The Role of β-Defensin 1 Against Porphyromonas gingivalis Lipopolysaccharide-Mediated Inflammation in the THP-1 Cell Line

Introduction Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) is one of the crucial virulence factors of periodontitis. Antimicrobial peptides (AMPs) are emerging as alternatives or adjuncts to antibiotics in the treatment of microbial infections. In this study, cytotoxicity, anti-inflammatory activity, anti-oxidative stress, cell cycle analysis, and apoptosis properties of AMP, β-defensin 1, were studied in Pg-LPS-stimulated THP-1 (Tohoku Hospital Pediatrics - 1) cell line. Methods The cytotoxic nature of Pg-LPS and β-defensin 1 was studied by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method. The cytotoxic effect of β-defensin 1 on Pg-LPS-stimulated THP-1 cells was also studied by the same method. The anti-inflammatory role of β-defensin 1 against cyclooxygenase (COX), lipoxygenase (LOX), myeloperoxidase (MPO), and inducible nitric oxide synthase activities were studied. The anti-oxidative nature of β-defensin 1 was analyzed by measuring reactive oxygen species (ROS) generation by dichlorodihydrofluorescein diacetate (DCFDA) assay. Cell cycle distribution and apoptosis were studied by flow cytometry. The hemolytic nature of β-defensin 1 was predicted using the HemoPred web tool. Results The results of the study demonstrated that Pg-LPS showed dose-dependent cytotoxicity to THP-1 cells. β-Defensin 1 had dose-dependent cytotoxicity to THP-1 cells and showed a protective effect on THP-cells up to 1 µg/mL of Pg-LPS, beyond which cell viability decreased. β-Defensin 1 inhibited COX, LOX, MPO, and inducible nitric oxide synthase activities in a concentration-dependent manner. β-Defensin 1 showed anti-oxidative activity by suppressing the generation of ROS measured through fluorescence intensity. From the cell cycle analysis, it was found that β-defensin 1 was able to reduce the Pg-LPS-induced cell cycle arrest at the G0/G1 phase. From the apoptosis profile, β-defensin 1 was found to increase the live cells when compared to THP-1 cells stimulated only with Pg-LPS, indicating that β-defensin 1 provided a protective role to THP-1 cells. β-Defensin 1 was found to be hemolytic in nature by the HemoPred web tool. Conclusion β-Defensin 1 exerted multifunctional activities and can be considered a promising agent for controlling periodontitis.