Adult rats episodically intoxicated with alcohol (ethanol)-e.g., 8-12 g/kg/d in fractional doses for 4 days, or simply one daily dose (4-6 g/kg) for 6-10 days-incur brain damage, as revealed by a specific neurodegeneration stain, in selected limbic cortical regions and the olfactory bulbs. Also, organotypic rat brain slice cultures treated episodically with alcohol (100-200 mM) for 6 days show evidence of induced cytotoxic damage. The underlying mechanism(s) is apparently not excitotoxic or seizure-related, because (a) the brain damage in vivo was not significantly diminished by glutamate receptor antagonists, a Ca++ channel blocker, or by nitric oxide synthase inhibitors; and (b) hippocampal CA regions, which are highly vulnerable to seizure damage, were largely unaffected. However, the brains of rats treated once daily with alcohol for a week were edemic and showed Na+ and K+ accumulation. Suspecting a role for edema, we examined the effect of furosemide, a potent diuretic and inhibitor of the C1- transporter that nonsynaptically blocks brain cell swelling in animal epilepsy models. Indeed, furosemide co-treatment significantly reduced alcohol-induced cortical neurodegeneration by 75-85 percent as it prevented the brain edema and electrolyte accumulation. Furthermore, furosemide completely blocked cytotoxicity in organotypic rat brain slice cultures exposed episodically to alcohol. This appears to be the first demonstration of significant neuroprotection during binge alcohol exposure. Hypothesizing brain edema as an key early step in the neurodegeneration, we propose in this R21 application to explore the generality of neuroprotection by studying three other diuretics, acetazolamide, chlorthalidone and torsemide along with a nondiuretic furosemide analog (L-644, 711) in our in vivo/in vitro approach.
In Aim 1, neuroprotection from brain edema and degeneration for four agents will be examined in male rats intoxicated once daily with alcohol for an 8 day period. Concurrently, plasma vasopressin, and plasma and urine osmolality will be assessed to facilitate interpretation of results. Also, brain cell swelling and number will be measured stereologically in the alcohol-treated rats.
In Aim II, the four agents will be examined with mature organotypic rat cortical/hippocampal slice cultures, in which both cytotoxicity (LDH release) and brain cell swelling by biochemical (taurine release) and morphometric (stereology) measurements will be determined. We anticipate that reductions in brain edema and neurodegeneration in vivo will tend to be reproduced in vitro, accompanied by prevention of cell swelling. The results can potentially provide new therapeutic approaches to neuroprotection in alcoholism, and can lay the groundwork for future detailed studies on possibly novel mechanisms underlying brain damage due to episodic alcohol exposure.
| Moon, Kwan-Hoon; Tajuddin, Nuzhath; Brown 3rd, James et al. (2014) Phospholipase A2, oxidative stress, and neurodegeneration in binge ethanol-treated organotypic slice cultures of developing rat brain. Alcohol Clin Exp Res 38:161-9 |
| Collins, Michael A; Neafsey, Edward J (2012) Ethanol and adult CNS neurodamage: oxidative stress, but possibly not excitotoxicity. Front Biosci (Elite Ed) 4:1358-67 |
| Collins, Michael A; Neafsey, Edward J (2012) Neuroinflammatory pathways in binge alcohol-induced neuronal degeneration: oxidative stress cascade involving aquaporin, brain edema, and phospholipase A2 activation. Neurotox Res 21:70-8 |
| Sripathirathan, Kumar; Brown 3rd, James; Neafsey, Edward J et al. (2009) Linking binge alcohol-induced neurodamage to brain edema and potential aquaporin-4 upregulation: evidence in rat organotypic brain slice cultures and in vivo. J Neurotrauma 26:261-73 |
