Abstract:
Depression is associated with dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis, sympathetic hyperactivity, and inflammation. This neurohumoral dysregulation in depressive patients causes ae greater risk of cardiovascular disease. It has been suggested that treatment of depression may be achieved by combining NSAID (COX-2 inhibitor) with a typical antidepressant. However, it has not yet been examined the cardiovascular risk of the combination therapy. This study was performed to assess the effects of fluoxetine (serotonin reuptake inhibitor) in conjuction with celecoxib on cardiovascular risk in depressive rats induced by chronic mild stress (CMS). The rats were divided into 4 groups: 1) control, 2) CMS, 3) CMS with fluoxetine treatment (5 mg/kg/d), and 4) CMS with fluoxetine and celecoxib treatment (5 mg/kg/d each). The rats were subjected to CMS and the drug treatment for 5 weeks. At the end of the treatment, the following parameters were examined: depressive sign using force swimming test, plasma cortisol, body weight gain, plasma inflammatory mediators (PGE2, IL-1, TNF- and CRP), plasma MAD (oxidative stress marker), blood pressure, arterial stiffness by measuring pulse wave velocity (PWV), SDNN index (representing heart rate variability, HRV) calculated from the pulse wave, and in vitro vascular reactivity. The study reveals the following findings. 1) Either fluoxetine treatment or in combination with celecoxib alleviated the depressive sign in a comparable degree. The combined drugs caused a slightly increase in plasma cortisol compared with fluoxetine alone, indicating a greater activation of the HPA axis. Celecoxib co-treatment also resulted in a slightly greater body weight gain, suggesting edema due to body fluid retention. 2) Depressive rats showed increases in plasma inflammatory mediators. Fluoxetine treatment partially lowered PGE2 and CRP, and fully recovered plasma TNF-, but showed no significant effect on plasma IL-1. Drug combination decreased plasma PGE2, TNF- and CRP in the same extent as fluoxetine treatment, but completely returned plasma IL-1. However, the plasma levels of inflammatory mediators in both treatments were still higher than those of control. 3) Depressive rats showed an increase in plasma MAD, indicating an existence of oxidative stress in depressive state. Fluoxetine treatment significantly decreased plasma MAD, whereas drug combination showed a lesser extent in antioxidant activity. Both drug treatments exhibited only a moderate degree of antioxidant properties and could not eradicate oxidative stress. 4) CMS induced depression caused a decrease in SDNN index (HRV), and fluoxetine exerted no significant effect on this parameter. In contrast, fluoxetine with celecoxib produced increased SDNN index, suggesting a higher ability of cardiac autonomic nervous system to keep homeostasis against stress challenges. 5) The PWVs were not altered by either fluoxetine alone or combined drug treatment, suggesting that arterial stiffness may not be evident in the five-week period of both drug treatments. 6) CMS-induced depression produced an increase in systolic blood pressure which was attenuated by fluoxetine treatment. However, co-treatment with celecoxib caused a rebound of blood pressure to the level higher than those of fluoxetine alone. 7) The responses of aortas from depressive rats to vasoconstrictor phenylephrine (PE,1-adrenergic receptor agonist) were not altered, whereas responses to vasodilator isoproterenol (Iso, -adrenergic receptor agonist) and acetylcholine (ACh, muscarinic receptor agonist) decreased significantly. Fluoxetine treatment caused a slight decrease in aortic responses to PE, whereas it was unable to recover vascular response to Iso and ACh. The combined drug treatment tended to elevate aortic response to PE slightly and fully returned the responses to Iso, but partially recovered the aortic responses to ACh indicating that endothelial dysfunction still existed. In conclusions, this study provides evidence that the add-on celecoxib to fluoxetine is not superior to fluoxetine alone in their antidepressant effect. Moreover, drug combination increases the blood pressure which is associated with body fluid retention and endothelial dysfunction. The higher levels of plasma inflammatory mediators and the greater degree of oxidative stress in both treatments may cause futher vascular damage.