Human PER1 blocking peptide

Many studies suggest that the prefrontal cortex (PFC) is a target limbic region for stress response because a dysfunction here is linked to anhedonia, a decrease in reactivity to rewards, and to anxiety. It is suggested that stress-induced persistent molecular changes in this brain region could bring some light on the mechanisms perpetuating depressive episodes. In order to address this issue, here we have studied the long-term PFC gene expression pattern and behavioral effects induced by a chronic mild stress (CMS) model and antidepressant treatment in mice. CMS was applied to mice for six weeks and imipramine (10 mg/kg, i.p.) or saline treatment was administered for five weeks starting from the third week of CMS. Mice were sacrificed one month after CMS and following two weeks after the discontinuation of drug treatment and the PFC was dissected and prepared for gene (mRNA) and protein expression studies. Using the same experimental design, a separate group of mice was tested for anhedonia, recognition memory, social interaction and anxiety. CMS induced a long-term altered gene expression profile in the PFC that was partially reverted by imipramine. Specifically, the circadian rhythm signaling pathway and functions such as gene expression, cell proliferation, survival and apoptosis as well as neurological and psychiatric disorders were affected. Of these, some changes of the circadian rhythm pathway (Hdac5, Per1, and Per2) were validated by RT-PCR and western-blot. Moreover, CMS induced long-lasting anhedonia that was reverted by imipramine treatment. Impaired memory, decreased social interaction and anxiety behavior were also induced by chronic stress. We have identified in the PFC molecular targets oppositely regulated by CMS and imipramine that could be relevant for chronic depression and antidepressant action. Among these, a possible candidate for further investigation could be the circadian rhythm pathway. (C) 2015 Elsevier Inc. All rights reserved.

Cryptochrome (Cry) 1 and 2 are essential for circadian rhythm generation, not only in the suprachiasmatic nucleus, the site of the mammalian master circadian clock, but also in peripheral organs throughout the body. CRY is also known as a repressor of arylalkylamine-N-acetyltransferase (Aanat) transcription; therefore, Cry deficiency is expected to induce constantly high pineal melatonin content. Nevertheless, we previously found that the content was consistently low in melatonin-proficient Cry1 and Cry2 double-deficient mice (Cry1(-/-)/Cry2(-/-)) on C3H background. This study aims to clarify the mechanism underlying this discrepancy. In the Cry1(-/-)/Cry2(-/-) pineal, expression levels of Aanat and clock gene Per1 were consistently high with no circadian fluctuation on the first day in constant darkness, demonstrating that CRY acts in vivo as a repressor of the pineal circadian clock and AANAT. In contrast, the enzyme activity and protein levels of AANAT remained low throughout the day, supporting our previous observation of continuously low melatonin. Thus, effects of Cry deficiency on the responses of beta-adrenergic receptors were examined in cultured pineal glands. Isoproterenol, a beta-adrenergic stimulant, significantly increased melatonin content, although the increase was smaller in Cry1(-/-)/Cry2(-/-) than in WT mice, during both the day and night. However, the increase in cAMP in response to forskolin was similar in both genotypes, indicating that CRY deficiency does not affect the pathway downstream of the beta-adrenergic receptor. These results suggest that a lack of circadian adrenergic input due to CRY deficiency decreases beta-receptor activity and cAMP levels, resulting in consistently low AANAT levels despite abundant Aanat mRNA.