Mitochondrial Dysfunction and Apoptosis in Brain Microvascular Endothelial Cells Following Blast Traumatic Brain Injury.

Blood brain barrier (BBB) breakdown is a key driver of traumatic brain injury (TBI), contributing to prolonged neurological deficits and increased risk of death in TBI patients. Strikingly, the role of endothelium in the progression of BBB breakdown has not been sufficiently investigated, even though it constitutes the bulk of BBB structure. In the current study, we investigate TBI-induced changes in the brain endothelium at the subcellular level, particularly focusing on mitochondrial dysfunction, using a combination of confocal imaging, gene expression analysis, and molecular profiling by Raman spectrometry. Herein, we developed and applied an in-vitro blast-TBI (bTBI) model that employs an acoustic shock tube to deliver injury to cultured human brain microvascular endothelial cells (HBMVEC). We found that this injury results in aberrant expression of mitochondrial genes, as well as cytokines/ inflammasomes, and regulators of apoptosis. Furthermore, injured cells exhibit a significant increase in reactive oxygen species (ROS) and in Ca2+ levels. These changes are accompanied by overall reduction of intracellular proteins levels as well as profound transformations in mitochondrial proteome and lipidome. Finally, blast injury leads to a reduction in HBMVEC cell viability, with up to 50% of cells exhibiting signs of apoptosis following 24 h after injury. These findings led us to hypothesize that mitochondrial dysfunction in HBMVEC is a key component of BBB breakdown and TBI progression.

Aberrant Brain Triple-Network Effective Connectivity Patterns in Type 2 Diabetes Mellitus.

INTRODUCTION: Aberrant brain functional connectivity network is thought to be related to cognitive impairment in patients with type 2 diabetes mellitus (T2DM). This study aims to investigate the triple-network effective connectivity patterns in patients with T2DM within and between the default mode network (DMN), salience network (SN), and executive control network (ECN) and their associations with cognitive declines. METHODS: In total, 92 patients with T2DM and 98 matched healthy controls (HCs) were recruited and underwent resting-state functional magnetic resonance imaging (rs-fMRI). Spectral dynamic causal modeling (spDCM) was used for effective connectivity analysis within the triple network. The posterior cingulate cortex (PCC), medial prefrontal cortex (mPFC), lateral prefrontal cortex (LPFC), supramarginal gyrus (SMG), and anterior insula (AINS) were selected as the regions of interest. Group comparisons were performed for effective connectivity calculated using the fully connected model, and the relationships between effective connectivity alterations and cognitive impairment as well as clinical parameters were detected. RESULTS: Compared to HCs, patients with T2DM exhibited increased or decreased effective connectivity patterns within the triple network. Furthermore, diabetes duration was significantly negatively correlated with increased effective connectivity from the r-LPFC to the mPFC, while body mass index (BMI) was significantly positively correlated with increased effective connectivity from the l-LPFC to the l-AINS (r = - 0.353, p = 0.001; r = 0.377, p = 0.004). CONCLUSION: These results indicate abnormal effective connectivity patterns within the triple network model in patients with T2DM and provide new insight into the neurological mechanisms of T2DM and related cognitive dysfunction.

The Influence of Motoric Maneuvers on Cervical Vestibular Evoked Myogenic Potentials (cVEMPs).

BACKGROUND: The cervical vestibular evoked myogenic potential (cVEMP) is a vestibular response that is produced by the saccule in response to intense, often low-frequency, short-duration auditory stimuli, and is typically recorded from a contracted sternocleidomastoid (SCM) muscle. Previous research has shown that the amplitude of the cVEMP is related to the amount of SCM electromyographic (EMG) activity. PURPOSE: The aim of this study was to determine the influence of various remote motoric maneuvers on the amplitude of the cVEMP, as well as whether they influence the level of SCM EMG activity. RESEARCH DESIGN: The cVEMP was recorded from the left SCM muscle to left ear stimulation, in response to the SCM condition, as well as three different motoric maneuvers (jaw clench, eye closure, and the Jendrassik maneuver). EMG activity was also varied between 50, 75, and 100% of maximal EMG activity. STUDY SAMPLE: Data from 14 healthy subjects, with a mean age of 25.57 years (standard deviation = 5.93 years), was included in the present study. DATA COLLECTION AND ANALYSIS: Mean latency and amplitude of the cVEMP were compared across the four conditions and varying magnitudes of EMG contraction. SPSS 26 was used to statistically analyze the results. RESULTS: cVEMP latency did not vary across condition. cVEMP amplitude decreased with decreasing EMG magnitude. SCM contraction with jaw clench produced the largest increase in cVEMP amplitude; however, this condition was not significantly different from the SCM condition alone. SCM contraction with the Jendrassik maneuver produced a cVEMP amplitude that was similar and not statistically different from SCM contraction alone, and the addition of the eye closure maneuver to SCM contraction resulted in the lowest cVEMP amplitude, which was found to be statistically different from the standard SCM condition at 100 and 75% EMG activity. The amplitude relationship across the conditions was not found to vary with changes in EMG activity; however, a significant increase in EMG amplitude was found during the 50% muscle contraction condition when subjects performed the Jendrassik maneuver in addition to the standard SCM contraction. CONCLUSIONS: The addition of the eye closure maneuver to SCM contraction resulted in a significant decrease in cVEMP amplitude, while the addition of the Jendrassik maneuver resulted in a significant increase in EMG activity at the lowest level of SCM activation (i.e., 50%). Additional research is necessary to determine how motoric maneuvers influence the cVEMP amplitude, and whether the results are also dependent on how SCM contraction is being produced (e.g., while supine vs. sitting).

Cross-species experiments reveal widespread cochlear neural damage in normal hearing.

Animal models suggest that cochlear afferent nerve endings may be more vulnerable than sensory hair cells to damage from acoustic overexposure and aging. Because neural degeneration without hair-cell loss cannot be detected in standard clinical audiometry, whether such damage occurs in humans is hotly debated. Here, we address this debate through co-ordinated experiments in at-risk humans and a wild-type chinchilla model. Cochlear neuropathy leads to large and sustained reductions of the wideband middle-ear muscle reflex in chinchillas. Analogously, human wideband reflex measures revealed distinct damage patterns in middle age, and in young individuals with histories of high acoustic exposure. Analysis of an independent large public dataset and additional measurements using clinical equipment corroborated the patterns revealed by our targeted cross-species experiments. Taken together, our results suggest that cochlear neural damage is widespread even in populations with clinically normal hearing.

Blast-induced injury responsive relative gene expression of traumatic brain injury biomarkers in human brain microvascular endothelial cells.

Disruption of the blood-brain barrier (BBB) is a critical component of traumatic brain injury (TBI) progression. However, further research into the mechanism of BBB disruption and its specific role in TBI pathophysiology is necessary. To help make progress in elucidating TBI affected BBB pathophysiology, we report herein relative gene expression of eleven TBI biomarkers and other factors of neuronal function in human brain microvascular cells (HBMVEC), one of the main cell types in the BBB. Our in-vitro blast TBI model employs a custom acoustic shock tube to deliver injuries of varying intensities to HBMVECs in culture. Each of the investigated genes exhibit a significant change in expression as a response to TBI, which is dependent on both the injury intensity and time following the injury. This data suggests that cell signaling of HBMVECs could be essential to understanding the interaction of the BBB and TBI pathophysiology, warranting future investigation.

JNK1 and JNK3 play a significant role in both neuronal apoptosis and necrosis. Evaluation based on in vitro approach using tert-butylhydroperoxide induced oxidative stress in neuro-2A cells and perturbation through 3-aminobenzamide.

In spinal cord injury (SCI), oxidative stress in the penumbra of the injury site is a characteristic feature. The predominance of necrosis over apoptosis in the ensuing delayed cell death results in progressive waves of necrosis affecting neighboring cells and thus exaggerates the severity of the lesion. Necrosis has been classified into subtypes based on the active molecular players and parthanatos is one among them, which is characterized by the over activation of PARP1 as the pre-mitochondrial event that triggers necrosis. Parthanatos being the necrosis mode reported in SCI, we intended to study the molecular players in the elusive pre-mitochondrial events of PARP1 over activation using an in vitro model. tert-Butylhydroperoxide (tBuOOH) was reported to induce oxidative stress in various cell types including Neuro-2A cells. Using a tailored protocol, a predominantly PARP1 mediated necrotic mode of cell death was obtained in Neuro-2A cells using tBuOOH. By perturbing the progress of necrosis using 3-amniobenzamide, a known PARP1 inhibitor, it was found that JNK1 and JNK3 but not JNK2 were involved in pre-mitochondrial stages of PARP1 mediated cell death. Given that JNK1 and JNK3 play a role in apoptosis also, they may serve as common targets to counter both apoptosis and necrosis. The in vitro model used in the present study may be useful in delineating molecular mechanisms in necrosis.

Effect of manganese and manganese plus noise on auditory function and cochlear structures.

The degenerative actions of Mn caused by persistent exposure to high atmospheric levels not only provokes irreversible damage to the CNS with symptoms comparable to that of Parkinson's disease but also may have deleterious consequences to other organs including the auditory system. The putative deleterious consequences of prolonged Mn overexposure on hearing, however, is confounded by the fact that chronically-exposed individuals often work in high noise environments where noise by itself is known to cause hearing loss. Thus, the question as to whether Mn alone is actually ototoxic and whether exposure to Mn when combined with noise increases the risk of hearing loss and cochlear pathology has never been examined. To examine whether noise effects Mn ototoxicity, we exposed rats to a moderate dose of Mn (10mg MnCl2/liter water) alone, a high level of noise (octave band noise, 8-16kHz, presented at 90dB SPL for 8h/d) alone or the combination of Mn plus noise and measured the changes in auditory function and the cochlear histopathologies. Results of these studies, based on various measures of hearing including histological examination of cochlear tissue suggest that noise alone produced significant hearing deficits whereas semi-chronic exposure to moderate levels of Mn in drinking water for 90days either in the presence or absence of noise had, at best, only a minor effect on hearing.

N-acetyl-cysteine prevents age-related hearing loss and the progressive loss of inner hair cells in γ-glutamyl transferase 1 deficient mice.

Genetic factors combined with oxidative stress are major determinants of age-related hearing loss (ARHL), one of the most prevalent disorders of the elderly. Dwarf grey mice, Ggt1dwg/dwg, are homozygous for a loss of function mutation of the g-glutamyl transferase 1 gene, which encodes an important antioxidant enzyme critical for the resynthesis of glutathione (GSH). Since GSH reduces oxidative damage, we hypothesized that Ggt1dwg/dwg mice would be susceptible to ARHL. Surprisingly, otoacoustic emissions and cochlear microphonic potentials, which reflect cochlear outer hair cell (OHC) function, were largely unaffected in mutant mice, whereas auditory brainstem responses and the compound action potential were grossly abnormal. These functional deficits were associated with an unusual and selective loss of inner hair cells (IHC), but retention of OHC and auditory nerve fibers. Remarkably, hearing deficits and IHC loss were completely prevented by N-acetyl-L-cysteine, which induces de novo synthesis of GSH; however, hearing deficits and IHC loss reappeared when treatment was discontinued. Ggt1dwg/dwg mice represent an important new model for investigating ARHL, therapeutic interventions, and understanding the perceptual and electrophysiological consequences of sensory deprivation caused by the loss of sensory input exclusively from IHC.

Neuroprotective role of naringenin on carbaryl induced neurotoxicity in mouse neuroblastoma cells.

OBJECTIVE: Neuroprotective effect of naringenin against carbaryl toxicity was studied in mouse neuroblastoma cell line. MATERIALS AND METHODS: Mouse neuroblastoma cells (Neuro 2A) obtained from National Center for Cell Sciences, Pune, India were either exposed to carbaryl or pre-treated with naringenin (a flavonoid prepared from grape fruit) before their exposure to carbaryl. Results were analyzed using MTT [3-4,5-Dimethylthiazol-2-yl)-2,5-diphenltetrazolium bromide] assay for cell viability, FACS (fluorescence assisted cell sorting) analysis for apoptotic and necrotic cell populations, DCFH-DA (2`,7`-dichlorofluorescin-diacetate) assay for Reactive Oxygen Species (ROS) visualization, JC-1 staining for determining mitochondrial membrane potential and real-time PCR for quantifying pro and anti-apoptotic gene expression. RESULTS: Exposure to naringenin resulted in better survival of Neuro 2A cells which were subsequently subjected to carbaryl toxicity. Treatment with naringenin was found to reduce the oxidative stress by decreasing the ROS and was found to maintain the integrity of mitochondrial membrane potential. It was also found to downregulate pro-apoptotic genes (BAX and Caspase-3) while upregulating anti-apototic gene (Bcl2). CONCLUSION: The results of this pilot study underline the potential of naringenin in treating carbaryl induced neurotoxicity and further studies are warranted to establish the effect of naringenin in vivo conditions.

Impact of occupational health hazards on serum markers of bone formation in spray painters of Chennai region in Tamil Nadu.

CONTEXT: The association between spray paint exposure and bone remodeling received little attention despite the high usage of spray paints in automobile industries, steel furniture workshops etc. AIM: The present study was aimed at investigating the level of serum markers of bone formation in spray painters. The spray painting subjects were selected from automobile body repair workshops in Chennai region of TamilNadu which constitutes 30% of India's automobile industry. SETTING AND DESIGN: All the study subjects, exposed to spray paint were working in a workshop without standard spraying room and did not wore any aerosol removing respirator. The controls were selected from random population irrespective of occupation. Data relevant to the socioeconomic features and personal history was collected using a questionnaire. The current study included 50 spray painters and 25 control subjects of same age group. MATERIALS AND METHODS: We examined the level of serum calcium, serum phosphorus, serum differentiation markers of bone such as alkaline phosphatase (bone specific) and serum osteocalcin in which these levels were found to be high in serum of spray painters. CONCLUSION: The current study concludes dysregulation in bone remodeling of spray painters exposed to chronic solvents and paint pigments.