Hippocampal prosaposin changes during stress: a glucocorticoid-independent event

Plasma proteomic signature of chronic psychosocial stress in mice

Chronic stress significantly impacts both physical and mental wellbeing, increasing risk of cardiovascular disease, immune dysregulation, and psychiatric conditions such as depression and anxiety disorders. The plasma proteome is a valuable source of biomarkers of health and disease, but the limited number of studies exploring the potential of the plasma proteome as a biomarker for stress-related disorders underscores the importance of further investigation of the effects of chronic stress on the plasma proteome. The aim of this study was to examine the effect of a 5-week chronic psychosocial stress paradigm on the plasma proteome in mice and to determine if any affected proteins correlated with stress-induced changes in behaviour and physiology, and thus might represent biomarkers of negative impacts of chronic stress. Using LC-MS/MS proteomic analysis, 38 proteins in the mouse plasma proteome were identified to be affected by chronic psychosocial stress. Functional analysis revealed that these proteins clustered into biological functions including inflammatory response, regulation of the immune response, complement and coagulation cascades, lipid metabolic process, and high-density lipoprotein particles. Correlation analyses of the identified proteins with stress-induced behavioral or physiological changes stress revealed significant correlations between stress-induced anxiety-like behaviour and Phosphatidylinositol-glycan-specific phospholipase D, Complement C2, Epidermal growth factor receptor, Prosaposin, Actin-related protein 2/3 complex subunit 1B, Maltase-glucoamylase, Mannosyl-oligosaccharide 1,2-alpha-mannosidase IA and Fibrinogen-like protein 1. Chronic psychosocial stress blunted acute stress-induced corticosterone release, and this correlated with abundance of Pyrethroid hydrolase Ces2a; N-fatty-acyl-amino acid synthase/hydrolase Pm20d1, Mannosyl-oligosaccharide 1,2-alpha-mannosidase IA, Alpha-2-macroglobulin-P and L-selectin. Finally, stress-induced reductions in both brown and epididymal fat correlated with Phosphatidylinositol-glycan-specific phospholipase D, Complement C2, Epidermal growth factor receptor, Kininogen-1, Apolipoprotein M, Angiopoietin-related protein 3, Proprotein convertase subtilisin/kexin type 9, and Lipopolysaccharide-binding protein. These findings demonstrate that chronic psychosocial stress induces alterations in plasma proteins implicated in key biological processes and pathways related to stress response, immune function, and lipid metabolic regulation. Further investigation into these proteins may provide new avenues for identification of biomarkers or mediators of stress-induced pathology.

Stress and corticosterone alter synaptic plasticity in a rat model of Parkinson's disease

As a major influence on neuronal function and plasticity, chronic stress can affect the progression and symptoms of neurodegenerative conditions, such as Parkinson's disease (PD). Here we investigated the influence of unilateral dopamine depletion and stress on dopamine-related hallmarks of stress response and neuronal plasticity in a rat model of PD. Animals received either restraint stress or a combination of adrenalectomy and corticosterone (CORT) supplementation to clamp circulating glucocorticoid levels for three weeks prior to unilateral nigrostriatal dopamine depletion. Rats were tested in skilled and non-skilled motor function up to three weeks post-lesion. Midbrain mRNA expression assessments included markers of dopamine function and neuroplasticity, such as tyrosine hydroxylase (TH), synaptophysin (SYN), calcyon, and glucocorticoid receptor (GR). Along with impaired motor performance, stress and clamped CORT partially preserved TH expression in both substantia nigra (SN) and ventral tegmental area (VTA), but differentially modulated the expression of SYN, calcyon, and GR mRNA in midbrain and cortical areas. Stress reduced synaptophysin mRNA expression in SN/VTA, and elevated calcyon mRNA optical density in both non-lesion and lesion hemispheres. Stress and CORT increased GR mRNA in the non-lesion SN/VTA, while in the lesion hemisphere GR mRNA was only elevated by CORT. In the motor cortex and striatum, however, GR was higher in both hemispheres under both experimental conditions. These findings suggest that stress and stress hormones differentially affect dopaminergic function and neuroplasticity in a rat model of PD. The findings suggest a role for stress in motor and non-motor symptoms of PD and stress response.

Effect of stress on hippocampal nociceptin expression in the rat

Nociceptin/orphanin FQ (N/OFQ) peptide and its receptor are not only ubiquitously expressed in mammalian brain and spinal cord but are also abundant in limbic structures, particularly in the hippocampus. The widespread distribution of N/OFQ reflects the broad spectrum of its biological actions such as nociception, food intake, spontaneous locomotor activity, and learning and memory processes. Since the hippocampus is involved in the control of adrenocortical activity, its role in stress-related phenomena is well characterized. In male Wistar rats, we first examined the effects of acute restraint stress (120 min) on the brain immunohistochemical localization of N/OFQ. The analysis carried out on sections obtained at the onset of stress revealed enhanced expression of N/OFQ in CA1, CA3, and the dentate gyrus as well as increased plasma corticosterone concentrations. Next, we examined whether endogenous glucocorticoid hormone plays a role in the modulation of hippocampal N/OFQ expression in response to stress. To this end, rats were injected with corticosterone (1 mg/kg) or subjected to restraint stress 1 week after adrenalectomy. Two hours after corticosterone administration, plasma glucocorticoid concentrations were comparable to those observed after restraint stress, while N/OFQ expression had significantly increased in all the hippocampal subfields examined. By contrast, in adrenalectomized rats, stress did not modify protein expression. These results confirm that stress can affect N/OFQ expression and that glucocorticoids may constitute hormonal mediators of this complex interplay.

Regional expression of prosaposin in the wild-type and saposin D-deficient mouse brain detected by an anti-mouse prosaposin-specific antibody

Prosaposin is a precursor of saposins A, B, C, and D. Saposins are indispensable for lysosomal hydrolysis of sphingolipids. The notion that prosaposin itself is likely involved in brain development led us to generate an anti-mouse prosaposin-specific antibody that do not cross-react with any of the processed saposins. We have used it to study expression of prosaposin in the brain of wild-type (WT) and saposin D knockout mice (Sap-D(-/-)). Immunoblot studies indicated that prosaposin, already abundant in the brain of WT, was dramatically increased in Sap-D(-/-). By immunohistochemistry, the brain of WT was rich in prosaposin in hippocampal CA3 pyramidal neurons, tufted cells and mitral cells in olfactory bulb, and cerebellar Purkinje cells. In Sap-D(-/-), immunoreactivity of prosaposin was increased in these neurons, most notably in the CA3 pyramidal neurons which contained prosaposin immuno-positive inclusion bodies in the endoplasmic reticulum. Further characterization of these prosaposin-rich neurons may provide new insights into the physiological functions of prosaposin in the nervous system.

Stress accelerates neural degeneration and exaggerates motor symptoms in a rat model of Parkinson's disease

The causes of most cases of Parkinson's disease (PD) are still poorly understood. Here we show that chronic stress and elevated corticosterone levels exaggerate motor deficits and neurodegenerative events in a Parkinson's disease rat model. Animals were tested in skilled and non-skilled movement while being exposed to daily restraint stress or oral corticosterone treatment. Stress and corticosterone compromised normal motor function and exaggerated motor deficits caused by unilateral 6-hydroxydopamine lesion of the nigrostriatal bundle. Moreover, stress and corticosterone treatments diminished the ability to acquire compensatory strategies in limb use during skilled reaching and skilled walking. In contrast, lesion control animals were able to significantly improve in the ability of skilled limb use during the repeated test sessions. The exaggerated motor impairments in stress-treated animals were related to accelerated loss of midbrain dopamine-producing neurons during the first week postlesion. Correlation analysis revealed a significant connection between loss of tyrosine hydroxylase-positive cells and increase in Fluoro-Jade-positive cells only in stress- and corticosterone-treated animals. Furthermore, stress and elevated corticosterone levels caused greater permanent loss of midbrain neurons than found in non-treated lesion animals. These findings demonstrate that stress and elevated corticosterone levels can exaggerate nigral neuronal loss and motor symptoms in a rat analogue of PD. It is therefore possible that stress represents a key factor in the pathogenesis of human PD by impeding functional and structural compensation and exaggerating neurodegenerative processes.