Differential alteration of heat shock protein 90 in mice modifies glucocorticoid receptor function and susceptibility to trauma

Terahertz spectroscopic diagnosis of early blast-induced traumatic brain injury in rats

The early diagnosis of blast-induced traumatic brain injury (bTBI) is of great clinical significance for prognostication and treatment. Here, we report a new strategy for early bTBI diagnosis through serum and cerebrospinal fluid (CSF) based on terahertz time-domain spectroscopy (THz-TDS). The spectral differences of serum and CSF for different degrees of experimental bTBI in rats have been demonstrated in the early period. In addition, the THz spectra of total protein in the hypothalamus and hippocampus were investigated at different time points after blast exposure, which both showed clear differences with time increasing compared with that in the normal brain. This might help to explain the neurological symptoms caused by bTBI. Moreover, based on the THz absorption spectra of serum and CSF, the principal component analysis and machine learning algorithms were performed to automatically identify the degree of bTBI. The highest diagnostic accuracy was up to 95.5%. It is suggested that this method has potential as an alternative method for high-sensitive, rapid, label-free, economical and early diagnosis of bTBI.

Caffeine attenuates brain injury but increases mortality induced by high-intensity blast wave exposure

Caffeine is a substance that is consumed worldwide, and it may exert neuroprotective effects against various cerebral insults, including neurotrauma, which is the most prevalent injury among military personnel. To investigate the effects of caffeine on high-intensity blast wave-induced severe blast injury in mice, three different paradigms of caffeine were applied to male C57BL/6 mice with severe whole body blast injury (WBBI). The results demonstrated that chronic caffeine treatment alleviated blast-induced traumatic brain injury (bTBI); however, both chronic and acute caffeine treatments exacerbated blast-induced lung injuries and, more importantly, increased both the cumulative and time-segmented mortalities postinjury. Interestingly, withdrawing caffeine intake preinjury resulted in favorable outcomes in mortality and lung injury, similar to the findings in water-treated mice, and had the trend to attenuate brain injury. These findings demonstrated that although drinking coffee or caffeine preparations attenuated blast-induced brain trauma, these beverages may place personnel in the battlefield at high risk of casualties, which will help us re-evaluate the therapeutic strategy of caffeine application, particularly in multiple-organ-trauma settings. Furthermore, these findings provided possible strategies for reducing the risk of casualties with caffeine consumption, which may help to change the coffee-drinking habits of military personnel.

Hsp90 regulation affects the treatment of glucocorticoid for pancreatitis-induced lung injury

Glucocorticoids are commonly used for the treatment of pancreatitis and complicated acute lung injury and help to reduce the mortality rates of both. The effect of gene variants in heat shock protein 90 (Hsp90), a key chaperone molecule of the glucocorticoid receptor (GR), on the therapeutic effect of glucocorticoids is unclear. Our study aims to investigate the different susceptibility to glucocorticoid treatment in BALB/c and C57BL/6 mice carrying different Hsp90 genotypes in an animal model of pancreatitis-induced lung injury. Compared with BALB/c mice, C57BL/6 mice have lower mortality rates, decreased water content in their lungs, and a lower level of IL-1 beta in an animal model of acute pancreatitis. C57BL/6 mice show a greater therapeutic effect and increased GR binding activities with glucocorticoid responsive element compared to BALB/c mice after a 0.4 mg/kg dexamethasone (DEX) treatment. Treatment with a higher dose of DEX (4 mg/kg) significantly reduced mortality rates and increased GR-GRE binding activity in both strains of mice, and there was no significant difference between the two strains. DEX did not exert a protective role after geldanamycin, a specific inhibitor of Hsp90, was administered in both strains of mice. Our study revealed that Hsp90 gene variants are responsible for the greater therapeutic effect of DEX in C57BL/6 mice compared to BALB/c mice, which implies that combining DEX treatment with Hsp90 regulation would promote the efficiency of DEX and would be an effective way to alleviate the side effects of hormone therapy.

Blast-induced traumatic brain injury: a new trend of blast injury research

Blast injury has become the major life- and function-threatening injuries in recent warfares. There is increased research interest in the mental disorders caused by blast-induced traumatic brain injury (bTBI), which has been proved as one of the "signature wounds" in modern battlefield. We reviewed the recent progresses in bTBI-related researches and concluded that the new era of blast injury research has shifted from the traditional physical impairments to cognitive dysfunctional/mental disorders that are proved to be more related to the outcome of combat casualty care.

The past and present of blast injury research in China

With the increasing incidence of blast injury, the research on its mechanisms and protective measures draws more and more attention. Blast injury has many characteristics different from general war injuries or trauma. For example, soldiers often have various degrees of visceral injury without significant surface damage, combined injuries and arterial air embolism. Researchers in China began to investigate blast injury later than the United States and Sweden, but the development is so fast that lots of achievements have been gained, including the development of biological shock tube, the mechanisms and characteristics of blast injury in various organs, as well as protective measures under special environments. This article reviews the past and current situation of blast injury research in China.

Enhancement of stress resilience through histone deacetylase 6-mediated regulation of glucocorticoid receptor chaperone dynamics

BACKGROUND

Acetylation of heat shock protein 90 (Hsp90) regulates downstream hormone signaling via the glucocorticoid receptor (GR), but the role of this molecular mechanism in stress homeostasis is poorly understood. We tested whether acetylation of Hsp90 in the brain predicts and modulates the behavioral sequelae of a mouse model of social stress.

METHODS

Mice subjected to chronic social defeat stress were stratified into resilient and vulnerable subpopulations. Hypothalamic-pituitary-adrenal axis function was probed using a dexamethasone/corticotropin-releasing factor test. Measurements of Hsp90 acetylation, Hsp90-GR interactions, and GR translocation were performed in the dorsal raphe nucleus. To manipulate Hsp90 acetylation, we pharmacologically inhibited histone deacetylase 6, a known deacetylase of Hsp90, or overexpressed a point mutant that mimics the hyperacetylated state of Hsp90 at lysine K294.

RESULTS

Lower acetylated Hsp90, higher GR-Hsp90 association, and enhanced GR translocation were observed in dorsal raphe nucleus of vulnerable mice after chronic social defeat stress. Administration of ACY-738, a histone deacetylase 6-selective inhibitor, led to Hsp90 hyperacetylation in brain and in neuronal culture. In cell-based assays, ACY-738 increased the relative association of Hsp90 with FK506 binding protein 51 versus FK506 binding protein 52 and inhibited hormone-induced GR translocation. This effect was replicated by overexpressing the acetylation-mimic point mutant of Hsp90. In vivo, ACY-738 promoted resilience to chronic social defeat stress, and serotonin-selective viral overexpression of the acetylation-mimic mutant of Hsp90 in raphe neurons reproduced the behavioral effect of ACY-738.

CONCLUSIONS

Hyperacetylation of Hsp90 is a predictor and causal molecular determinant of stress resilience in mice. Brain-penetrant histone deacetylase 6 inhibitors increase Hsp90 acetylation and modulate GR chaperone dynamics offering a promising strategy to curtail deleterious socioaffective effects of stress and glucocorticoids.

Adenosine A2A receptor deficiency alleviates blast-induced cognitive dysfunction

Traumatic brain injury (TBI), particularly explosive blast-induced TBI (bTBI), has become the most prevalent injury among military personnel. The disruption of cognitive function is one of the most serious consequences of bTBI because its long-lasting effects prevent survivors fulfilling their active duty and resuming normal civilian life. However, the mechanisms are poorly understood and there is no treatment available. This study investigated the effects of adenosine A2A receptor (A2AR) on bTBI-induced cognitive deficit, and explored the underlying mechanisms. After being subjected to moderate whole-body blast injury, mice lacking the A2AR (A2AR knockout (KO)) showed less severity and shorter duration of impaired spatial reference memory and working memory than wild-type mice did. In addition, bTBI-induced cortical and hippocampal lesions, as well as proinflammatory cytokine expression, glutamate release, edema, cell loss, and gliosis in both early and prolonged phases of the injury, were significantly attenuated in A2AR KO mice. The results suggest that early injury and chronic neuropathological damages are important mechanisms of bTBI-induced cognitive impairment, and that the impairment can be attenuated by preventing A2AR activation. These findings suggest that A2AR antagonism is a potential therapeutic strategy for mild-to-moderate bTBI and consequent cognitive impairment.

The -144C/A polymorphism in the promoter of HSP90beta is associated with multiple organ dysfunction scores

Introduction

Variations in genetic background are the leading cause of differential susceptibility to traumatic infection. Heat shock protein 90 (HSP90), a broadly distributed and conserved molecule, regulates inflammation under stressful and traumatic conditions. However, the relationships between HSP90 genetic polymorphisms, post-traumatic inflammatory responses and organ function remain unknown.

Methods

A total of 286 healthy volunteers and patients with severe trauma took part in a single nucleotide polymorphism (SNP)-based analysis of the HSP90beta gene and a clinical association analysis. HSP90beta and TNF-alpha levels were determined using quantitative PCR and western blot. The transcriptional activity of the HSP90beta promoter was assayed using the Dual-Luciferase Reporter Assay System.

Results

The minor allele frequencies for the SNP located at −144 bp relative to the HSP90beta transcriptional start site were 28.47% and 28.52% in the normal and trauma populations, respectively; no significant differences were found between these two distributions. However, the results showed that a promoter containing the -144A allele had a higher transcriptional activity than did a promoter containing the wild-type -144C allele. Furthermore, the -144A promoter induced high expression of HSP90beta and low expression of the inflammatory factor TNF-alpha in a lipopolysaccharide-induced inflammatory model. A clinical association analysis showed that the multiple organ dysfunction scores for -144AA genotype carriers were significantly lower than those of -144CC carriers following trauma. No significant correlations were found between the presence of the two alleles and the incidence of sepsis.

Conclusions

These results indicate that differences in expression caused by the -144 polymorphism in the HSP90beta promoter are associated with cellular inflammatory responses and the severity of organ injury. These findings will aid in risk assessment and early prevention of complications for patients with severe trauma.