A Polyphenol Rich Muscadine Grape Extract Reduces Macrophage Infiltration in Hypertensive Rat Hearts Associated with a Reduction in Macrophage Migration

Abstract

Objectives

Hypertension affects over a billion people world-wide and is a major risk factor for cardiovascular disease. Macrophages, the most abundant innate immune cells, home to the heart and secrete cytokines, inducing a heightened inflammatory response which results in fibrosis and cardiac damage. Muscadine grapes are rich in polyphenols, compounds with anti-proliferative, anti-fibrotic, and anti-inflammatory properties. Our aim was to determine whether a muscadine grape extract (MGE) rich in polyphenols prevents the macrophage inflammatory response induced by hypertension.

Methods

A proprietary extract was prepared from muscadine grape seeds and skins. Male Sprague-Dawley rats (8 weeks old) received drinking water (control), MGE at 0.2 mg total phenolics/mL, 24 μg/kg/h of angiotensin II (Ang II) via osmotic minipump to induce hypertension, or both Ang II and MGE (Ang II/MGE) for 4 weeks. Rats were pre-treated with MGE for 1 week prior to Ang II treatment. Blood pressure was measured weekly by tail cuff plethysmography. Tissues were collected and fixed for immunohistochemistry. Proliferation and migration of macrophage-like RAW264.7 cells were quantified in real-time.

Results

MGE had no effect on blood pressure in normotensive or hypertensive rats. MGE ameliorated Ang II-induced diastolic dysfunction (E/E’ ratio: 19.9 ± 0.8 control, 28.1 ± 1.1 Ang II, 22.3 ± 2.0 Ang II/MGE rats; n = 8; P < 0.05), interstitial cardiac fibrosis ( P < 0.05) and collagen III deposition (0.9 ± 0.2% Control, 6.8 ± 1.0% Ang II, 2.8 ± 0.4% Ang II/MGE; P < 0.01). Thus, MGE may improve diastolic dysfunction in part through a reduction in pathological fibrosis. Ang II caused a significant increase in CD68-positive macrophages in cardiac tissue, which was blocked by MGE (% positive cells/field: control 6.1 ± 0.4, Ang II 12.5 ± 2.0, Ang II/MGE 5.4 ± 0.5, P < 0.01). Treatment of RAW264.6 cells with MGE (20 μg/mL total phenolics) for 18 h attenuated stimulated cell migration by 2-fold with no effect on proliferation ( n = 3, P < 0.5), indicating that MGE may reduce the Ang II-mediated increase in cardiac macrophages by blocking migration.

Conclusions

MGE may serve as medical food to protect the heart from hypertension-induced inflammation thereby reducing cardiac fibrosis to improve diastolic dysfunction.

Funding Sources

Chronic Disease Research Fund.