Stress enhances expression of calcium-binding proteins and NMDAR subunit genes in the rat hippocampus

Backgrounds:Oxidative stress impairs the function of calcium-binding proteins and deregulates calcium signaling in living organisms.We have previously explored the overexpression of calcium-binding protein genes in a reactive oxygen and nitrogen species-induced in vitro cell model of stress that leads to apoptosis.However,in in vivo models,low levels of stress leads to depressive-like behavior.Here,we aimed to analyze gene expression of major calcium-binding proteins(calcineurin,calmodulin,calsyntenin,synaptotagmin,and calreticulin)and N-methyl-D-aspartic acid(NMDA)receptor subunits(glutamate receptor ionotropic[GluN]GluN1,GluN2A,and GluN2B)in the hippocampus of stress-induced rats.Methods:Six-week-old male Wistar rats were assigned to two stress induction groups and a control group without stress(n=6).Stress was induced by using H_(2)O_(2)(3%in water)or by immobilization(using a sticky mat)over a period of 30 days.Expression of calcium-binding protein genes in the hippocampus,antioxidant assays,structural alterations in hippocampal neurons,and depressive-like behavior were determined.Results:Expression of genes encoding calcium-binding proteins calcineurin,calsyntenin,synaptotagmin and NMDA receptor subunit GluN1 was enhanced in both chemical and physical stress-induced rats compared with control rats(4.25±0.05 vs.1.03±0.02,p<0.05,2.05±0.08vs.1.03±0.02,p<0.005;2.2±0.4 vs.1.02±0.03,p<0.05,1.98±0.07 vs.1.02±0.03,p<0.005;1.4±0.6 vs.1.15±0.09,p<0.05,1.39±0.05 vs.1.15±0.09,p<0.005),respectively.In stress-induced rats,neurons in the CA2 region of the hippocampus were fewer and appeared disorganized compared with control rats.Furthermore,stressinduced rats showed decreased mobility and lower sucrose preference in behavioral studies compared with control rats.Conclusion:Lower levels of reactive oxygen and nitrogen species(RONS)can also lead to stress in rats by affecting their calcium signaling,buffering capacity in the neurons leading to depressive symptoms.

Elevation of gene expression of calcineurin,calmodulin and calsyntenin in oxidative stress induced PC12 cells

In normal physiological conditions,reactive oxygen and nitrogen species are used as important signaling molecules in the cell.However,in excess it causes the disruption of cell resulting in their death.Oxidative stress causes influx in intracellular calcium levels leading to higher concentrations of calcium in the cell.This accelerated calcium affects both the mitochondria and nuclei leading to excitotoxicity in neurons.Intracellular calcium levels are controlled by voltage dependent calcium channels located in the plasma membrane,calcium stores like endoplasmic/sarcoplasmic reticulum and majorly by calcium binding proteins.Our study was aimed at analyzing the gene expression of major calcium binding proteins namely calcineurin,calmodulin,calreticulin,synaptotagamin and calsyntenin in stress induced PC 12 cells.Rotenone(1 mM),Peroxynitrite(10 mM),H_(2)O_(2)(100 mM)and High glucose(33 mM)were used to induce oxidative stress in PC12 cells.Results obtained from the study suggest that calcineurin,calmodulin and calsyntenin gene expression were enhanced compared to the control due to oxidative stress.However,synaptotagmin and calreticulin gene expression were down regulated.Further,Akt protein expression(stress marker)was enhanced in PC12 cells with all other stress inducers except in hyperglycemic condition.