Time-dependent changes in caspase-3 activity and heat shock protein 25 after spinal cord transection in adult rats

A Network Pharmacology to Explore the Mechanism of Calculus Bovis in the Treatment of Ischemic Stroke

BACKGROUND

Calculus Bovis is a valuable Chinese medicine, which is widely used in the clinical treatment of ischemic stroke. The present study is aimed at investigating its target and the mechanism involved in ischemic stroke treatment by network pharmacology.

METHODS

Effective compounds of Calculus Bovis were collected using methods of network pharmacology and using the Bioinformatics Analysis Tool for Molecular Mechanism of Traditional Chinese Medicine (BATMAN-TCM) and the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP). Potential compound targets were searched in the TCMSP and SwissTargetPrediction databases. Ischemic stroke-related disease targets were searched in the Drugbank, DisGeNet, OMIM, and TTD databases. These two types of targets were uploaded to the STRING database, and a network of their interaction (PPI) was built with its characteristics calculated, aiming to reveal a number of key targets. Hub genes were selected using a plug-in of the Cytoscape software, and Gene Ontology (GO) biological processes and pathway enrichment analyses of Kyoto Encyclopedia of Genes and Genomes (KEGG) were conducted using the clusterProfiler package of R language.

RESULTS

Among 12 compounds, deoxycorticosterone, methyl cholate, and biliverdin were potentially effective components. A total of 344 Calculus Bovis compound targets and 590 ischemic stroke targets were found with 92 overlapping targets, including hub genes such as TP53, AKT, PIK2CA, MAPK3, MMP9, and MMP2. Biological functions of Calculus Bovis are associated with protein hydrolyzation, phosphorylation of serine/threonine residues of protein substrates, peptide bond hydrolyzation of peptides and proteins, hydrolyzation of intracellular second messengers, antioxidation and reduction, RNA transcription, and other biological processes.

CONCLUSION

Calculus Bovis may play a role in ischemic stroke by activating PI3K-AKT and MAPK signaling pathways, which are involved in regulating inflammatory response, cell apoptosis, and proliferation.

Key Glycolytic Metabolites in Paralyzed Skeletal Muscle Are Altered Seven Days after Spinal Cord Injury in Mice

Spinal cord injury (SCI) results in rapid muscle atrophy and an oxidative-to-glycolytic fiber-type shift. Those with chronic SCI are more at risk for developing insulin resistance and reductions in glucose clearance than able-bodied individuals, but how glucose metabolism is affected after SCI is not well known. An untargeted metabolomics approach was utilized to investigate changes in whole-muscle metabolites at an acute (7-day) and subacute (28-day) time frame after a complete T9 spinal cord transection in 20-week-old female C57BL/6 mice. Two hundred one metabolites were detected in all samples, and 83 had BinBase IDs. A principal components analysis showed the 7-day group as a unique cluster. Further, 36 metabolites were altered after 7- and/or 28-day post-SCI (p values <0.05), with 12 passing further false discovery rate exclusion criteria; of those 12 metabolites, three important glycolytic molecules-glucose and downstream metabolites pyruvic acid and lactic acid-were reduced at 7 days compared to those values in sham and/or 28-day animals. These changes were associated with altered expression of proteins associated with glycolysis, as well as monocarboxylate transporter 4 gene expression. Taken together, our data suggest an acute disruption of skeletal muscle glucose uptake at 7 days post-SCI, which leads to reduced pyruvate and lactate levels. These levels recover by 28 days post-SCI, but a reduction in pyruvate dehydrogenase protein expression at 28 days post-SCI implies disruption in downstream oxidation of glucose.

Salvianolic acid B protects the myelin sheath around injured spinal cord axons

Salvianolic acid B, an active pharmaceutical compound present in Salvia miltiorrhiza, exerts a neuroprotective effect in animal models of brain and spinal cord injury. Salvianolic acid B can promote recovery of neurological function; however, its protective effect on the myelin sheath after spinal cord injury remains poorly understood. Thus, in this study, in vitro tests showed that salvianolic acid B contributed to oligodendrocyte precursor cell differentiation, and the most effective dose was 20 μg/mL. For in vivo investigation, rats with spinal cord injury were intraperitoneally injected with 20 mg/kg salvianolic acid B for 8 weeks. The amount of myelin sheath and the number of regenerating axons increased, neurological function recovered, and caspase-3 expression was decreased in the spinal cord of salvianolic acid B-treated animals compared with untreated control rats. These results indicate that salvianolic acid B can protect axons and the myelin sheath, and can promote the recovery of neurological function. Its mechanism of action is likely to be associated with inhibiting apoptosis and promoting the differentiation and maturation of oligodendrocyte precursor cells.

Focal adhesion kinase signaling is decreased 56 days following spinal cord injury in rat gastrocnemius

STUDY DESIGN

Descriptive study.

OBJECTIVES

The goal of this study was to determine the effects of spinal cord injury (SCI) on aspects of the focal adhesion kinase (FAK) signaling pathway 56 days post injury in rat gastrocnemius.

SETTING

This study was conducted in Bronx, NY, USA.

METHODS

Three-month-old male Wistar rats were exposed to either a sham surgery (n=10) or complete T4 spinal cord transection (n=10). Rats were killed 56 days following surgery and the muscle was collected. Following homogenization, proteins of the FAK pathway were analyzed by western immunoblotting or reverse transcription-qPCR. In addition, cellular markers for proteins that target the degradation of FAK were investigated.

RESULTS

SCI resulted in significantly lower levels of total and phosphorylated FAK, cSrc and p70S6k, and a trend for increased FRNK protein expression. SCI did not change levels of the α7 or β1 integrin subunits, total or phosphorylated ERK1/2, phosphorylated Akt and TSC2 or total p70S6k. SCI resulted in a greater expression of total Akt. mRNA expression of FAK and the α7 or β1 integrins remained unchanged between sham and SCI groups. Caspase-3/7 activity and Trim72 mRNA and protein expression remained unchanged following SCI.

CONCLUSION

SCI results in diminished FAK signaling and is independent of ERK1/2 and Akt. SCI has no effect on mRNA levels for genes encoding components of the focal adhesion 56 days after injury.

Effect of HSP25 loss on muscle contractile function and running wheel activity in young and old mice

Aging is associated with an adverse decline in muscle function, often manifesting as decreased strength and increased muscle fatigability that negatively affects the overall health of the elderly. Heat shock proteins (HSPs), a family of stress inducible proteins known to protect cells from damage, are highly induced in muscle cells following exercise, but both basal and inducible levels decline with age. Utilizing young and old mice lacking HSP25 (Hsp25^−/−) we tested the hypothesis that HSP25 is required to maintain normal muscle function and that age related decreases in HSP25 directly contribute to declining muscle function. Running wheel distances over 14 days for young Hsp25^−/− mice were significantly lower than for the corresponding Hsp25^+/+ genotype (81238 vs. 33956 AUC, respectively). While older groups both ran significantly less than young groups, in aged mice HSP25 loss did not lead to any additional decrease. Significantly lower myofibrillar (contractile) protein levels in young Hsp25^−/− vs. Hsp25^+/+ (15.7 ± 0.2 vs. 13.4 ± 0.3 mg/mg muscle) mice suggests HSP25 loss was associated with greater muscle breakdown during voluntary wheel running. In vivo, plantarflexor maximal isometric force was significantly decreased in aged vs. young mice, but the loss of HSP25 had no effect on either group. However, plantarflexor fatigability over 10 contractions was significantly higher in young Hsp25^−/− vs. Hsp25^+/+ mice (59 ± 3 vs. 49 ± 4% of initial force, respectively) but no similar effect of genotype was detected in the older groups. There was no difference in muscle caspase-3 activity between Hsp25^−/− and Hsp25^{+/+ mice}, whether young or old, but there was a significant genotype independent increase in activity with age. Overall, the results suggest that the absence of HSP25 primarily contributes to muscle fatigue resistance, rather than maximal force production, and that this effect is most evident in young compared to older mice.

Effects of glutamine supplementation on muscle function and stress responses in a mouse model of spinal cord injury

Spinal cord injury (SCI) results in loss of muscle function due to rapid breakdown of contractile proteins. Glutamine supplementation improves clinical outcomes, but its effects on muscle function after SCI are unknown. The benefits of glutamine in non-skeletal muscle tissues involve elevated heat shock protein (Hsp)70 and Hsp25, but the muscle response may differ because it is the largest contributor to plasma glutamine. We tested the hypothesis that glutamine preserves muscle function after SCI and that this is associated with increased heat shock protein and reduced inflammatory factors, interleukin-6 (IL-6) and tumour necrosis factor-α (TNFα). Changes in plantarflexor force, fatigability and total myofibrillar, Hsp70, Hsp25, IL-6 and TNFα muscle protein levels were measured 7 days after sham or spinal cord transection surgery in mice receiving daily placebo or glutamine. Compared with placebo, after SCI glutamine significantly attenuated the reductions in maximal isometric force (0.22 ± 0.01 versus 0.31 ± 0.03 N, respectively) and fatigue resistance (34 ± 4 versus 59 ± 4% of initial force, respectively). Glutamine significantly ameliorated the loss of myofibrillar protein with spinal cord transection. Spinal cord transection was associated with decreased Hsp70 and Hsp25 with glutamine only (45 ± 3 and 44 ± 5% of placebo, respectively). Glutamine significantly reduced spinal cord transection-associated increases in IL-6 and TNFα compared with placebo (38 ± 6 and 37 ± 8% of placebo, respectively). Functionally, early reductions in contractile protein, force and fatigue resistance after SCI were reversed with glutamine. Spinal cord transection-associated reductions in Hsp70, Hsp25, IL-6 and TNFα with glutamine versus placebo suggest lower stress in the muscle, possibly related to a reduced need to produce glutamine. These findings support glutamine as a therapeutic intervention to accelerate recovery of muscle function after SCI.

HSP25 can modulate myofibrillar desmin cytoskeleton following the phosphorylation at Ser15 in rat soleus muscle

The main purpose of the present study was to investigate the role(s) of 25-kDa heat shock protein (HSP25) in the regulation and integration of myofibrillar Z-disc structure during down- or upregulation of the size in rat soleus muscle fibers. Hindlimb unloading by tail suspension was performed in adult rats for 7 days, and reloading was allowed for 5 days after the termination of suspension. Interaction of HSP25 and Z-disc proteins, phosphorylation status, distribution, and complex formation of HSP25 were investigated. Non- and single-phosphorylated HSP25s were generally expressed in the cytoplasmic fraction of normal muscle. The level of total HSP25, as well as the phosphorylation ratio, did not change significantly in response to atrophy. Increased expressions of HSP25, phosphorylated at serine 15 (p-Ser15) and dual-phosphorylated form, were noted, when atrophied muscles were reloaded. Myofibrillar HSP25 was also noted in reloaded muscle. Histochemical analysis further indicated the localization of p-Ser15 in the regions with disorganization of Z-disc structure in reloaded muscle fibers. HSP25 formed a large molecular complex in the cytoplasmic fraction of normal muscle, whereas dissociation of free HSP25 with Ser15 phosphorylation was noted in reloaded muscle. The interaction of p-Ser15 with desmin and actinin was detected in Z-discs by proximity ligation assay. Strong interaction between p-Ser15 and desmin, but not actinin, was noted in the disorganized areas. These results indicated that HSP25 contributed to the desmin cytoskeletal organization following the phosphorylation at Ser15 during reloading and regrowing of soleus muscle.

Early response of heat shock proteins to functional overload of the soleus and plantaris in rats and mice

Heat shock proteins (HSPs) are important factors in the response of skeletal muscles to chronic increases or decreases in activation and loading. The purpose of this study was to compare species-, time- and muscle-dependent changes in protein expression of Hsp20, Hsp25, αB-crystallin, Hsp72 and Hsp90 in response to functional overload (FO) in rats and mice. We compared protein levels of Hsp20, Hsp25, αB-crystallin, Hsp72 and Hsp90 in soleus and plantaris in baseline conditions and following 0.5, 1, 2, 3 and 7 days (rats) or 3 and 7 days (mice) of FO. Baseline levels of all HSPs were higher in rat soleus than plantaris, whereas only baseline expression of Hsp20 was higher in mouse soleus than plantaris. Levels of Hsp72 and Hsp90 were higher in plantaris and soleus of FO than control mice and rats after 3 and 7 days of FO. Protein levels and phosphorylation of Hsp25 in mouse plantaris and soleus were higher than control levels after 3 and 7 days of FO, except for soleus at 3 days. αB-crystallin levels were higher in plantaris of FO than control mice after 3 and 7 days of FO and in FO than control rats after 7 days of FO. Heat shock protein 20 was the least responsive, increasing only in 7 day FO rat plantaris compared with control rats. Overall, the results demonstrate that levels of both large and small HSPs increase with FO, suggesting a contributory role during the compensatory hypertrophy response.

Hsp27 inhibits IKKbeta-induced NF-kappaB activity and skeletal muscle atrophy

Heat shock protein 25/27 (Hsp25/27) is a cytoprotective protein that is ubiquitously expressed in most cells, and is up-regulated in response to cellular stress. Previous work, in nonmuscle cells, has shown that Hsp27 inhibits TNF-alpha-induced NF-kappaB activation. During skeletal muscle disuse, Hsp25/27 levels are decreased and NF-kappaB activity increased, and this increase in NF-kappaB activity is required for disuse muscle atrophy. Therefore, the purpose of the current study was to determine whether electrotransfer of Hsp27 into the soleus muscle of rats, prior to skeletal muscle disuse, is sufficient to inhibit skeletal muscle disuse atrophy and NF-kappaB activation. The 35% disuse muscle-fiber atrophy observed in nontransfected fibers was attenuated by 50% in fibers transfected with Hsp27. Hsp27 also inhibited the disuse-induced increase in MuRF1 and atrogin-1 transcription by 82 and 40%, respectively. Furthermore, disuse- and IKKbeta-induced NF-kappaB transactivation were abolished by Hsp27. In contrast, Hsp27 had no effect on Foxo transactivation. In conclusion, Hsp27 is a negative regulator of NF-kappaB in skeletal muscle, in vivo, and is sufficient to inhibit MuRF1 and atrogin-1 and attenuate skeletal muscle disuse atrophy.

The role of heat shock proteins in spinal cord injury

Heat shock proteins (HSPs) are normal intracellular proteins that are produced in greater amounts when cells are subjected to stress or injury. These proteins have been shown to play a key role in the modulation of the secondary injury that occurs after the initial spinal cord injury (SCI). Heat shock proteins normally act as molecular chaperones and are called protein guardians because they act to repair partially damaged proteins. Normally intracellular, HSPs can also be liberated into the systemic circulation to act as important inflammatory mediators. In the setting of SCI, HSP induction has been shown to be beneficial. These proteins are liberated primarily by acutely stressed microglial, endothelial, and ependymal cells. Heat shock proteins have also been shown to assist in the protection of motor neurons and to prevent chronic inflammation after SCI. In animal models, several experimental drugs have shown neuroprotective effects in the spinal cord and appear to function by modulating HSPs.

Skeletal muscle dysfunction in patients with chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a debilitating disease characterized by inflammation-induced airflow limitation and parenchymal destruction. In addition to pulmonary manifestations, patients with COPD develop systemic problems, including skeletal muscle and other organ-specific dysfunctions, nutritional abnormalities, weight loss, and adverse psychological responses. Patients with COPD often complain of dyspnea on exertion, reduced exercise capacity, and develop a progressive decline in lung function with increasing age. These symptoms have been attributed to increases in the work of breathing and in impairments in gas exchange that result from airflow limitation and dynamic hyperinflation. However, there is mounting evidence to suggest that skeletal muscle dysfunction, independent of lung function, contributes significantly to reduced exercise capacity and poor quality of life in these patients. Limb and ventilatory skeletal muscle dysfunction in COPD patients has been attributed to a myriad of factors, including the presence of low grade systemic inflammatory processes, nutritional depletion, corticosteroid medications, chronic inactivity, age, hypoxemia, smoking, oxidative and nitrosative stresses, protein degradation and changes in vascular density. This review briefly summarizes the contribution of these factors to overall skeletal muscle dysfunction in patients with COPD, with particular attention paid to the latest advances in the field.