins. No changes were detected in the transcriptome between control and cooled muscles. Cryotherapy reduced levels of hexose sugars and hypoxanthine by 1.3%, but no statistically different changes were observed in 60 additional metabolites. Overall, no differences in phosphorylated p38 MAPK, ERK1/2, Akt, and p70S6K were observed. A clinically relevant dose of cryotherapy produced negligible acute biochemical and molecular changes in the skeletal muscle of human subjects.

RNA-binding protein RBM3 prevents NO-induced apoptosis in human neuroblastoma cells by modulating p38 signaling and miR-143

Nitric oxide (NO)-induced apoptosis in neurons is an important cause of neurodegenerative disease in humans. The cold-inducible protein RBM3 mediates the protective effects of cooling on apoptosis induced by various insults. However, whether RBM3 protects neural cells from NO-induced apoptosis is unclear. This study aimed to investigate the neuroprotective effect of RBM3 on NO-induced apoptosis in human SH-SY5Y neuroblastoma cells. Firstly, we demonstrated that mild hypothermia (32 °C) induces RBM3 expression and confers a potent neuroprotective effect on NO-induced apoptosis, which was substantially diminished when RBM3 was silenced by siRNA. Moreover, overexpression of RBM3 exhibited a strong protective effect against NO-induced apoptosis. Signaling pathway screening demonstrated that only p38 inhibition by RBM3 provided neuroprotective effect, although RBM3 overexpression could affect the activation of p38, JNK, ERK, and AKT signaling in response to NO stimuli. Notably, RBM3 overexpression also blocked the activation of p38 signaling induced by transforming growth factor-β1. Furthermore, both RBM3 overexpression and mild hypothermia abolished the induction of miR-143 by NO, which was shown to mediate the cytotoxicity of NO in a p38-dependent way. These findings suggest that RBM3 protects neuroblastoma cells from NO-induced apoptosis by suppressing p38 signaling, which mediates apoptosis through miR-143 induction.

Cold-inducible proteins CIRP and RBM3, a unique couple with activities far beyond the cold

Cold-inducible RNA-binding protein (CIRP) and RNA-binding motif protein 3 (RBM3) are two evolutionarily conserved RNA-binding proteins that are transcriptionally upregulated in response to low temperature. Featuring an RNA-recognition motif (RRM) and an arginine-glycine-rich (RGG) domain, these proteins display many similarities and specific disparities in the regulation of numerous molecular and cellular events. The resistance to serum withdrawal, endoplasmic reticulum stress, or other harsh conditions conferred by RBM3 has led to its reputation as a survival gene. Once CIRP protein is released from cells, it appears to bolster inflammation, contributing to poor prognosis in septic patients. A variety of human tumor specimens have been analyzed for CIRP and RBM3 expression. Surprisingly, RBM3 expression was primarily found to be positively associated with the survival of chemotherapy-treated patients, while CIRP expression was inversely linked to patient survival. In this comprehensive review, we summarize the evolutionary conservation of CIRP and RBM3 across species as well as their molecular interactions, cellular functions, and roles in diverse physiological and pathological processes, including circadian rhythm, inflammation, neural plasticity, stem cell properties, and cancer development.

RNA binding protein RBM3 increases β-catenin signaling to increase stem cell characteristics in colorectal cancer cells

Colorectal cancer (CRC) is the second leading cause of cancer deaths in the United States. It arises from loss of intestinal epithelial homeostasis and hyperproliferation of the crypt epithelium. In order to further understand the pathogenesis of CRC it is important to further understand the factors regulating intestinal epithelial proliferation and more specifically, regulation of the intestinal epithelial stem cell compartment. Here, we investigated the role of the RNA binding protein RBM3 in stem cell homeostasis in colorectal cancers. Using a doxycycline (Dox) inducible RBM3 overexpressing cell lines HCT 116 and DLD-1, we measured changes in side population (SP) cells that have high xenobiotic efflux capacity and increased capacity for self-renewal. In both cell lines, RBM3 induction showed significant increases in the percentage of side population cells. Additionally, we observed increases in spheroid formation and in cells expressing DCLK1, LGR5 and CD44^Hi . As the Wnt/β-catenin signaling pathway is important for both physiologic and cancer stem cells, we next investigated the effects of RBM3 overexpression on β-catenin activity. RBM3 overexpression increased levels of nuclear β-catenin as well as TCF/LEF transcriptional activity. In addition, there was inactivation of GSK3β leading to decreased β-catenin phosphorylation. Pharmacologic inhibition of GSK3β using (2'Z,3'E)-6-Bromoindirubin-3'-oxime (BIO) also recapitulates the RBM3 induced β-catenin activity. In conclusion, we see that RNA binding protein RBM3 induces stemness in colorectal cancer cells through a mechanism involving suppression of GSK3β activity thereby enhancing β-catenin signaling. © 2015 Wiley Periodicals, Inc.

Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training

We investigated functional, morphological and molecular adaptations to strength training exercise and cold water immersion (CWI) through two separate studies. In one study, 21 physically active men strength trained for 12 weeks (2 days per week), with either 10 min of CWI or active recovery (ACT) after each training session. Strength and muscle mass increased more in the ACT group than in the CWI group (P < 0.05). Isokinetic work (19%), type II muscle fibre cross-sectional area (17%) and the number of myonuclei per fibre (26%) increased in the ACT group (all P < 0.05), but not the CWI group. In another study, nine active men performed a bout of single-leg strength exercises on separate days, followed by CWI or ACT. Muscle biopsies were collected before and 2, 24 and 48 h after exercise. The number of satellite cells expressing neural cell adhesion molecule (NCAM) (10-30%) and paired box protein (Pax7) (20-50%) increased 24-48 h after exercise with ACT. The number of NCAM(+) satellite cells increased 48 h after exercise with CWI. NCAM(+) - and Pax7(+) -positive satellite cell numbers were greater after ACT than after CWI (P < 0.05). Phosphorylation of p70S6 kinase(Thr421/Ser424) increased after exercise in both conditions but was greater after ACT (P < 0.05). These data suggest that CWI attenuates the acute changes in satellite cell numbers and activity of kinases that regulate muscle hypertrophy, which may translate to smaller long-term training gains in muscle strength and hypertrophy. The use of CWI as a regular post-exercise recovery strategy should be reconsidered.

Cold stress protein RBM3 responds to temperature change in an ultra-sensitive manner in young neurons

Extremely mild hypothermia to 36.0 °C is not thought to appreciably differ clinically from 37.0 °C. However, it is possible that 36.0 °C stimulates highly sensitive hypothermic signaling mechanism(s) and alters biochemistry. To the best of our knowledge, no such ultra-sensitive pathway/mechanisms have been described. Here we show that cold stress protein RNA binding motif 3 (RBM3) increases in neuron and astrocyte cultures maintained at 33 °C or 36 °C for 24 or 48 h, compared to 37 °C controls. Neurons cultured at 36 °C also had increased global protein synthesis (GPS). Finally, we found that melatonin or fibroblast growth factor 21 (FGF21) augmented RBM3 upregulation in young neurons cooled to 36 °C. Our results show that a 1 °C reduction in temperature can induce pleiotropic biochemical changes by upregulating GPS in neurons which may be mediated by RBM3 and that this process can be pharmacologically mimicked and enhanced with melatonin or FGF21.

Molecular characterization of RNA binding motif protein 3 (RBM3) gene from Pashmina goat

Pashmina goat inhabits the high altitude cold arid desert of Ladakh, India. This goat is known for its finest and costliest under fiber. Though the under fiber may be a part of its complex thermoregulation mechanism, the genetics of its adaptability under cold conditions is not known. As an attempt to understand its adaptive genetics, and the role of RNA-binding proteins at the cellular response, this study was conducted to characterize the RBM3 gene in Pashmina goat and its expression during hypothermia. The ORF of Pashmina RBM3 gene was 273 bp. Phylogenetic analysis revealed that Pashmina RBM3 is closely related to Bos taurus RBM3. Pashmina RBM3 was characterized by comparative modeling studies. The final 3-D model contained two α-helices and four β-sheets. qRT-PCR data showed that Pashmina RBM3 gene expression was significantly higher (P < 0.05) at moderate (30 °C) hypothermic stress conditions as compared with deep (15 °C) hypothermia.

The effects of temperature and seasons on subcutaneous white adipose tissue in humans: evidence for thermogenic gene induction

CONTEXT

Although brown adipose tissue (BAT) activity is increased by a cold environment, little is known of the response of human white adipose tissue (WAT) to the cold.

DESIGN

We examined both abdominal and thigh subcutaneous (SC) WAT from 71 subjects who were biopsied in the summer or winter, and adipose expression was assessed after an acute cold stimulus applied to the thigh of physically active young subjects.

RESULTS

In winter, UCP1 and PGC1α mRNA were increased 4 to 10-fold (p < 0.05) and 1.5 to 2-fold, respectively, along with beige adipose markers, and UCP1 protein was 3-fold higher in the winter. The seasonal increase in abdominal SC WAT UCP1 mRNA was considerably diminished in subjects with a BMI > 30 kg/m(2), suggesting that dysfunctional WAT in obesity inhibits adipose thermogenesis. After applying an acute cold stimulus to the thigh of subjects for 30 min, PGC1α and UCP1 mRNA was stimulated 2.7-fold (p < 0.05) and 1.9-fold (p = 0.07), respectively. Acute cold also induced a 2 to 3-fold increase in PGC1α and UCP1 mRNA in human adipocytes in vitro, which was inhibited by macrophage-conditioned medium and by the addition of TNFα.

CONCLUSION

Human SC WAT increases thermogenic genes seasonally and acutely in response to a cold stimulus and this response is inhibited by obesity and inflammation.

Spatiotemporal pattern of RNA-binding motif protein 3 expression after spinal cord injury in rats

RNA-binding motif protein 3 (RBM3) belongs to a very small group of cold inducible proteins with anti-apoptotic and proliferative functions. To elucidate the expression and possible function of RBM3 in central nervous system (CNS) lesion and repair, we performed a spinal cord injury (SCI) model in adult rats. Western blot analysis revealed that RBM3 level significantly increased at 1 day after damage, and then declined during the following days. Immunohistochemistry further confirmed that RBM3 immunoactivity was expressed at low levels in gray and white matters in normal condition and increased at 1 day after SCI. Besides, double immunofluorescence staining showed RBM3 was primarily expressed in the neurons and a few of astrocytes in the normal group. While after injury, the expression of RBM3 increased both in neurons and astrocytes at 1 day. We also examined the expression profiles of proliferating cell nuclear antigen (PCNA) and active caspase-3 in injured spinal cords by western blot. Importantly, double immunofluorescence staining revealed that cell proliferation evaluated by PCNA appeared in many RBM3-expressing cells and rare caspase-3 was observed in RBM3-expressing cells at 1 day after injury. Our data suggested that RBM3 might play important roles in CNS pathophysiology after SCI.

Stress-response protein RBM3 attenuates the stem-like properties of prostate cancer cells by interfering with CD44 variant splicing

Stress-response pathways play an important role in cancer. The cold-inducible RNA-binding protein RBM3 is upregulated in several types of cancer, including prostate cancer, but its pathogenic contributions are undetermined. RBM3 is expressed at low basal levels in human fetal prostate or in CD133(+) prostate epithelial cells (PrEC), compared with the adult prostate or CD133-PrEC, and RBM3 is downregulated in cells cultured in soft agar or exposed to stress. Notably, RBM3 overexpression in prostate cancer cells attenuated their stem cell-like properties in vitro as well as their tumorigenic potential in vivo. Interestingly, either overexpressing RBM3 or culturing cells at 32°C suppressed RNA splicing of the CD44 variant v8-v10 and increased expression of the standard CD44 (CD44s) isoform. Conversely, silencing RBM3 or culturing cells in soft agar (under conditions that enrich for stem cell-like cells) increased the ratio of CD44v8-v10 to CD44s mRNA. Mechanistic investigations showed that elevating CD44v8-v10 interfered with MMP9-mediated cleavage of CD44s and suppressed expression of cyclin D1, whereas siRNA-mediated silencing of CD44v8-v10 impaired the ability of prostate cancer cells to form colonies in soft agar. Together, these findings suggested that RBM3 contributed to stem cell-like character in prostate cancer by inhibiting CD44v8-v10 splicing. Our work uncovers a hitherto unappreciated role of RBM3 in linking stress-regulated RNA splicing to tumorigenesis, with potential prognostic and therapeutic implications in prostate cancer.

Enhancement of cultured adult motor neuron survival with cold pre-incubation

The aim of the study was to extend the survival of adult spinal motor neurons in serum free culture. Anterior half of the spinal cord was removed from young adult mice and dissociated. Cultured cells attempted to extend neurites within hours of incubation at 37 °C and died within 24 h. To prevent this early regenerative activity, thus to decrease the metabolic requirements of the neurons, cultures were transferred to 4 °C immediately after they were set and kept there for 3 days. Preparations were then taken to 37 °C where they lived up to 8 days. Some neurons continued to extend neurites until the day they died. To understand whether the enhancement of survival involves new protein synthesis, transcription and translation were blocked during cold pre-incubation, which shortened the half life of neurons but not changed the maximum survival period. In conclusion this study has shown that, in the serum-free cultures, the survival of adult spinal motor neurons can be significantly enhanced by cold pre-incubation whose effect seems to depend largely on a reduction in the metabolic activity and less on new protein synthesis.

Preconditioning approach in stem cell therapy for the treatment of infarcted heart

Nearly two decades of research in regenerative medicine have been focused on the development of stem cells as a therapeutic option for treatment of the ischemic heart. Given the ability of stem cells to regenerate the damaged tissue, stem-cell-based therapy is an ideal approach for cardiovascular disorders. Preclinical studies in experimental animal models and clinical trials to determine the safety and efficacy of stem cell therapy have produced encouraging results that promise angiomyogenic repair of the ischemically damaged heart. Despite these promising results, stem cell therapy is still confronted with issues ranging from uncertainty about the as-yet-undetermined "ideal" donor cell type to the nonoptimized cell delivery strategies to harness optimal clinical benefits. Moreover, these lacunae have significantly hampered the progress of the heart cell therapy approach from bench to bedside for routine clinical applications. Massive death of donor cells in the infarcted myocardium during acute phase postengraftment is one of the areas of prime concern, which immensely lowers the efficacy of the procedure. An overview of the published data relevant to stem cell therapy is provided here and the various strategies that have been adopted to develop and optimize the protocols to enhance donor stem cell survival posttransplantation are discussed, with special focus on the preconditioning approach.

Widespread regulation of miRNA biogenesis at the Dicer step by the cold-inducible RNA-binding protein, RBM3

MicroRNAs (miRNAs) play critical roles in diverse cellular events through their effects on translation. Emerging data suggest that modulation of miRNA biogenesis at post-transcriptional steps by RNA-binding proteins is a key point of regulatory control over the expression of some miRNAs and the cellular processes they influence. However, the extent and conditions under which the miRNA pathway is amenable to regulation at posttranscriptional steps are poorly understood. Here we show that RBM3, a cold-inducible, developmentally regulated RNA-binding protein and putative protooncogene, is an essential regulator of miRNA biogenesis. Utilizing miRNA array, Northern blot, and PCR methods, we observed that over 60% of miRNAs detectable in a neuronal cell line were significantly downregulated by knockdown of RBM3. Conversely, for select miRNAs assayed by Northern blot, induction of RBM3 by overexpression or mild hypothermia increased their levels. Changes in miRNA expression were accompanied by changes in the levels of their ~70 nt precursors, whereas primary transcript levels were unaffected. Mechanistic studies revealed that knockdown of RBM3 does not reduce Dicer activity or impede transport of pre-miRNAs into the cytoplasm. Rather, we find that RBM3 binds directly to ~70 nt pre-miRNA intermediates and promotes / de-represses their ability as larger ribonucleoproteins (pre-miRNPs) to associate with active Dicer complexes. Our findings suggest that the processing of a majority of pre-miRNPs by Dicer is subject to an intrinsic inhibitory influence that is overcome by RBM3 expression. RBM3 may thus orchestrate changes in miRNA expression during hypothermia and other cellular stresses, and in the euthermic contexts of early development, differentiation, and oncogenesis where RBM3 expression is highly elevated. Additionally, our data suggest that temperature-dependent changes in miRNA expression mediated by RBM3 may contribute to the therapeutic effects of hypothermia, and are an important variable to consider in in vitro studies of translation-dependent cellular events.