Intoxication‐ and Withdrawal‐Dependent Expression of Central and Peripheral Cytokines Following Initial Ethanol Exposure

Abstract

Background Evidence has emerged demonstrating that ethanol influences cytokine expression within the CNS, although most studies have examined long-term exposure. Thus, the cytokine response to an acute ethanol challenge was investigated, in order to characterize profiles of cytokine changes following acute exposure. Methods Rats pups were injected intraperitoneally (i.p.) with 2-g/kg ethanol and IL-1 mRNA and protein assessed 0, 60, 120, 180, and 240 min post-injection (Exp. 1). In Exps. 2-5, the expression of several cytokines was examined in adult male rats during acute intoxication (3 hr after 4-g/kg ethanol), as well as withdrawal (18 hr post-injection), after i.p. and intragastric (i.g.) ethanol administration. Results Early in ontogeny, acute ethanol significantly decreased brain IL-1 mRNA and protein. Subsequently, when adult rats were examined, significant and temporally dynamic alterations in central and peripheral cytokines were observed following acute i.p. ethanol exposure (4-g/kg). Although cytokine- and region-dependent, central IL-6 expression was generally increased and TNFα decreased during intoxication, whereas IL-1 expression exhibited increases during withdrawal. In the periphery, acute i.p. ethanol elevated expression of all cytokines, with the response growing in magnitude as the time post-injection increased. Following acute i.g. ethanol (4-g/kg), intoxication-related increases in IL-6 expression were again observed in the PVN, although to a lesser extent. Long-term, voluntary, intermittent ethanol consumption resulted in tolerance to the effects of an i.g. ethanol challenge (4-g/kg) on PVN IL-6 expression, whereas these same elevations in IL-6 expression were still seen in the amygdala in rats with a history of moderate ethanol intake. Treatment with minocycline did not significantly attenuate i.p. or i.g. ethanol-induced changes in central cytokine expression. Conclusions Together, these studies provide a foundation for understanding fluctuations in central and peripheral cytokines following acute ethanol as potential contributors to the constellation of neural and behavioral alterations observed during ethanol intoxication and withdrawal.

Male adolescent rats display blunted cytokine responses in the CNS after acute ethanol or lipopolysaccharide exposure

“…ethanol as potential drivers of endotoxin transit into blood, and whether such responses might differentially impact the action of ethanol on brain cytokines following these two commonly used modes of ethanol administration. Our a priori hypothesis was that ethanol exposure (regardless of route or age) would evoke central cytokine changes consistent with our previous findings (i.e., increased IL-6, decreased IL-1 and TNF; see [39]), and that these changes would occur independent of plasma endotoxin alterations. Together, the side-by-side comparison of LPS and ethanol challenge with multiple, within-subject, physiological measures (e.g., plasma measures of corticosterone, endotoxin, and blood ethanol content; plus cytokine measures in several key CNS structures) was expected to fully elucidate the nature of age-related differences in neuroimmune consequences of ethanol, and to inform future directions for identifying the mechanisms underlying any developmental differences observed.…”

“…A single peak expressed as the negative first derivative of the change in fluorescence as a function of temperature indicated primer specificity to the target gene. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was used as a reference gene in these experiments, as studies from our laboratory have revealed more stable gene expression across ethanol treatment conditions with this gene [e.g., 39]. Primer sequences and a brief description of gene function can be found in Table 1.…”

“…Previous studies from our laboratory have identified highly reproducible changes in central cytokine expression following an acute ethanol challenge in adult rats [Gano et al, in prep; 39]. While these ethanol-related alterations in brain cytokine expression are dependent upon brain area of interest, cytokine of interest, and the time at which cytokine expression is examined after ethanol administration, a consistent increase in IL-6 gene expression has been observed in the hippocampus, PVN, amygdala, and cerebellum in adult male rats during the intoxication phase after a binge-like dose (4 g/kg) of ethanol.…”

“…In adults, we have recently shown that marked changes in cytokine gene expression are apparent in the adult brain during the first ethanol exposure, with these changes dose-, time-, and regionally-dependent in nature [39]. More specifically, an acute 4-g/kg ethanol challenge consistently and significantly increased expression of IL-6 during intoxication in the paraventricular nucleus of the hypothalamus (PVN), hippocampus, cerebellum, and amygdala, whereas decreased expression of IL-1 and TNFα was generally observed in these same structures during intoxication [39]. In contrast, withdrawal from an acute ethanol challenge was not shown to result in marked alterations in cytokine expression, with IL-1 expression sometimes elevated relative to non-ethanol-exposed controls.…”

Endogenous opioids as substrates for ethanol intake in the neonatal rat: The impact of prenatal ethanol exposure on the opioid family in the early postnatal period

“…Studies that have made use of radioimmunoassay have successfully found increases in met-enkephalin, the endogenous ligand for the DOR, within the nAC and hypo following a similar prenatal manipulation [34]. While future studies will be necessary to clarify the reasons for the dissociation between mRNA and protein observed here, such effects are common (e.g., [48] and [49], but see [50]) and underscore the importance of examining both mRNA and protein as a function of experimental treatment. Regardless, the present data provide important information regarding functional plasticity of the opioid system across early ontogeny and highlight the vulnerability of this system to prenatal programming effects of PAE.…”