Imunosuppresive Activity of Momordica charantia L. fruit extract on the NF-κB pathway in Drosophila melanogaster

Abstract

The activation of the NF-kB pathway leading to the production of proinflammatory cytokines is a critical feature in innate antiviral immunity. However, in SARS-CoV-2 infection, a high number of cases with a prolonged late-stage stimulation of cytokine production that leads to a cytokine storm phenotype, an undesirable, dangerous immune-related state that can cause multiple organ failures, have been reported. To treat this, immunosuppressants with selective action on the innate NF-kB pathway are urgently required. Bitter gourd (Momordica charantia L.) has been reported to yield anti-inflammatory activity, thus might be a potential candidate for such effort. In this study, we carried out experimental procedures on the PGRP-LB mutant line of Drosophila melanogaster to examine the immunosuppressive effect of Momordica charantia L. fruit extract (MCFE) on the NF-kB pathway. Initial phytochemical screening revealed that Momordica charantia L. fruit extract contains alkaloids, flavonoids, tannins, and saponins. Furthermore, the phenotypical analysis demonstrated that MCFE could improve the survival and locomotor of the PGRP-LB mutant line of Drosophila melanogaster in a concentration-dependent manner. Additional gene expression analysis revealed that the expression of dpt and dro, two important downstream genes in the Imd (NF-kB) pathway of D. melanogaster, was significantly reduced, in a different expression profile, in response to MCFE treatment. However, it is important to note that while the expression of dpt was dramatically repressed in all extract-treated groups, the expression of dro occurred in a concentration-dependent manner. These results strongly support the notion that Momordica charantia L. can reduce the expression of proinflammatory cytokines downstream of the NF-kB pathway, hence potential to be used as a source candidate to harvest prospective immunosuppressive compounds to alleviate the cytokine storm condition.

Curcumin-mediated gene expression changes in Drosophila melanogaster

“…Autoinflammatory phenotypes can be observed in an experimental model organism, including the PGRP-LB Δ D. melanogaster. Previously, the authors' group showed that the PGRP-LB Δ flies have shorter lifespans than their Oregon R wildtype counterparts (Asfa et al, 2022;Nainu et al, 2022). This is probably due to the loss of the PGRP-LB protein which functions as a negative regulator of the Imd pathway in D. melanogaster (Orlans et al, 2021).…”

“…This is probably due to the loss of the PGRP-LB protein that plays an important function in the homeostatic regulation of the NF-kB pathway, Relish, in D. melanogaster. In the absence of this PGRP-LB protein, overexpression of immune-related genes, under the Imd (NF-κB) pathway was observed (Kounatidis et al, 2017;Asfa et al, 2022;Nainu et al, 2022). Based on the observation of the survival assay, the PGRP-LB Δ flies in the untreated control group succumbed up to 100% on day 30, while on the same day, there were still live PGRP-LB Δ in the curcumin-treated groups at all concentrations.…”

“…In this study, the authors used two-four days old adult Peptidoglycan recognition protein LB (PGRP-LB Δ ) D. melanogaster. This is a mutant line lacking the expression of PGRP-LB, that has been shown to experience overactivation of the NF-κB immune deficiency (Imd) pathway in D. melanogaster (Asfa et al, 2022), upon the introduction of a proper ligand. Flies were constantly maintained in the fly culture vials under standard laboratory conditions (25°C, 12 hours light and 12 hours dark cycles, and normal cornmealbased fly food).…”

Drosophila as an Animal Model for Testing Plant-Based Immunomodulators

“…The lack of PGRP-LB has been demonstrated to stimulate overactivation of the NF-κB (IMD) pathway in flies. They found that the extract enhanced the survival and locomotion of PGRP-LB mutants in a concentration-dependent manner and reduced the expression of Dpt and Dro , the downstream genes in the IMD pathway [ 59 ].…”