Caspase-3 Activity in the Rat Amygdala Measured by Spectrofluorometry After Myocardial Infarction

Targeting DNA methylation can reduce cardiac injury associated with ischemia reperfusion: One step closer to clinical translation with blood-borne assessment

Ischemia reperfusion (I/R) injury is one of the main clinical challenges for cardiac surgeons. No effective strategies or therapy targeting the molecular and cellular mechanisms to reduce I/R exists to date, despite altered gene expression and cellular metabolism/physiology. We aimed to identify whether DNA methylation, an unexplored target, can be a potential site to curb I/R-associated cell death by using the left anterior descending artery occlusion model in male Wistar rats. I/R rat heart exhibited global DNA hypermethylation with a corresponding decline in the mitochondrial genes (PGC-1α, TFAM, POLG, ND1, ND3, ND4, Cyt B, COX1, and COX2), antioxidant genes (SOD2, catalase, and Gpx2) and elevation in apoptotic genes (Casp3, Casp7, and Casp9) expression with corresponding changes in their activity, resulting in injury. Targeting global DNA methylation in I/R hearts by using its inhibitor significantly reduced the I/R-associated infarct size by 45% and improved dysferlin levels via modulating the genes involved in cell death apoptotic pathway (Casp3, Casp7, and PARP), inflammation (IL-1β, TLR4, ICAM1, and MyD88), oxidative stress (SOD1, catalase, Gpx2, and NFkB) and mitochondrial function and its regulation (MT-ND1, ND3, COX1, ATP6, PGC1α, and TFAM) in the cardiac tissue. The corresponding improvement in the genes' function was reflected in the respective hearts via the reduction in apoptotic TUNEL positive cells and ROS levels, thereby improving myocardial architecture (H&E staining), antioxidant enzymes (SOD, catalase activity) and mitochondrial electron transport chain activities and ATP levels. The analysis of blood from the I/R animals in the presence and absence of methylation inhibition exhibited a similar pattern of changes as that observed in the cardiac tissue with respect to global DNA methylation level and its enzymes (DNMT and TET) gene expression, where the blood cardiac injury markers enzymes like LDH and CK-MB were elevated along with declined tissue levels. Based on these observations, we concluded that targeting DNA methylation to reduce the level of DNA hypermethylation can be a promising approach in ameliorating I/R injury. Additionally, the blood-borne changes reflected I/R-associated myocardial tissue alteration, making it suitable to predict I/R-linked pathology.

Differences in Evolution of Epileptic Seizures and Topographical Distribution of Tissue Damage in Selected Limbic Structures Between Male and Female Rats Submitted to the Pilocarpine Model

Epidemiological evidence shows that clinical features and comorbidities in temporal lobe epilepsy (TLE) may have different manifestations depending on the sex of patients. However, little is known about how sex-related mechanisms can interfere with the processes underlying the epileptic phenomenon. The findings of this study show that male rats with epilepsy in the pilocarpine model have longer-lasting and more severe epileptic seizures, while female rats have a higher frequency of epileptic seizures and a greater number of seizure clusters. Significant sex-linked pathological changes were also observed: epileptic brains of male and female rats showed differences in mass reduction of 41.8% in the amygdala and 18.2% in the olfactory bulb, while loss of neuronal cells was present in the hippocampus (12.3%), amygdala (18.1%), and olfactory bulb (7.5%). Another important sex-related finding was the changes in non-neuronal cells with increments for the hippocampus (36.1%), amygdala (14.7%), and olfactory bulb (37%). Taken together, our study suggests that these neuropathological changes may underlie the differences in the clinical features of epileptic seizures observed in male and female rats.

Cerebral derailment after myocardial infarct: mechanisms and effects of the signaling from the ischemic heart to brain

Myocardial infarction (MI) is the leading cause of death among ischemic heart diseases and is associated with several long-term cardiovascular complications, such as angina, re-infarction, arrhythmias, and heart failure. However, MI is frequently accompanied by non-cardiovascular multiple comorbidities, including brain disorders such as stroke, anxiety, depression, and cognitive impairment. Accumulating experimental and clinical evidence suggests a causal relationship between MI and stroke, but the precise underlying mechanisms have not yet been elucidated. Indeed, the risk of stroke remains a current challenge in patients with MI, in spite of the improvement of medical treatment among this patient population has reduced the risk of stroke. In this review, the effects of the signaling from the ischemic heart to the brain, such as neuroinflammation, neuronal apoptosis, and neurogenesis, and the possible actors mediating these effects, such as systemic inflammation, immunoresponse, extracellular vesicles, and microRNAs, are discussed.

Downregulation of GRK6 in arcuate nucleus promotes chronic visceral hypersensitivity via NF-κB upregulation in adult rats with neonatal maternal deprivation

AIMS

The arcuate nucleus is a vital brain region for coursing of pain command. G protein-coupled kinase 6 (GRK6) accommodates signaling through G protein-coupled receptors. Studies have demonstrated that GRK6 is involved in inflammatory pain and neuropathic pain. The present study was designed to explore the role and the underlying mechanism of GRK6 in arcuate nucleus of chronic visceral pain.

METHODS

Chronic visceral pain of rats was induced by neonatal maternal deprivation and evaluated by monitoring the threshold of colorectal distension. Western blotting, immunofluorescence, real-time quantitative polymerase chain reaction techniques, and Nissl staining were employed to determine the expression and mutual effect of GRK6 with nuclear factor κB (NF-κB).

RESULTS

Expression of GRK6 in arcuate nucleus was significantly reduced in neonatal maternal deprivation rats when compared with control rats. GRK6 was mainly expressed in arcuate nucleus neurons, but not in astrocytes, and a little in microglial cells. Neonatal maternal deprivation reduced the percentage of GRK6-positive neurons of arcuate nucleus. Overexpression of GRK6 by Lentiviral injection into arcuate nucleus reversed chronic visceral pain in neonatal maternal deprivation rats. Furthermore, the expression of NF-κB in arcuate nucleus was markedly upregulated in neonatal maternal deprivation rats. NF-κB selective inhibitor pyrrolidine dithiocarbamate suppressed chronic visceral pain in neonatal maternal deprivation rats. GRK6 and NF-κB were expressed in the arcuate nucleus neurons. Importantly, overexpression of GRK6 reversed NF-κB expression at the protein level. In contrast, injection of pyrrolidine dithiocarbamate once daily for seven consecutive days did not alter GRK6 expression in arcuate nucleus of neonatal maternal deprivation rats.

CONCLUSIONS

Present data suggest that GRK6 might be a pivotal molecule participated in the central mechanisms of chronic visceral pain, which might be mediated by inhibiting NF-κB signal pathway. Overexpression of GRK6 possibly represents a potential strategy for therapy of chronic visceral pain.

Leveraging the Comparative Toxicogenomics Database to Fill in Knowledge Gaps for Environmental Health: A Test Case for Air Pollution-induced Cardiovascular Disease

Environmental health studies relate how exposures (eg, chemicals) affect human health and disease; however, in most cases, the molecular and biological mechanisms connecting an exposure with a disease remain unknown. To help fill in these knowledge gaps, we sought to leverage content from the public Comparative Toxicogenomics Database (CTD) to identify potential intermediary steps. In a proof-of-concept study, we systematically compute the genes, molecular mechanisms, and biological events for the environmental health association linking air pollution toxicants with 2 cardiovascular diseases (myocardial infarction and hypertension) as a test case. Our approach integrates 5 types of curated interactions in CTD to build sets of "CGPD-tetramers," computationally constructed information blocks relating a Chemical- Gene interaction with a Phenotype and Disease. This bioinformatics strategy generates 653 CGPD-tetramers for air pollution-associated myocardial infarction (involving 5 pollutants, 58 genes, and 117 phenotypes) and 701 CGPD-tetramers for air pollution-associated hypertension (involving 3 pollutants, 96 genes, and 142 phenotypes). Collectively, we identify 19 genes and 96 phenotypes shared between these 2 air pollutant-induced outcomes, and suggest important roles for oxidative stress, inflammation, immune responses, cell death, and circulatory system processes. Moreover, CGPD-tetramers can be assembled into extensive chemical-induced disease pathways involving multiple gene products and sequential biological events, and many of these computed intermediary steps are validated in the literature. Our method does not require a priori knowledge of the toxicant, interacting gene, or biological system, and can be used to analyze any environmental chemical-induced disease curated within the public CTD framework. This bioinformatics strategy links and interrelates chemicals, genes, phenotypes, and diseases to fill in knowledge gaps for environmental health studies, as demonstrated for air pollution-associated cardiovascular disease, but can be adapted by researchers for any environmentally influenced disease-of-interest.

Assessment of arsenic-induced modifications in the DNA methylation of insulin-related genes in rat pancreatic islets

Extended exposure to inorganic arsenic through contaminated drinking water has been linked with increased incidence of diabetes mellitus. The most common exposure occurs through the consumption of contaminated drinking water mainly through geogenic sources of inorganic arsenic. Epigenetic modifications are important mechanisms through which environmental pollutants could exert their toxic effects. Bisulfite sequencing polymerase chain reaction method followed by Sanger sequencing was performed for DNA methylation analysis. Our results showed that sodium arsenite treatment significantly reduced insulin secretion in pancreatic islets. It was revealed that the methylation of glucose transporter 2 (Glut2) gene was changed at two cytosine-phosphate-guanine (CpG) sites (-1743, -1734) in the promoter region of the sodium arsenite-treated group comparing to the control. No changes were observed in the methylation status of peroxisome proliferator-activated receptor-gamma (PPARγ), pancreatic and duodenal homeobox 1 (Pdx1) and insulin 2 (Ins2) CpG sites in the targeted regions. Measuring the gene expression level showed increase in Glut2 expression, while the expression of insulin (INS) and Pdx1 were significantly affected by sodium arsenite treatment. This study revealed that exposure to sodium arsenite changed the DNA methylation pattern of Glut2, a key transporter of glucose entry into the pancreatic beta cells (β-cells). Our data suggested possible epigenetic-mediated toxicity mechanism for arsenite-induced β-cells dysfunction. Further studies are needed to dissect the precise epigenetic modulatory activity of sodium arsenite that affect the biogenesis of insulin.

Eventual analysis of global cerebral ischemia-reperfusion injury in rat brain: a paradigm of a shift in stress and its influence on cognitive functions

Cognitive issues in stroke arise as a result of reperfusion of a clogged artery, which is reported to exacerbate the injury in the brain leading to oxidative stress. Through the present work, we try to understand the regional variations across brain regions mainly cortex and striatum associated with the progression of ischemia-reperfusion injury (IRI). In a rat model of IRI, the influence of varying ischemia and reperfusion times on the biochemical phases across the brain regions were monitored. IRI resulted in the blood-brain barrier disruption and developed mild areas of risk. The brain's tolerance towards IRI indicated a progressive trend in the injury and apoptosis from ischemia to reperfusion that was supported by the activities of plasma lactate dehydrogenase and tissue caspase-3. Cognitive impairment in these rats was an implication of cellular oxidative stress (higher lipid peroxidation and lower antioxidant enzyme activity) that persisted by 24-h reperfusion. The oxidative stress was prominent in the cortex than the striatum and was supported by the lower ATP level. Upregulated Mn-SOD expression leading to a preserved mitochondria in the striatum could be attributed to the regional protection. Overall, a progression of IRI was observed from striatum to cortex leading to 5-day cognitive decline.

Temporal development of behavioral impairments in rats following locus coeruleus lesion induced by 6-hydroxydopamine: Involvement of β3-adrenergic receptors

Noradrenergic degeneration in the locus coeruleus (LC) seems a convergent neuropathological marker of different neurodegenerative diseases. Herein, we investigated the temporal development of apoptotic signaling activation in the LC, noradrenergic dysfunction and behavioral impairments in rats following the noradrenergic lesion of the LC. For this purpose, the dopamine reuptake inhibitor nomifensine was administered 1 h before the stereotaxic bilateral injections of 6-hydroxydopamine (6-OHDA; 5, 10 or 20 μg/hem) into the LC. The behavioral and neurochemical analyses were performed at 7, 21 and 42 days after 6-OHDA injections. All doses of 6-OHDA induced neuronal death in LC, but only the highest dose (20 μg/hem) disrupted the motor function. 6-OHDA (5 μg/hem) injection induced short-term memory deficits in all periods, olfactory discrimination and long-term memory impairments at 7 days, and depressive-like behaviors at 21 and 42 days after injection. Moreover, 6-OHDA infusion increased Bax/Bcl2 ratio and caspase 3 levels, and decreased the dopamine β-hydroxylase immunocontent in the LC. Noradrenergic neurotransmission dysfunction was observed in the LC, olfactory bulb, prefrontal cortex, hippocampus and striatum. The intranasal (i.n.) noradrenaline (NA) infusion restored the impairments in the olfactory discrimination, short-term memory and depressive-like behavior of 6-OHDA-lesioned rats. In addition, these effects were blocked by the prior i.n. infusion of the β₃-adrenergic receptor antagonist SR59230A. These findings indicate that the 6-OHDA injection into the LC induced the apoptosis signaling activation, noradrenergic neurotransmission dysfunction and behavioral impairments that were restored via β₃-adrenergic receptors activation mediated by the i.n. NA administration.