Immunophyllin Ligands Show Differential Effects on Alcohol Self-Administration in C57BL Mice

Abstract

High abstinence rates characterize alcohol-dependent liver graft recipients. The immunosuppressants cyclosporine A (CsA) and tacrolimus (TRL) also inhibit calcineurin (CLN) in the brain. Previously, we found that CsA reduces alcohol consumption in C57BL/6J mice. The goals of the present study were: 1) to compare the ethanol preference effects of CsA against TRL, as well as sirolimus (SRL), an immunosuppressant without CLN inhibition and 2) to establish that reduction of alcohol consumption is not caused by caloric reinforcement from these ligands. C57BL/6J mice trained to imbibe ethanol consumed ethanol or sucrose in a modified limited-access drinking-in-the-dark paradigm; test groups received vehicle or doses of CsA (5-50 mg/kg), TRL (0.5-2.5 mg/kg), or SRL (1.0 -5.0 mg/kg) for 5 consecutive days, 30 min before each 2-h limited-access session. Brain CsA, TRL, and SRL concentrations were measured. CsA (p Ͻ 0.001) and TRL (p Ͻ 0.01) each decreased ethanol consumption, whereas SRL showed no significant effects at any dose. Effective doses included CsA at 10 mg/kg and above and TRL at 2.5 mg/kg. CsA (50 mg/kg) did not reduce sucrose consumption. Both CsA and TRL reached significant brain concentrations compared with very low values of SRL. These data suggest that CsA and TRL may reduce alcohol preference through central CLN inhibition rather than by immunosuppression.

Effects of Tacrolimus and Other Immune Targeting Compounds on Binge-Like Ethanol Drinking in High Drinking in the Dark Mice

“…Tacrolimus, a calcineurin inhibitor, has been shown to reduce limited-access ethanol intake in male C57BL/6J mice. 28 Here, we examined whether tacrolimus would reduce binge-like ethanol intake in male and female HDID-1 mice. Experimental procedures are shown in Figure 1a .…”

“…The presently used HDID-1 mice represent a unique, genetic risk model in which to screen the efficacy of promising neuroimmune and neuroinflammatory compounds. For the calcineurin inhibitor, tacrolimus, we were informed by the work of Beresford et al, 28 whereby 2.5 mg/kg of tacrolimus decreased 10% ethanol preference and intake in C75BL/6J male mice. Neasta et al 31 reported that systemic administration of the mTOR inhibitor, sirolimus (rapamycin), significantly reduced conditioned place preference to ethanol in DBA/2J male mice and reduced 20% ethanol intake in male C75BL/6J mice when given every other day, for 4 hours (beginning 2 hours into the dark cycle).…”

“…Doses and route of administration were chosen based on previously published levels and preliminary results on HDID-1 mice. 28 Ethanol fluid levels were read at 2 and 4 hours. Immediately after the 4-hour time point on Day 2, a 20 μl blood sample was taken from the peri-orbital sinus to determine BALs using gas chromatography.…”

“…Experimental procedures for the first week are shown in Figure 2a. Ethanol intake for Day 1 and across each 2-hour time period of Day 2 is shown in When administered once daily, sirolimus has been shown to reduce ethanol intake, 28 so we next examined whether the lack of effect of sirolimus was due to the timing of administration. Mice were re-randomized into new groups and assigned to receive either sirolimus (5 mg/kg) or vehicle, either 20 hours, 3 hours, or 30 minutes prior to ethanol access.…”

“…Tacrolimus is a macrolide calcineurin inhibitor and has been shown to reduce ethanol consumption in a C57BL/6J mice. 27 , 28 Tacrolimus was initially FDA approved as an immunosuppressant for organ transplantation in 1994 and is now a commonly used immunosuppressant. 29 Sirolimus (rapamycin) is another FDA approved (in 1999) immunosuppressant that targets the mTOR complex.…”