Pifithrin-μ Attenuates Acute Sickness Response to Lipopolysaccharide in C57BL/6J Mice

Sickness behavior is a coordinated set of behavioral changes that happen as a response to acute infectious pathogens. Its well-known benefit is to reorganize the organism's priorities to cope with infection, but the uncontrolled development of sickness behavior may trigger negative feelings or chronic depressive events. This study aims at investigating the potential effect of pifithrin-μ, an inhibitor of heat shock protein 70 substrate binding activity, on lipopolysaccharide (LPS)-induced sickness response. C57BL/6J mice were submitted to the forced swimming test (FST), tail suspension test (TST), open field test (OFT) and light-dark box test. Food intake and body weight were also evaluated. The serum corticosterone level was measured using an ELISA kit. Treatment of mice with LPS (0.33 mg/kg, i.p.) markedly increased the floating and immobility time in the FST and TST, respectively, and depressed locomotor activity in the OFT. LPS administration prolonged the latency to first transition and reduced the total number of transitions in the light-dark box test. In addition, LPS induced anorexia and increased serum corticosterone levels. Pretreatment with pifithrin-μ (1 or 5 mg/kg) attenuated behavioral changes induced by LPS in the FST, TST, OFT and light-dark box test. Pifithrin-μ also prevented the formation of anorexia as well as the increase in serum corticosterone levels in LPS-treated mice. Our previous studies showed that pifithrin-μ prevents the production of pro-inflammatory factors in both microglia and macrophages. These findings presented here extend the role of pifithrin-μ beyond an anti-inflammatory molecule to a modulator of sickness behavior.