Lupeol-induced nitric oxide elicits apoptosis-like death within Escherichia coli in a DNA fragmentation-independent manner

Abstract

Lupeol is known to be plentiful in fruits or plant barks and has an antimicrobial effect, however, its mode of action(s) has yet to be determined. To elucidate lupeol generates nitric oxide (NO), which is recognized for possessing an antimicrobial activity, intracellular NO was measured in Escherichia coli using DAF-FM. Using the properties of NO passing through plasma membrane easily, increased malondialdehyde levels have shown that lupeol causes lipid peroxidation, and the resulting membrane depolarization was confirmed by DiBAC4(3). These data indicated that lupeol-induced NO is related to destruction of bacterial membrane. Further study was performed to examine whether NO, known as a cell proliferation inhibitor, affects bacterial cell division. As a result, DAPI staining verified that lupeol promotes cell division arrest, and followed by early apoptosis is observed in Annexin V/PI double staining. Even though these apoptotic hallmarks appeared, the endonuclease failed to perform properly with supporting data of decreased intracellular Mg2+ and Ca2+ levels without DNA fragmentation, which is confirmed using a TUNEL assay. These findings indicated that lupeol-induced NO occurs DNA fragmentation-independent bacterial apoptosis-like death (ALD). Additionally, lupeol triggers DNA filamentation and morphological changes in response to DNA repair system called SOS system. In accordance with the fact that ALD deems to SOS response, and that the RecA is considered as a caspase-like protein, increase of caspase-like protein activation occurred in E. coli wild-type, and no ΔRecA mutant. In conclusion, these results demonstrated that the antibacterial mode of action(s) of lupeol is an ALD while generating NO.

Ultrasonic cavitation induced Vibrio parahaemolyticus entering an apoptosis-like death process through SOS response

“…Among them, the SOS response system of bacteria, as an emergency damage repair mechanism, is a highly conserved biological evolutionary mechanism present in the vast majority of bacteria, which repair the damaged genomes of bacteria and help them to overcome some external stresses, adapt to changes in the environment, and maintain a high survival rate [24] . However, when the damage is too severe or too long to be repaired, the activation of the SOS response system may lead to the initiation of the self-regulatory and apoptotic mechanisms of the bacteria, thus triggering the programmed death of the bacteria [16] .…”

Linolenic acid-metronidazole inhibits the growth of Helicobacter pylori through oxidation

“…Damaged DNA appears as dots. Therefore, the fragmentation of H. pylori DNA after Lla-Met treatment was detected using the DAPI staining[ 23 ]. Briefly, the G27 bacterial suspension (1 × 10 8 CFU/mL) was incubated with or without 40 mmol/L L-cys for 1 h and thereafter with Lla-Met (16 μg/mL) for 2 h. Thereafter, the suspension was centrifuged to remove the supernatant and treated with DAPI (1 μg/mL) for 30 min.…”

A Triterpenoid Lupeol as an Antioxidant and Anti-Neuroinflammatory Agent: Impacts on Oxidative Stress in Alzheimer’s Disease

“…It is available in fruits (e.g., mango, fig, strawberry, and red grapes), vegetables (e.g., white cabbage, pepper, cucumber, and tomato), and numerous other medicinal plants [13,14]. Lupeol has shown beneficial effects against numerous health issues, including anti-cancer, anti-microbial [59], anti-diabetic [60], cardio [61], and hepatoprotection [62] (Table 1).…”