Depression is an independent risk factor for cardiovascular disease. Reduced NO (Nitric Oxide) bioavailability is considered to be one mechanism linking depression to CVD. Oxidative stress can reduce NO bioavailability. Oxidative stress produce Reactive Oxygen Species (ROS) .Usual antioxidants who neutralise ROS include antioxidant enzymes ( copper-zinc superoxide dismutase (SOD), catalase and glutathione peroxidase) and non-enzymatic antioxidants (like bilirubin, uric acid, glutathione, and vitamins A, C, and E) . ROS have direct effects on platelets. ROS can also reduce NO.
Depressed individuals show heightened level of platelet activation.Platelet dysfunction is a possible mechanism through which depression may increase cardiovascular risk
Monique B.O. Ormonde do Carmo et al studied the factors that modulate NO bioavailability and platelet dysfunction in depression.
Treatment naive major depression patients and controls participated in this study. Platelet aggregation, ,oxidative state and antioxidant enzyme activities were studied.
Platelet aggregation was higher in depression group.
Depression group showed higher activity of arginase II in platelets. Activation of the arginase can shift L-arginine to the urea cycle rather than to NO synthesis. ( resulting in less NO)
MDD patients has higher PDE5 expression. NO regulate cyclic GMP levels in platelet and this play a key role in platelet activity. PDE5 is responsible for breakdown of CGMP. Over expression of PDE5 would thus result in increased degradation of cGMP. cGMP signalling can thus be down regulated leading to platelet reactivity.
Indicator of oxidative damage ( =protein carbonylation) was markedly increased in platelets in MDD
Limitations: Small study.Cross sectional in nature.
Comments: Psychological states/ conditions exert significant effect on physical health. Knowledge on biological pathways that link them is expanding. These are building blocks for understanding the interplay between mind, body, and society .
Summary of the article
Ormonde do Carmo MB, Mendes-Ribeiro AC, Matsuura C, Pinto VL, Mury WV, Pinto NO, Moss MB, Ferraz MR, Brunini TM.
J Psychiatr Res. 2015 Feb;61:19-24