Transient angiotensin-converting enzyme (ACE) inhibition induces persistent changes that protect against future nitric oxide synthase (NOS) inhibitor-induced cardiac fibrosis and inflammation. Given the role of fibroblasts in mediating these effects, the present study investigates whether prior ACE inhibition produced persistent changes in cardiac fibroblast physiology. Adult male spontaneously hypertensive rats (SHRs) were treated with vehicle (C+L) or the ACE inhibitor, enalapril (E+L) for 2 wk followed by a 2-wk washout period and a subsequent 7-day challenge with the NOS inhibitor N(ω)-nitro-l-arginine methyl ester. A third set of untreated SHRs served as controls. At the end of the study period, cardiac fibroblasts were isolated from control, C+L, and E+L left ventricles to assess proliferation rate, collagen expression, and chemokine release in vitro. After 7 days of NOS inhibition, there were areas of myocardial injury but no significant change in collagen deposition in E+L and C+L hearts in vivo. In vitro, cardiac fibroblasts isolated from C+L but not E+L hearts were hyperproliferative, demonstrated increased collagen type I gene expression, and an elevated secretion of the macrophage-recruiting chemokines monocyte chemoattractant protein-1 and granulocyte macrophage-colony stimulating factor. These findings demonstrate that in vivo N(ω)-nitro-l-arginine methyl ester treatment produces phenotypic changes in fibroblasts that persist in vitro. Moreover, this is the first demonstration that transient ACE inhibition can produce a persistent modification of the cardiac fibroblast phenotype to one that is less inflammatory and fibrogenic. It may be that the cardioprotective effects of ACE inhibition are related in part to beneficial changes in cardiac fibroblast physiology.

Vascular basal cyclooxygenase-2 (COX-2) expression and activity can be induced by endotoxin, hypoxia, or ischemia. During vascular pathologies such as atherosclerosis, increases in COX-2 activity result in prostanoid production, a contributor to the development and progression of vascular inflammation leading to unstable atherosclerotic plaques and increased risk for thrombotic events. Recent studies demonstrate that select free fatty acids, such as palmitate, can act as proinflammatory mediators. However, the effect of palmitate on COX-2 expression and activity, and its impact on the development and progression of vascular inflammation, are not well elucidated. We investigated the effect of palmitate on COX-2 expression and function in human vascular smooth muscle cells. Cells were treated with palmitate, COX-2 protein levels were assessed using Western analysis, and activity was assessed via ELISA. We observed that palmitate dose-dependently increased COX-2 levels and specifically enhanced band intensity of the COX-2 74 kDa band (slowest migrating band). This response was attenuated by N-linked glycosylation inhibition, suggesting that palmitate impacts expression of the fully activated glycoform of COX-2. Palmitate-induced increases in COX-2 levels correlated with an increase in prostaglandin E production that was also attenuated by a glycosylation inhibitor. Additionally, palmitate altered cell morphology and increased cell density which were reversed by selective COX-2 inhibition. Thus, we conclude that palmitate acts on COX-2 by two separate mechanisms of action in human vascular smooth muscle. It elicits dose-dependent increases in COX-2 protein expression and modulates regulation of COX-2 activity via modification of posttranslational glycosylation.

In utero exposure to glucocorticoids in late gestation programs changes in cardiovascular function. The objective of this study was to determine the degree to which angiotensin II mediates sex-biased changes in autonomic function as well as basal and stress-responsive cardiovascular function following in utero glucocorticoid exposure. Pregnant rats were administered the synthetic glucocorticoid dexamethasone (DEX 0.4mg/kg per day, s.c.) or vehicle on gestation days 18-21. Mean arterial pressure, heart rate, and heart rate variability (HRV) were measured via radiotelemetry in freely moving, conscious adult rats. To evaluate the impact of stress, rats were placed in a restraint tube for 20 minutes. In a separate cohort of rats, restraint stress was performed before and after chronic treatment with the angiotensin type 1 receptor antagonist, losartan (30mg/kg per day, i.p). Frequency domain analysis of HRV was evaluated, and data integrated into low frequency (LF: 0.20-0.75Hz) and high frequency (HF: 0.75-2.00Hz) bands. Prenatal DEX resulted in an exaggerated pressor and heart rate response to restraint in female offspring that was attenuated by prior losartan treatment. HF power was higher in vehicle-exposed female rats, compared to DEX females. Following losartan, HF power was equivalent between female vehicle and DEX-exposed rats. In utero exposure to DEX produced female-biased alterations in stress-responsive cardiovascular function which may be indicative of a reduction in parasympathetic activity. Moreover, these findings suggest this autonomic dysregulation may be mediated in part by long-term changes in renin-angiotensin signaling.

It is well established that even transient prenatal insults can impact cardiovascular (CV) function in adulthood. We hypothesized that adult CV disease may have its origins in utero as a result of exposure to elevated levels of glucocorticoids arising as a result of prenatal stress or inflammation. In support of this, we showed that when pregnant rat dams are treated with the synthetic glucocorticoid, dexamethasone (DEX), for 4 days in late gestation, there are female‐specific changes resulting in enhanced pressor and tachycardic responses to stress in adult offspring. We further showed that these effects in DEX exposed females can be reversed following treatment with the angiotensin II type 1 receptor antagonist, losartan. To better understand whether autonomic imbalance drives the sex‐specific CV effects of adult offspring prenatally exposed to DEX, we investigated the impact of DEX on heart rate variability (HRV). Pregnant dams were administered DEX (0.4mg/kg per day, s.c.) or vehicle on gestation days 18–21. This resulted in a significant reduction in birthweight in DEX‐exposed males and females. At 2–3 months of age, rats were instrumented with radiotelemetric transmitters for direct recording of arterial pressure, heart rate, and HRV. In a separate cohort, female rats were re‐evaluated following 9 days of losartan (30mg/kg per day, i.p.). HRV was analyzed in the frequency domain by obtaining arterial pressure waveforms recorded over 2–3 days. Interbeat intervals were analyzed (Kubios Software), and a fast fourier transformation was performed and data integrated into two frequency bands: low frequency (LF: 0.20–0.75 Hz) and high frequency (0.75–2.00 Hz). The LF component represents both the sympathetic (SYM) and parasympathetic (PS) input, while the HF component corresponds to PS nervous system activity. The LF/HF ratio is used to assess relative SYM activity. Data were analyzed by Two Way ANOVA (sex x prenatal treatment). There was a significant effect of sex with females having greater HF power, and a significant interaction whereby HF power increased in males and decreased in females prenatally exposed to DEX. Neither sex nor prenatal DEX had any impact on LF power; however, there was a significant sex effect and interaction when assessing LF/HF. DEX decreased the ratio in males, but tended to increase it in females exposed to DEX, in utero. Losartan treatment in DEX exposed females significantly increased HF to a level that was not different from vehicle rats. The increased HF power in females suggests a greater reliance on PS drive than males. However, prenatal DEX exposure produces sex‐specific reductions PS drive in females, that is reversible by losartan treatment. This decrease in PS activity may underlie the altered pressor and tachycardic stress responses that we have previously observed in these rats. Additionally, these findings suggest that autonomic dysregulation following prenatal DEX may be mediated in part due to long‐term changes in central renin‐angiotensin signaling. Further studies will...