Role of Endoplasmic Reticulum Stress in the Amygdaloid Kindling Model of Rats

Plasma alpha B crystallin as potential biomarker for predicting pre-operative seizures in glioma

PURPOSE

Glioma-associated epilepsy affects a significant proportion of glioma patients, contributing to disease progression and diminished survival rates. However, the lack of a reliable preoperative seizure predictor hampers effective surgical planning. This study investigates the potential of Alpha B crystallin protein (CRYAB) plasma levels as a predictive biomarker for epilepsy seizures in glioma patients.

METHODS

Plasma samples were obtained from 75 participants, including 21 glioma patients with pre-operative epilepsy, 14 glioma patients without pre-operative epilepsy, and 21 age- and sex-matched control subjects. Additionally, 11 idiopathic epilepsy patients and 8 intractable epilepsy patients served as positive disease control groups. The study utilized ELISA to accurately quantify the circulating levels of CRYAB in the plasma samples of all participants.

RESULTS

The analysis revealed a significant reduction in plasma CRYAB levels in glioma patients with pre-operative epilepsy and idiopathic epilepsy. The receiver operating characteristic (ROC) curve analysis displayed an impressive performance, indicating an AUC of 0.863 (95% CI, 0.810-0.916) across the entire patient cohort. Furthermore, plasma CRYAB levels exhibited a robust diagnostic capability, with an AUC of 0.9135, a sensitivity of 100.0%, and a specificity of 73.68%, effectively distinguishing glioma patients with preoperative epilepsy from those without epilepsy. The Decision Curve Analysis (DCA) underscored the clinical relevance of plasma CRYAB levels in predicting pre-operative epilepsy in glioma.

CONCLUSION

The findings imply that the reduced levels of CRYAB may assist in prediction of seizure occurrence in glioma patients, although future large-scale prospective studies are warranted.

Profiling the Expression of Endoplasmic Reticulum Stress Associated Heat Shock Proteins in Animal Epilepsy Models

Unfolded protein response is a signaling cascade triggered by misfolded proteins in the endoplasmic reticulum. Heat shock protein H4 (HSPH4) and A5 (HSPA5) are two chaperoning proteins present within the organelle, which target misfolded peptides during prolonged stress conditions. Epileptogenic insults and epileptic seizures are a notable source of stress on cells. To investigate whether they influence expression of these chaperones, we performed immunohistochemical stainings in brains from rats that experienced a status epilepticus (SE) as a trigger of epileptogenesis and from canine epilepsy patients. Quantification of HSPA5 and HSPH4 revealed alterations in hippocampus and parahippocampal cortex. In rats, SE induced up-regulation of HSPA5 in the piriform cortex and down-regulation of HSPA5 and HSPH4 in the hippocampus. Regionally restricted increases in expression of the two proteins has been observed in the chronic phase with spontaneous recurrent seizures. Confocal microscopy revealed a predominant expression of both proteins in neurons, no expression in microglia and circumscribed expression in astroglia. In canine patients, only up-regulation of HSPH4 expression was observed in Cornu Ammonis 1 region in animals diagnosed with structural epilepsy. This characterization of HSPA5 and HSPH4 expression provided extensive information regarding spatial and temporal alterations of the two proteins during SE-induced epileptogenesis and following epilepsy manifestations. Up-regulation of both proteins implies stress exerted on ER during these disease phases. Taken together suggest a differential impact of epileptogenesis on HSPA5 and HSPH4 expression and indicate them as a possible target for pharmacological modulation of unfolded protein response.

Exercise influence on the microbiome-gut-brain axis

The microbiome in the gut is a diverse environment, housing the majority of our bacterial microbes. This microecosystem has a symbiotic relationship with the surrounding multicellular organism, and a balance and diversity of specific phyla of bacteria support general health. When gut bacteria diversity diminishes, there are systemic consequences, such as gastrointestinal and psychological distress. This pathway of communication is known as the microbiome-gut-brain axis. Interventions such as probiotic supplementation that influence microbiome also improve both gut and brain disorders. Recent evidence suggests that aerobic exercise improves the diversity and abundance of genera from the Firmcutes phylum, which may be the link between the positive effects of exercise on the gut and brain. The purpose of this review is to explain the complex communication pathway of the microbiome-gut-brain axis and further examine the role of exercise on influencing this communication highway.

Neuronal Nitric Oxide Synthase Contributes to PTZ Kindling Epilepsy-Induced Hippocampal Endoplasmic Reticulum Stress and Oxidative Damage

Epilepsy is one of the most common chronic neurological disorders which provoke progressive neuronal degeneration. Endoplasmic reticulum (ER) stress has recently been recognized as pivotal etiological factors contributing to epilepsy-induced neuronal damage. However, the specific contribution of epilepsy made to ER stress remains largely elusive. Here we use pentylenetetrazole (PTZ) kindling, a chronic epilepsy model, to identify neuronal nitric oxide synthase (nNOS) as a signaling molecule triggering PTZ kindling epilepsy-induced ER stress and oxidative damage. By genetic deletion of nNOS gene, we further demonstrated that nNOS acts through peroxynitrite, an important member of reactive nitrogen species, to trigger hippocampal ER stress and oxidative damage in the PTZ-kindled mice. Our findings thus define a specific mechanism for chronic epilepsy-induced ER stress and oxidative damage, and identify a potential therapeutic target for neuroprotection in chronic epilepsy patients.

Protective effects of N-acetylcysteine against monosodium glutamate-induced astrocytic cell death

Monosodium glutamate (MSG) is a flavor enhancer, largely used in the food industry and it was reported to have excitotoxic effects. Higher amounts of MSG consumption have been related with increased risk of many diseases, including Chinese restaurant syndrome and metabolic syndromes in human. This study investigated the protective effects of N-acetylcysteine (NAC) on MSG-induced cytotoxicity in C6 astrocytic cells. MSG (20 mM)-induced reactive oxygen species (ROS) generation and apoptotic cell death were significantly attenuated by NAC (500 μM) pretreatment. NAC effectively inhibited the MSG-induced mitochondrial membrane potential (MMP) loss and intracellular reduced glutathione (GSH) depletion. In addition, NAC significantly attenuated MSG-induced endoplasmic reticulum (ER) stress markers, such as XBP1 splicing and CHOP, PERK, and GRP78 up-regulation. Furthermore, NAC prevented the changes of MSG-induced Bcl-2 expression level. These results suggest that NAC can protect C6 astrocytic cells against MSG-induced oxidative stress, mitochondrial dysfunction, and ER stress.

CHOP regulates the p53-MDM2 axis and is required for neuronal survival after seizures

Hippocampal sclerosis is a frequent pathological finding in patients with temporal lobe epilepsy and can be caused by prolonged single or repeated brief seizures. Both DNA damage and endoplasmic reticulum stress have been implicated as underlying molecular mechanisms in seizure-induced brain injury. The CCAAT/enhancer-binding protein homologous protein (CHOP) is a transcriptional regulator induced downstream of DNA damage and endoplasmic reticulum stress, which can promote or inhibit apoptosis according to context. Recent work has proposed inhibition of CHOP as a suitable neuroprotective strategy. Here, we show that transcript and protein levels of CHOP increase in surviving subfields of the hippocampus after prolonged seizures (status epilepticus) in mouse models. CHOP was also elevated in the hippocampus from epileptic mice and patients with pharmacoresistant epilepsy. The hippocampus of CHOP-deficient mice was much more vulnerable to damage in mouse models of status epilepticus. Moreover, compared with wild-type animals, CHOP-deficient mice subject to status epilepticus developed more spontaneous seizures, displayed protracted hippocampal neurodegeneration and a deficit in a hippocampus-dependent object-place recognition task. The absence of CHOP was associated with a supra-maximal induction of p53 after status epilepticus, and inhibition of p53 abolished the cell death-promoting consequences of CHOP deficiency. The protective effect of CHOP could be partly explained by activating transcription of murine double minute 2 that targets p53 for degradation. These data demonstrate that CHOP is required for neuronal survival after seizures and caution against inhibition of CHOP as a neuroprotective strategy where excitotoxicity is an underlying pathomechanism.