There is still no widely effective pharmacotherapy for alcohol addiction available in the clinic. FK506-binding protein 51 (FKBP51) is a negative regulator of the glucocorticoid receptor signaling pathway that regulates the stress-induced glucocorticoid feedback circuit. Here we asked whether selective inhibitors of FKBP51, exemplified by SAFit2, may serve as a new pharmacological strategy to reduce alcohol consumption and conditioned alcohol effects in a mouse model. We report that a relatively short treatment with SAFit2 (20 mg/kg, ip) reduces ongoing 16 vol% alcohol consumption when administered during free access to alcohol in a two-bottle freechoice test. SAFit2 was also able to reduce alcohol consumption when given during an abstinence period immediately before relapse. In contrast, SAFit2 did not affect alcohol consumption when given during a relapse period after repeated withdrawal from alcohol. SAFit2 (10 and 20 mg/kg, ip) showed no effects when used in an intermittent drinking schedule. When 20 vol% alcohol was only available every other day, SAFit2 had no effect on drinking, no matter whether given during a drinking episode or the day before. SAFit2 (2 and 20 mg/kg, ip) did not affect the expression of an alcohol-induced conditioned place preference (CPP). However, SAFit2 was able to inhibit alcohol-induced reinstatement of an extinguished CPP in a dose-dependent way. Altogether, these data may suggest pharmacological inhibition of FKBP51 as a viable strategy to reduce alcohol seeking and consumption.

Pseudoexfoliation (PEX) syndrome, a stress-induced fibrotic matrix process, is the most common recognizable cause of open-angle glaucoma worldwide. The recent identification of PEX-associated gene variants uncovered the vitamin A metabolic pathway as a factor influencing the risk of disease. In this study, we analyzed the role of the retinoic acid (RA) signaling pathway in the PEX-associated matrix metabolism and evaluated its targeting as a potential candidate for an anti-fibrotic intervention. We provided evidence that decreased expression levels of RA pathway components and diminished RA signaling activity occur in an antagonistic crosstalk with TGF-β1/Smad signaling in ocular tissues and cells from PEX patients when compared with age-matched controls. Genetic and pharmacologic modes of RA pathway inhibition induced the expression and production of PEX-associated matrix components by disease-relevant cell culture models in vitro. Conversely, RA signaling pathway activation by natural and synthetic retinoids was able to suppress PEX-associated matrix production and formation of microfibrillar networks via antagonization of Smad-dependent TGF-β1 signaling. The findings indicate that deficient RA signaling in conjunction with hyperactivated TGF-β1/Smad signaling is a driver of PEX-associated fibrosis, and that restoration of RA signaling may be a promising strategy for anti-fibrotic intervention in patients with PEX syndrome and glaucoma.

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