Inhibition of cyclooxygenase-2 reduces hypothalamic excitation in rats with adriamycin-induced heart failure

Abstract

Background: The paraventricular nucleus (PVN) of the hypothalamus plays an important role in the progression of heart failure (HF). We investigated whether cyclooxygenase-2 (COX-2) inhibition in the PVN attenuates the activities of sympathetic nervous system (SNS) and renin-angiotensin system (RAS) in rats with adriamycin-induced heart failure.

Methodology/principal finding: Heart failure was induced by intraperitoneal injection of adriamycin over a period of 2 weeks (cumulative dose of 15 mg/kg). On day 19, rats received intragastric administration daily with either COX-2 inhibitor celecoxib (CLB) or normal saline. Treatment with CLB reduced mortality and attenuated both myocardial atrophy and pulmonary congestion in HF rats. Compared with the HF rats, ventricle to body weight (VW/BW) and lung to body weight (LW/BW) ratios, heart rate (HR), left ventricular end-diastolic pressure (LVEDP), left ventricular peak systolic pressure (LVPSP) and maximum rate of change in left ventricular pressure (LV±dp/dtmax) were improved in HF+CLB rats. Angiotensin II (ANG II), norepinephrine (NE), COX-2 and glutamate (Glu) in the PVN were increased in HF rats. HF rats had higher levels of ANG II and NE in plasma, higher level of ANG II in myocardium, and lower levels of ANP in plasma and myocardium. Treatment with CLB attenuated these HF-induced changes. HF rats had more COX-2-positive neurons and more corticotropin releasing hormone (CRH) positive neurons in the PVN than did control rats. Treatment with CLB decreased COX-2-positive neurons and CRH positive neurons in the PVN of HF rats.

Conclusions: These results suggest that PVN COX-2 may be an intermediary step for PVN neuronal activation and excitatory neurotransmitter release, which further contributes to sympathoexcitation and RAS activation in adriamycin-induced heart failure. Treatment with COX-2 inhibitor attenuates sympathoexcitation and RAS activation in adriamycin-induced heart failure.

Figure 1. Effect of CLB on anatomical indicators of heart failure.

A. Representative microphotogaph of myocardium in different groups. B. Representative microphotogaph of Lung in different groups. C. Group data showing the effect of treatment with celecoxib (CLB) via intragastric administration on VW/BW (ratio of ventricle to body weight) and LW/BW (ratio of lung to body weight) in ADM-induced heart failure (HF) rats. *P<0.01 vs. control group; ^# P<0.01 vs. HF group.

Figure 2. Effect of CLB on plasma levels of ANG II, NE and ANP in ADM-induced HF rats.

A. Plasma ANG II. B. Plasma NE. C. Plasma ANP. HF rats had the higher plasma levels of ANG II and NE when compared with control rats, which were obviously lower in HF+CLB rats. Plasma ANP was lower in HF rats than in control rats. Plasma ANP in HF+CLB rats was significantly higher than in HF rats. *P<0.01 vs. control group; ^# P<0.01 vs. HF group.

Figure 3. Effect of CLB on myocardial levels of ANG II and ANP in ADM-induced HF rats.

A. Comparison of myocardial AngII. Myocardial ANG II level was higher in HF rats than in control rats. The myocardial ANG II level was significantly lower in HF+CLB rats than in HF rats. B. Comparison of myocardial ANP. The myocardial ANP level was lower in HF rats than in control rats. The HF+CLB rats had significantly higher ANP level than the HF model rats.*P<0.01 vs. control group; ^# P<0.01, ^## P<0.05 vs. HF group.

Figure 4. Effect of CLB on PVN levels of ANG II and NE in HF rats.

A. Comparison of ANG II level. B. Comparison of NE level. The PVN levels of ANG II and NE were higher in HF rats than in control rats. The PVN levels of ANG II and NE were lower in HF+CLB rats than in HF rats. *P<0.01 vs. control group; ^# P<0.01 vs. HF group.

Figure 5. Comparison of protein expression for COX-2 in the PVN in rats.

Representative Western blots were aligned with the matching grouped relative optical density values of immunoblot band. COX-2 protein expression in the PVN increased in HF rats when compared with control rats. The PVN level of COX-2 protein expression was lower in HF+CLB rats than in HF rats. *P<0.01 vs. control group; ^## P<0.05 vs. HF group.

Figure 6. CRH and COX-2 expression in the PVN in control, HF and HF+CLB rats.

A. Immunohistochemistry for CRH (deep brown dots) and COX-2 (brown) positive neurons in control, HF and HF+CLB rats. B. Bar graph comparing numbers of PVN CRH and COX-2 positive neurons in different groups. The HF rats had more COX-2 and CRH-positive neurons in the PVN than control rats. There were fewer positive neurons of COX-2 and CRH in the PVN of HF+CLB rats than in HF rats. *P<0.01 vs. control group; ^# P<0.01 vs. HF group.

Figure 7. Glutamate and GABA release in the PVN in control, HF and HF+CLB rats.

Compared with control rats, HF rats had higher levels of glutamate in the PVN. Glutamate release in the PVN was lower in HF+CLB rats than in HF rats. However, there were no significant differences in GABA among control, HF, and HF+CLB rats. *P<0.01 vs. control group; ^# P<0.01 vs. HF group.