Caveolin-1 Provides Palliation for Adverse Hepatic Reactions in Hypercholesterolemic Rabbits

Abstract

Caveolins are an essential component of cholesterol-rich invaginations of the plasma membrane known as caveolae. These flask-shaped, invaginated structures participate in a number of important cellular processes, including vesicular transport, cholesterol homeostasis, and signal transduction. We investigated the effects of CAV-1 on mitochondrial biogenesis and antioxidant enzymes in hypercholesterolemia-affected target organs. A total of eighteen male New Zealand white rabbits were divided into three groups: a normal-diet group, an untreated hypercholesterolemia-induced group, and a hypercholesterolemia-induced group that received intravenous administration of antennapedia-CAV-1 (AP-CAV-1) peptide every 2 days for 2 weeks. Serum biochemistry, CAV-1 distribution, neutral lipid distribution, mitochondrial morphology, biogenesis-mediated protein content, oxidative stress balance, antioxidant enzyme levels, and apoptotic cell death of liver tissue were analysed. Hepatic and circulating cholesterol and low-density lipoprotein cholesterol (LDL-C) levels differed significantly between the three groups (P<0.05). Immunohistochemical staining intensity of CAV-1 was greater in AP-CAV-1-treated rabbits than in untreated rabbits, especially in the vicinity of the liver vasculature. The high levels of neutral lipids, malondialdehyde, peroxisome proliferator-activated receptor-γ coactive 1α (PGC-1α), and nuclear respiratory factor-1 (NRF-1) seen in untreated hypercholesteremic animals were attenuated by administration of AP-CAV-1 (P<0.05). In addition, mitochondria in animals that received treatment exhibited darker electron-dense matrix and integrated cristae. Furthermore, the levels of ROS modulator 1 (Romo1) and superoxide dismutase (SOD)-2, as well as catalase activity were significantly lower in CAV-1-treated hypercholesterolemic rabbits (P<0.05). AP-CAV-1 treatment also restored mitochondrial respiratory chain subunit protein content (OXPHOS complexes I–V), thereby preserving mitochondrial function (P<0.05). Furthermore, AP-CAV-1 treatment significantly suppressed apoptotic cell death, as evidenced by a reduction in the number of TUNEL-positive cells. Our results indirectly indicate that CAV-1 mediates the negative effects of PGC-1α on hepatic mitochondrial respiratory chain function, promotes the antioxidant enzyme defence system, and maintains mitochondrial biogenesis.