Comparison of ethanol and acetaldehyde toxicity in rat astrocytes in primary culture

Astrocyte DNA damage and response upon acute exposure to ethanol and corticosterone

Introduction: Astrocytes are the glial cells responsible for brain homeostasis, but if injured, they could damage neural cells even deadly. Genetic damage, DNA damage response (DDR), and its downstream cascades are dramatic events poorly studied in astrocytes. Hypothesis and methods: We propose that 1 h of 400 mmol/L ethanol and/or 1 μmol/L corticosterone exposure of cultured hippocampal astrocytes damages DNA, activating the DDR and eliciting functional changes. Immunolabeling against γH2AX (chromatin DNA damage sites), cyclin D1 (cell cycle control), nuclear (base excision repair, BER), and cytoplasmic (anti-inflammatory functions) APE1, ribosomal nucleolus proteins together with GFAP and S100β plus scanning electron microscopy studies of the astrocyte surface were carried out. Results: Data obtained indicate significant DNA damage, immediate cell cycle arrest, and BER activation. Changes in the cytoplasmic signals of cyclin D1 and APE1, nucleolus number, and membrane-attached vesicles strongly suggest a reactivity like astrocyte response without significant morphological changes. Discussion: Obtained results uncover astrocyte genome immediate vulnerability and DDR activation, plus a functional response that might in part, be signaled through extracellular vesicles, evidencing the complex influence that astrocytes may have on the CNS even upon short-term aggressions.

Genetic variation in alcohol dehydrogenase is associated with neurocognition in men with HIV and history of alcohol use disorder: preliminary findings

The co-occurrence of HIV and alcohol use disorder (AUD) amplifies risk for neural injury and neurocognitive deficits. However, the substantial neurocognitive heterogeneity across HIV+/AUD+ individuals suggests inter-individual differences in vulnerability to the neurotoxicity of comorbid HIV/AUD. Genetic variation in alcohol dehydrogenase (ADH), which metabolizes ethanol, may contribute to inter-individual neurocognitive variability. We evaluated associations between five ADH single-nucleotide polymorphisms (SNPs) and neurocognition in men stratified by HIV and lifetime AUD status. Neurobehavioral assessments were administered to 153 men. Three-way ANOVAs examined the interaction of HIV, AUD, and ADH SNPs on global and domain-specific demographically corrected T scores. Follow-up ANCOVAs adjusted for age, estimated verbal IQ, depression, and remote non-alcohol substance use disorders. HIV/AUD groups differed globally and for verbal fluency, working memory, executive function, and processing speed T scores specifically, with HIV+/AUD+ exhibiting the poorest performance. ADH4 (rs1126671) was associated with large effects on working memory (d = - 1.16, p = .001) and executive function (d = - 0.77, p = .028) selectively in HIV+/AUD+, which remained significant in ANCOVA models. ADH1A (rs3819197) moderated the deleterious effects of HIV+/AUD+ on processing speed such that HIV+/AUD+ related to slower information processing in A allele carriers but not GG homozygotes (ps < 0.03). Preliminary findings suggest genetic variation in the ADH pathway moderates the deleterious neurocognitive effects of comorbid HIV/AUD. Differential metabolism of heavy ethanol exposure may compromise neurocognition under conditions of neurobiological stress, such as in HIV infection. The functional effects on ethanol metabolism of ADH SNPs examined in this study remain poorly understood, warranting further examination of pharmacokinetic mechanisms mediating ADH gene-neurobehavior relationships in HIV.

Cytosolic non-vesicular dopamine accumulation as the predominant mechanism for developing non-DOPA responsive parkinsonism in late-stage Huntington disease

Disturbances in motor movement can have similar clinical presentations, albeit having different pathways and temporal onset. Hypokinetic movements present with rigidity, resting tremors, postural instability and bradykinesia, as seen in parkinsonism, while hyperkinetic movements typically present with chorea, ballismus, tic, athetosis and dystonia. Nonetheless, movement disorders are thought to be a continuum. Long-term therapy of parkinsonism with L-DOPA or dopamine (DA) agonists leads to late-onset dyskinesia - a hyperkinetic movement disorder, while patients with late-stage Huntington disease (HD) often develop non-DOPA responsive parkinsonism. In this paper, it is proposed that late-onset parkinsonism is driven by the overactivity of the nigrostriatal dopaminergic pathway. The excessive synthesis, storage, release, reuptake and degradation of dopamine in the presynaptic terminal and synaptic clefts lead to cellular stress and damage, resulting to progressive neuroapoptosis aggravated by pro-parkinsonism drugs used to treat hyperkinesia. Glutamate excitotoxicity may provide initial stress to neurons during early HD - but as the disease advances, lower glutamate levels are observed, making it less likely to cause the hypokinetic shift on its own. Over time, dopaminergic neurons are depleted and cholinergic influence to striatal GABA release is unopposed, leading to late-onset parkinsonism that is unresponsive to DOPA challenge, due to drastic DA neuron loss previously masked by the dominating choreic presentation. This paper thus provides a mechanism of action to a common clinical sequela and complication of long-term choreic diseases, whose pathophysiologic mechanism is presently lacking.

Estrogen Receptors α and β Play Major Roles in Ethanol-Evoked Myocardial Oxidative Stress and Dysfunction in Conscious Ovariectomized Rats

BACKGROUND

We documented the dependence of ethanol (EtOH)-evoked myocardial dysfunction on estrogen (E₂ ), and our recent estrogen receptor (ER) blockade study, in proestrus rats, implicated ERα signaling in this phenomenon. However, a limitation of selective pharmacological loss-of-function approach is the potential contribution of the other 2 ERs to the observed effects because crosstalk exists between the 3 ERs. Here, we adopted a "regain"-of-function approach (using selective ER subtype agonists) to identify the ER subtype(s) required for unraveling the E₂ -dependent myocardial oxidative stress/dysfunction caused by EtOH in conscious ovariectomized (OVX) rats.

METHODS

OVX rats received a selective ERα (PPT), ERβ (DPN), or GPER (G1) agonist (10 μg/kg; i.v.) or vehicle 30 minutes before EtOH (1.0 g/kg; infused i.v. over 30 minutes) or saline, and the hemodynamic recording continued for additional 60 minutes. Thereafter, left ventricular tissue was collected for conducting ex vivo molecular/biochemical studies.

RESULTS

EtOH had no hemodynamic effects in OVX rats, but reduced the left ventricular contractility index, dP/dt_max , and MAP after acute ERα (PPT) or ERβ (DPN) activation. These responses were associated with increases in the phosphorylation of ERK1/2 and eNOS, and in reactive oxygen species (ROS) and malondialdehyde (MDA) levels in the myocardium. GPER activation (G1) only unraveled a modest EtOH-evoked hypotension and elevation in myocardial ROS. PPT enhanced catalase, DPN reduced ALDH2, while G1 had no effect on the activity of either enzyme, and none of the agonists influenced alcohol dehydrogenase or CYP2E1 activities in the myocardium. Blood EtOH concentration (96.0 mg/dl) was significantly reduced following ERα (59.8 mg/dl) or ERβ (62.9 mg/dl), but not GPER (100.3 mg/dl), activation in EtOH-treated OVX rats.

CONCLUSIONS

ERα and ERβ play major roles in the E₂ -dependent myocardial dysfunction caused by EtOH by promoting combined accumulation of cardiotoxic (ROS and MDA) and cardiodepressant (NOS-derived NO) molecules in female myocardium.

Cytosolic phospholipase A2 regulates alcohol-mediated astrocyte inflammatory responses in HIV-associated neurocognitive disorders

Alcohol (EtOH) abuse and HIV-1 infection remain leading public health problems not only in the United States but also across the world. Alcohol abusers have a significantly greater risk of HIV-1 infection than non-drinkers globally. In the United States, prevalence of EtOH abuse is over two-fold higher in HIV-1-positive individuals than that of the general population. Although alcohol abusers show neurodegeneration, exacerbated neuroinflammation and oxidative damage, the mechanism(s) by which EtOH regulates astrocyte inflammatory responses in HIV-associated neurocognitive disorders is unknown. Thus, we explored signaling pathway(s) involved in EtOH-mediated activation of human astrocytes with HIV-1 and subsequent alterations in their inflammatory functions. Alcohol exposure altered the morphology of astrocytes, proinflammatory responses and induced cytotoxicity in a dose-dependent manner. Time-dependent changes were also evaluated. EtOH and HIV-1 cotreatment decreased cell viability and proliferation, while increasing apoptosis and mitochondrial depolarization. EtOH and HIV-1 together increased the levels of proinflammatory molecules, interleukin-1β, tumor necrosis factor-α, CXCL8, tissue inhibitor of metalloproteinases-1 and more importantly, arachidonic acid, a known downstream target of cytosolic phospholipase A₂ (cPLA₂). Consistent with this observation, phospho-cPLA₂ levels were augmented in HIV-1 and EtOH cotreatment as compared with HIV-1 or EtOH alone. Cyclooxygenase 2 was upregulated as measured by real-time PCR and western blot, whereas cotreatment of HIV-1 and EtOH decreased cytochrome P450-2E1 levels as compared with EtOH alone. Furthermore, we confirmed that blocking cPLA₂ with arachidonyl tri floro methyl ketone, a cPLA₂-specific inhibitor, effectively prevented cPLA₂ phosphorylation and downstream outcomes. Thus, the present findings suggest that cPLA₂ has a critical role in alcohol and HIV-induced astrocyte inflammation. In the future, cPLA₂ inhibitors may present novel therapeutic tools to treat alcohol abuse and HIV-associated neurocognitive disorder comorbidity.

Ethanol and acetaldehyde disturb TNF-alpha and IL-6 production in cultured astrocytes

Ethanol disturbs astroglial growth and differentiation and causes functional alterations. Furthermore, many signalling molecules produced by astrocytes contribute to these processes. The aim of the present study was to investigate the influence of ethanol and its primary metabolite, acetaldehyde, on TNF-alpha and IL-6 production in a rat cortical astrocyte primary culture. We are the first to report that both ethanol and acetaldehyde can modulate TNF-alpha and IL-6 secretion from cultured astrocytes. Long-term exposure (7 days) to ethanol and acetaldehyde was more toxic than an acute (24 hours) exposure. However, both compounds showed a biphasic, hormestic effect on the IL-6 secretion after the acute as well as the long-term exposure, and the maximum stimulation was reached for 50-mM ethanol and 1-mM acetaldehyde after 7-day exposure. In contrast, both compounds reduced the TNF-alpha secretion, where the effect was concentration-dependent. The catalase inhibitor 2-amino-1,2,4 triazole significantly reduced the ethanol toxicity in the cultured astrocytes after the acute as well as the long-term exposure. In conclusion, both ethanol and acetaldehyde affect the production of IL-6 and TNF-alpha in cultured astrocytes. The effect depends on the concentration of the compounds and the duration of the exposure. Acetaldehyde is a more potent toxin than ethanol, and ethanol's toxicity in the brain is at least partially due to its primary metabolite, acetaldehyde.