The expression and changes of heat shock protein 70, MDA and haemorheology in rat cortex after diffuse axonal injury with secondary insults

Establishment of a model to predict mortality after decompression craniotomy for traumatic brain injury

BACKGROUND

The mortality rate of patients with traumatic brain injury (TBI) is still high even while undergoing decompressive craniectomy (DC), and the expensive treatment costs bring huge economic burden to the families of patients.

OBJECTIVE

The aim of this study was to identify preoperative indicators that influence patient outcomes and to develop a risk model for predicting patient mortality by a retrospective analysis of TBI patients undergoing DC.

METHODS

A total of 288 TBI patients treated with DC, admitted to the First Affiliated Hospital of Shantou University Medical School from August 2015 to April 2021, were used for univariate and multivariate logistic regression analysis to determine the risk factors for death after DC in TBI patients. We also built a risk model for the identified risk factors and conducted internal verification and model evaluation.

RESULTS

Univariate and multivariate logistic regression analysis identified four risk factors: Glasgow Coma Scale, age, activated partial thrombin time, and mean CT value of the superior sagittal sinus. These risk factors can be obtained before DC. In addition, we also developed a 3-month mortality risk model and conducted a bootstrap 1000 resampling internal validation, with C-indices of 0.852 and 0.845, respectively.

CONCLUSIONS

We developed a risk model that has clinical significance for the early identification of patients who will still die after DC. Interestingly, we also identified a new early risk factor for TBI patients after DC, that is, preoperative mean CT value of the superior sagittal sinus (p < .05).

Expression of inducible heat shock proteins Hsp27 and Hsp70 in the visual pathway of rats subjected to various models of retinal ganglion cell injury

Inducible heat shock proteins (Hsps) are upregulated in the central nervous system in response to a wide variety of injuries. Surprisingly, however, no coherent picture has emerged regarding the magnitude, duration and cellular distribution of inducible Hsps in the visual system following injury to retinal ganglion cells (RGCs). The current study sought, therefore, to achieve the following two objectives. The first aim of this study was to systematically characterise the patterns of Hsp27 and −70 expression in the retina and optic nerve in four discrete models of retinal ganglion cell (RGC) degeneration: axonal injury (ON crush), somato-dendritic injury (NMDA-induced excitotoxicity), chronic hypoperfusion (bilateral occlusion of the carotid arteris) and experimental glaucoma. The second aim was to document Hsp27 and −70 expression in the optic tract, the subcortical retinorecipient areas of the brain, and the visual cortex during Wallerian degeneration of RGC axons. Hsp27 was robustly upregulated in the retina in each injury paradigm, with the chronic models, 2VO and experimental glaucoma, displaying a more persistent Hsp27 transcriptional response than the acute models. Hsp27 expression was always associated with astrocytes and with a subset of RGCs in each of the models excluding NMDA. Hsp27 was present within astrocytes of the optic nerve/optic tract in control rats. During Wallerian degeneration, Hsp27 was upregulated in the optic nerve/optic tract and expressed de novo by astrocytes in the lateral geniculate nucleus and the stratum opticum of the superior colliculus. Conversely, the results of our study indicate Hsp70 was minimally induced in any of the models of injury, either in the retina, or in the optic nerve/optic tract, or in the subcortical, retinorecipient areas of the brain. The findings of the present study augment our understanding of the involvement of Hsp27 and Hsp70 in the response of the visual system to RGC degeneration.

Anti-hypoxia effect of adenovirus-mediated expression of heat shock protein 70 (HSP70) on primary cultured neurons

Heat shock protein 70 (HSP70) has attracted great attention recently in hypoxia injury because of its close link to the recovery after hypoxic-ischemic damage in organs. However, the cellular mechanism underlying its protective roles remains unclear. In this study, we developed a recombinant adenovirus containing HSP70-GFP (vAd-HSP70-GFP) and studied the effect of virus-mediated expression of exogenous HSP70 gene on neurons in response to hypoxia-reoxygenation injury. Virus-mediated expression of HSP70 was detected as early as 24 hr and lasted until 10 days after infection. Neurons with 48 hr vAd-HSP70-GFP infection were exposed to 0, 0.5, 1, 2, 3, or 4 hr hypoxia followed by 1 hr reoxygenation. The mRNA and protein levels of HSP70 in neurons exposed to different lengths of hypoxia were compared by using RT-PCR and Western blotting (WB). The 1-hr hypoxia exposure showed the most significant increases in the HSP70 mRNA and protein level compared with other exposure durations. MTT assay showed that HSP70 overexpression significantly increased the neuronal viability, accompanied by decreased lactate dehydrogenase (LDH) activity in the culture medium after hypoxia-reoxygenation. Neurons with vAd-HSP70-GFP exhibited increased levels of mitochondrial cytochrome C (Cyt-C) and decreased levels of cytoplasmic Cyt-C compared with vAd-GFP-infected cells. These results suggest a neuroprotective role of exogenous HSP70 against hypoxia-reoxygenation injury, possibly via preventing initiation of mitochondrial apoptosis.

Changes of mGluR4 and the effects of its specific agonist L-AP4 in a rodent model of diffuse brain injury

OBJECTIVE

Excessive release of glutamate from nerve terminals following diffuse brain injury (DBI) is thought to contribute to neuronal calcium overload leading to calcium-mediated cell damage. Metabotropic glutamate receptor subtype 4 (mGluR4) is regarded as one of the neuroprotective receptors in mammalian brains. Therefore, the mGluR4 specific agonists might exert neuroprotective effects after DBI. The focus of this study is to examine the changes of expression of mGluR4 after DBI and the role of its specific agonist L-AP4 in vivo.

METHODS

One hundred and sixty-one male SD rats were randomized into two groups. Group A included normal control, sham-operated control and DBI group. DBI was produced by Marmarou's diffuse head injury model. The mRNA expression of mGluR4 was detected by hybridization in situ. Group B included DBI alone, DBI treated with normal saline and DBI treated with L-AP4. All DBI rats were trained in a series of performance tests, following which they were subjected to DBI. At 1 and 12 h, animals were injected intracerebroventricularly with L-AP4 (100 mM, 10 microl) or normal saline, respectively. The rats were tested for motor and cognitive performance at 1, 3, 7, 14 days post-injury and the damaged neurons were detected.

RESULTS

There was no significant difference between the normal control group and sham-operated group in the expression of mGluR4 (P>0.05). The animals exposed to DBI showed a significant increased expression of mRNA of mGluR4 compared with that of the sham-operated animals 1 h after injuries (P<0.05). At 6 h, the evolution of neuronal expression of mGluR4 in the trauma alone group was relatively static. Compared with saline-treated control animals, rats treated with L-AP4 showed decreased number of damaged neurons and a better motor and cognitive performance.

CONCLUSIONS

The increased expression of mGluR4 is an important process in the pathophysiological of DBI and its specific agonist L-AP4 can provide a remarkable neuroprotection against DBI not only at the histopathological level but also in the motor and cognitive performance.

Metabotropic glutamate receptor antagonists and agonists: potential neuroprotectors in diffuse brain injury

Our previous study has suggested that metabotropic glutamate receptors (mGluRs) were significantly involved in the secondary processes after diffuse brain injury (DBI) and that mGluRs antagonists or agonists may be used for the treatment of DBI. In the present study, the neuroprotective effects of antagonists or agonists of mGluRs on DBI were further investigated. Sprague-Dawly rats were randomized into the following six groups: (i) normal control; (ii) sham-operated control; (iii) DBI; (iv) DBI treated with normal saline (NS); (v) DBI treated with alpha-methyl-4-carboxy-phenylglycine (MCPG); and (vi) DBI treated with (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV). Animals were injected intracerebroventricularly (icv) with 10 microL MCPG (100mmol/L), DCG-IV (10nmol/L) or the equivalent volume of normal saline 1 h after injury. The neurological severity score (NSS), brain water content and the number of damaged neurons were determined 6, 12, 24, 72 and 168 h after injury. In rats with DBI, it was found that the NSS was improved and the water content in the frontal cortex and the number of damaged neurons in the parietal cortex were significantly reduced following icv injection of either MCPG or DCG-IV. This suggests that icv injection of the mGluR group I antagonist MCPG or the mGluR group II agonist DCG-IV may exert neuroprotective effects in the early stage after DBI.

Stress response in rat brain after different durations of noise exposure

The alteration in the levels of plasma corticosterone, brain norepinephrine (NE), and expression of brain heat shock proteins (Hsp70) after different durations of noise exposure (acute, 1 day; sub-acute, 15 days; chronic, 30 days) has been studied to analyze their role in combating time-dependent stress effects of noise. Broadband white noise (100dB) exposure to male Wistar albino rats significantly increased the levels of plasma corticosterone and NE in all three durations of noise exposure. The sustained increase observed in their levels in the chronic group suggests that animals are not getting adapted to noise even after 30 days of exposure. The important role of Hsp70 in combating noise induced stress is evident from the significant increase in its expression after chronic exposure, while there was a reciprocal decrease in the NE and corticosterone when compared with their levels after acute and sub-acute noise exposure. This clearly indicates that the time-dependent stress response to noise exposure is a complex mechanism involving highly interconnected systems such as hypothalamo-pituitary-adrenal (HPA) axis, heat shock proteins and may have serious implications in vital organs, particularly in the brain when there is a prolonged noise exposure.

Secondary insults and outcomes in patients with hypertensive basal ganglia hemorrhage

This study was designed to monitor secondary insults and their impact on outcomes of patients with hypertensive basal ganglia hemorrhage (HBGH). One hundred and twelve patients with HBGH (male 73, female 39) of age 42 +/- 8 years (range from 38 to 57 years) were studied. Operations included craniotomy or trephination drainage with urokinase thrombolysis. Conventional therapies were also given to the patients including the administration of mannitol, crystalloid and colloid solution. In the meantime, blood pressure (MAP), temperature (T) and SaO2 and other parameters were recorded in the intensive care unit. The ICP values were recorded, and the early clinical outcome was assessed upon discharge according to Glasgow Outcome Scale. Cerebral Perfusion Pressure was calculated as CPP = MAP-MICP. Outcomes in the group without secondary insults were better than that in the group with secondary insults (P < 0.01). No unfavorable outcomes were found in the 59 cases managed by ultra-early surgery whereas 36.1% of the cases operated after 6 hours of onset had unfavorable outcomes. It is concluded that the high incident rate of secondary insults in HICH patients influences outcome. Ultra-early surgery may also contribute to improved quality of survival.

A review of heat shock protein induction following cerebellar injury

Exposure of cells to stressful environments such as heat shock, ischemia, trauma and disease, induces the cellular expression of heat shock proteins (Hsps). Since the discovery of heat shock proteins in the early 1960s, efforts to understand their function in both stressed and non-stressed cells have remained the focus of a vast collection of researchers. Post-injury heat shock protein induction is believed to identify regions of reversible cell injury as well as contribute to repair and protective mechanisms following stress. With the role of cerebellum expanding to include a number of cognitive processes in addition to contributing to motor coordination, research contributions that further our understanding of cerebellar repair strategies following injury are significant. Following cellular stress, heat shock protein expression was observed in both neuronal and glial cell populations in the injured cerebellum. Specifically, Hsp27 expression was localized primarily in Purkinje cells and glial cells within the injured cerebellum, whereas Hsp72 induction was more prominent in the granule cell layer of the cerebellum. Thus, there appears to be a preferential expression of different families of heat shock proteins in different cell populations in the injured cerebellum. There are also distinct post-injury time frames of induction for each family of heat shock protein, emphasizing differences in cellular functional requirements for each family of heat shock protein. Hsp27 was expressed immediately following injury and continued up to 20 days post-injury whereas Hsp72 was expressed immediately following injury and disappeared by 4 days post-injury, suggesting the latter contributes to processes involved in the initial repair of injured cells. This review discusses heat shock protein induction patterns in both in vivo and in vitro cerebellar injury models and provides suggestions as to the functional role of heat shock proteins in the injured cerebellum.