Pharmacological investigation of Nox2-NADPH oxidase inhibitors and p47phox redox-signalling in angiotensin II-induced cardiac hypertrophy in mice

Reactive oxygen species (ROS) are involved in the signal transduction and cell defence in mammalian cells. However, excessive ROS derived under pathophysiological conditions are associated with the development of a wide range of diseases including cardiovascular, metabolic, neurodegenerative diseases and cancer. gp91phox-containing NADPH oxidase (Nox2) was found to be one of the primary enzymatic sources of ROS and p47phox is its key regulator. LMH001 was developed in this lab as an inhibitor of Nox2 targeting p47phox , but its chemical properties and preclinical pharmacokinetics and pharmacodynamics (PK/PD) have not been studied. At the same time, the role of p47phox and its signalling pathways under pathophysiological conditions remained unclear. Therefore, the overall aim of this study is to characterise the PK/PD properties of LMH001 and understand its mechanism in depth by knockout (KO) of p47phox in Angiotensin II (AngII)-induced oxidative stress and cardiac hypertrophy model. The plasma concentration of LMH001 showed a mono-exponential decline pattern with a t1/2 = 0.042 h and a clearance = 5682.63 mL/h/kg, and its effect in reducing AngII-stimulated H9C2 (a rat myoblast cell line) ROS production showed an IC50 = 124.00 ± 42.6 ng/ml. In the AngII-induced hypertrophic models, wild type (WT) mice displayed significantly raised systolic blood pressure (SBP) and induced cardiac hypertrophy after AngII-infusion. In contrast, p47phox KO mice only demonstrated a mild increase in SBP without hypertrophy. There was also phosphorylation of ERK1/2, p38 MAPK and MAPK kinase 3/6 (MKK3/6). Apoptosis was suggested by increased levels of H2AX and apoptosis signal-regulating kinase 1 (ASK1) phosphorylation. In conclusion, p47phox plays a crucial role in AngII-induced cardiac oxidative stress and hypertrophy. Its signalling through MKK3/6, p38MAPK and ERK1/2 phosphorylation are essential in H2AX and ASK1 phosphorylation and cardiomyocyte apoptosis. This study also provided vital information on the chemical properties, PK/PD, and pharmacological efficacy of LMH001. Its potential as a drug candidate for oxidative stress-related diseases was discussed, and future experiments on the development of LMH drugs were suggested.