Protective effect of sex on chronic stress- and depressive behavior-induced vascular dysfunction in BALB/cJ mice

Abstract

The presence of chronic, unresolvable stresses leads to negative health outcomes, including development of clinical depression/depressive disorders, with outcome severity being correlated with depressive symptom severity. One of the major outcomes associated with chronic stress and depression is the development of cardiovascular disease (CVD) and an elevated CVD risk profile. However, in epidemiological research, sex disparities are evident, with premenopausal women suffering from depressive symptoms more acutely than men, but also demonstrating a relative protection from the onset of CVD. Given this, we investigated the differential effect of sex on conduit artery and resistance arteriolar function in male and female mice following 8 wk of an unpredictable chronic mild stress (UCMS) protocol. In males, plasma cortisol and depressive symptom severity (e.g., coat status, anhedonia, delayed grooming) were elevated by UCMS. Endothelium-dependent dilation to methacholine/acetylcholine was impaired in conduit arteries and skeletal muscle arterioles, suggesting a severe loss of nitric oxide bioavailability and increased production of thromboxane A2 vs. prostaglandin I2 associated with elevated reactive oxygen species (ROS) and an increased level of systemic inflammation. Endothelium-independent dilation was intact. In females, depressive symptoms and plasma cortisol increases were more severe than in males, although alterations to vascular reactivity were blunted, including the effects of elevated ROS and inflammation on dilator responses. These results suggest that compared with males, female rats are more susceptible to chronic stress in terms of the severity of depressive behaviors, but that the subsequent development of vasculopathy is blunted owing to an improved ability to tolerate elevated ROS and systemic inflammatory stress.

Keywords: clinical depression; endothelium-derived factors; models of chronic stress; nitric oxide; peripheral vascular disease; vasodilation.

Fig. 1.

Depressive symptoms following 8 wk of the unpredictable chronic mild stress (UCMS) protocol in male and female BALB/cJ mice. Data are presented for coat status (A), latency (B), and frequency (C) of facial grooming following a 10% sucrose solution spray, and the total period of immobility during the tail suspension test (D) for control and UCMS mice. Control males n = 14; control females n = 9; UCMS males n = 12; UCMS females n = 12. *P < 0.05 vs. control in the sex; †P < 0.05 vs. UCMS male.

Fig. 2.

Constrictor responses of aortic rings to increasing concentrations of phenylephrine from mice under control conditions and after 8 wk of UCMS. Data are presented under untreated conditions (A) and in response to nitric oxide synthase inhibition with N^G-nitro-l-arginine methyl ester (l-NAME) (B). Control males n = 12; control females n = 8; UCMS males n = 10; UCMS females n = 10.

Fig. 3.

Dilator responses of aortic rings to increasing concentrations of methacholine from mice under control conditions and after 8 wk of UCMS. A: untreated conditions. B and C: dilator responses from male and female control mice, respectively, following pretreatment with l-NAME, indomethacin (INDO) or a combination of these. D and E: dilator responses from male and female UCMS mice, respectively, following pretreatment with l-NAME, INDO, or a combination. Control males n = 6–9; control females n = 5–7; UCMS males n = 8–10; UCMS females n = 7–10. *P < 0.05 vs. responses in untreated vascular rings from control mice of that sex; †P < 0.05 vs. responses in untreated vascular rings from UCMS male mice.

Fig. 4.

Dilator responses of aortic rings to increasing concentrations of sodium nitroprusside from mice under control conditions and after 8 wk of UCMS. Control males n = 10; control females n = 8; UCMS males n = 9; UCMS females n = 9.

Fig. 5.

Vascular production of nitric oxide (A), prostaglandin I₂ (PGI₂) (B; estimated from 6-keto-PGF_1α), and thromboxane A₂ (TxA₂) (C; estimated from 11-dehydro-TxB₂) following methacholine challenge in mice under control conditions and following 8 wk of UCMS. Control males n = 9; control females n = 7; UCMS males n = 8; UCMS females n = 8. *P < 0.05 vs. responses in vessels from control mice; †P < 0.05 vs. responses in vessels from UCMS males.

Fig. 6.

Vascular production of nitric oxide (NO) following methacholine challenge in male and female mice following 8 wk of UCMS. Data are presented for vessels under control (untreated) conditions, following treatment of vessels from UCMS animals with TEMPOL and following treatment of vessels from UCMS animals with l-NAME. Control males n = 9; control females n = 7; UCMS males n = 8; UCMS females n = 8. *P < 0.05 vs. responses in control vessels from mice of that sex; †P < 0.05 vs. responses in untreated vessels of UCMS mice of that sex; ‡P < 0.05 vs. responses in UCMS + TEMPOL-treated mice of that sex.

Fig. 7.

Dilator responses of aortic rings to increasing concentrations of methacholine from UCMS male (A) and UCMS female (B) mice. A: UCMS males under untreated conditions, following pretreatment with TEMPOL, following treatment with TEMPOL/INDO, and following treatment with TEMPOL/l-NAME. B: UCMS females under untreated conditions, following pretreatment with TEMPOL, following treatment with TEMPOL/INDO, and following treatment with TEMPOL/l-NAME. Control males n = 8–11; control females n = 7–9; UCMS males n = 8–9; UCMS females n = 7–9. *P < 0.05 vs. responses in untreated vessels; †P < 0.05 vs. responses in vessels that were pretreated with TEMPOL.

Fig. 8.

Constrictor responses of gracilis arterioles to increasing concentrations of phenylephrine from mice under control conditions and after 8 wk of UCMS. Data are presented under control conditions (A) and in response to nitric oxide synthase (NOS) inhibition with l-NAME (B). Control males n = 10; control females n = 8; UCMS males n = 10; UCMS females n = 10. *P < 0.05 vs. responses in arterioles from control mice.

Fig. 9.

Dilator responses of gracilis arterioles to increasing concentrations of acetylcholine from mice under control conditions and after 8 wk of UCMS. A: male mice under untreated conditions and following pretreatment with l-NAME or INDO. B: male mice after pretreatment with TEMPOL alone or with l-NAME. C: female mice under untreated conditions and following pretreatment with l-NAME or INDO. D: female mice after pretreatment with TEMPOL alone or with l-NAME. Control males n = 8–10; control females n = 7–8; UCMS males n = 9–10; UCMS females n = 8–10. *P < 0.05 vs. responses in vessels from control mice of that sex; †P < 0.05 vs. responses in vessels from UCMS mice of that sex.

Fig. 10.

Correlations between vascular reactivity and individual markers of chronic inflammation in control male (blue), control female (red), UCMS male (green), and UCMS female (black) mice. Data are presented as the lower bound of the methacholine concentration-response curve for an individual aortic ring vs. plasma concentrations of tumor necrosis factor-α (TNF-α) (A) or monocyte chemoattractant protein-1 (MCP-1) (B). In this figure, the lower bound from methacholine concentration-response curve is reflective of the degree of dilator reactivity for that vessel. If the vessel is more reactive to methacholine, the lower bound is decreased, whereas if the vessel becomes less reactive, the lower bound is increased. Also presented are lines of best fit through the data for each group, with the resulting slope (β) and r² values presented in the legend.