Reducing PRLR expression and JAK2 activity results in an increase in BDNF expression and inhibits the apoptosis of CA3 hippocampal neurons in a chronic mild stress model of depression

Abstract

Patients suffering from depression most commonly present with symptoms associated with the autonomic nervous system. Despite the satisfactory results achieved following treatment with vagus nerve stimulation and drug treatment, recurrence is a common occurrence in many patients. As described in numerous studies, prolactin receptor (PRLR) has been identified as an anxiolytic and anti-depressant factor in depression. However, the effect of PRLR on chronic mild stress (CMS)-induced depression remains to be thoroughly demonstrated. Therefore, the present study was conducted on the effect of PRLR gene on brain derived neurotrophic factor (BDNF) expression and hippocampal neuron apoptosis through the establishment of CMS-induced depression mouse models, with aims of providing a new and effective therapeutic option for depression. Microarray-based analysis was initially used to retrieve depression-related expression dataset and PRLR-related signaling pathway. Lentiviral vectors overexpressing PRLR or expressing PRLR-specific shRNA were used to up- or down-regulated the expression of PRLR in mice. Subsequently, the effects of PRLR on hippocampal neurons and pyramidal cells in CA1 and CA3 regions, and ultrastructure in hippocampal region were evaluated. Serum BDNF level and the positive rate of cleaved-Caspase-3 in hippocampal CA3 region were determined. Next, the regulatory mechanism by which PRLR gene silencing influences hippocampal neuron apoptosis via the JAK2-STAT5 signaling pathway was detected. PRLR gene was assumed to participate in the development of depression by regulating the JAK-STAT signaling pathway. Our results found that the mice with CMS-induced depression exhibited locomotion activity and anhedonia. In addition, a decrease in the number of pyramidal cells was observed in the hippocampus while that of apoptotic cells was increased. In addition, serum BDNF level was increased, and the expression of Caspase-3 and Bax in hippocampal neurons and the JAK2-STAT5 signaling pathway was decreased in response to PRLR silencing, along with increased expression of BDNF and Bcl-2. From the aforementioned findings, we concluded that PRLR gene silencing results in the inhibition of hippocampal neuron apoptosis and alleviation of CMS-induced depression by inactivating the JAK2-STAT5 signaling pathway and elevating BDNF expression, providing a new insight for the treatment of depression.

Keywords: Apoptosis; Brain derived neurotrophic factor; Depression; Hippocampal neurons; JAK2-STAT5 signaling pathway; Prolactin receptor.