Luteolin-rich fraction from Perilla frutescens seed meal inhibits spike glycoprotein S1 of SARS-CoV-2-induced NLRP3 inflammasome lung cell inflammation via regulation of JAK1/STAT3 pathway: A potential anti-inflammatory compound against inflammation-induced long-COVID

Abstract

ObjectiveThe multi-systemic inflammation as a result of COVID-19 can persevere long after the initial symptoms of the illness have subsided. These effects are referred to as Long-COVID. Our research focused on the contribution of the Spike protein S1 subunit of SARS-CoV-2 (Spike S1) on the lung inflammation mediated by NLRP3 inflammasome machinery and the cytokine releases, interleukin 6 (IL-6), IL-1beta, and IL-18, in lung epithelial cells. This study has attempted to identify the naturally- occurring agents that act against inflammation-related long-COVID. The seed meal of Perilla frutescens (P. frutescens), which contains two major dietary polyphenols (rosmarinic acid and luteolin), has been reported to exhibit anti-inflammation activities. Therefore, we have established the ethyl acetate fraction of P. frutescens seed meal (PFEA) and determined its anti-inflammatory effects on Spike S1 exposure in A549 lung cells.MethodsPFEA was established using solvent-partitioned extraction. Rosmarinic acid (Ra) and luteolin (Lu) in PFEA were identified using the HPLC technique. The inhibitory effects of PFEA and its active compounds against Spike S1-induced inflammatory response in A549 cells were determined by RT-PCR and ELISA. The mechanistic study of anti-inflammatory properties of PFEA and Lu were determined using western blot technique.ResultsPFEA was found to contain Ra (388.70 ± 11.12 mg/g extract) and Lu (248.82 ± 12.34 mg/g extract) as its major polyphenols. Accordingly, A549 lung cells were pre-treated with PFEA (12.5-100 μg/mL) and its two major compounds (2.5-20 μg/mL) prior to the Spike S1 exposure at 100 ng/mL. PFEA dose-dependently exhibited anti-inflammatory properties upon Spike S1-exposed A549 cells through IL-6, IL-1β, IL-18, and NLRP3 gene suppressions, as well as IL-6, IL-1β, and IL-18 cytokine releases with statistical significance (p < 0.05). Importantly, Lu possesses superior anti-inflammatory properties when compared with Ra (p < 0.01). Mechanistically, PFEA and Lu effectively attenuated a Spike S1-induced inflammatory response through downregulation of the JAK1/STAT3-inflammasome-dependent inflammatory pathway as evidenced by the downregulation of NLRP3, ASC, and cleaved-caspase-1 of the NLRP3 inflammasome components and by modulating the phosphorylation of JAK1 and STAT3 proteins (p < 0.05).ConclusionThe findings suggested that luteolin and PFEA can modulate the signaling cascades that regulate Spike S1-induced lung inflammation during the incidence of Long-COVID. Consequently, luteolin and P. frutescens may be introduced as potential candidates in the preventive therapeutic strategy for inflammation-related post-acute sequelae of COVID-19.

Inflammasomes: a rising star on the horizon of COVID-19 pathophysiology

“…These findings provided evidence for the potential application of hesperetin in the prevention of SARS-CoV-2-induced chronic inflammation. The ethyl acetate fraction of Perilla frutescens (PFEA) and luteolin were found to quench SARS-CoV-2 S1induced NLRP3 inflammasome activation in lung cells via downregulation of the Janus kinase 1 (JAK1)/signal transducer and activator of transcription 3 (STAT3) signaling, as shown by decreased expression of NLRP3, ASC and caspase-1 (97). PFEA and luteolin could be introduced as preventive agents against inflammation-associated post-acute sequelae in COVID-19 patients.…”

Luteolin inhibits spike protein of severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) binding to angiotensin‐converting enzyme 2

“…Several studies have reported the potential benefits of luteolin for COVID-19 patients, including improvement of smell disorders (De Luca et al, 2022;Di Stadio et al, 2022, reduction of lung inflammation (Demopoulos et al, 2020;Dissook et al, 2023;Feng et al, 2022;Peter et al, 2021;Theoharides, 2020;Theoharides & Conti, 2021), and alleviation of brain fog (Kempuraj et al, 2021;Theoharides, 2022;. Moreover, luteolin has been found to directly inhibit SARS-CoV-2 infection.…”

“…Luteolin, 3′,4′,5,7‐tetrahydroxyflavone, is a common flavonoid that exists in many plants including fruits, vegetables, and medicinal herbs, and has immune‐regulation, anti‐inflammation, antioxidant, anticancer, and antiviral activities (Aziz et al, 2018; Jiang et al, 2021; Li et al, 2019). Several studies have reported the potential benefits of luteolin for COVID‐19 patients, including improvement of smell disorders (De Luca et al, 2022; Di Stadio et al, 2022, 2023), reduction of lung inflammation (Demopoulos et al, 2020; Dissook et al, 2023; Feng et al, 2022; Peter et al, 2021; Theoharides, 2020; Theoharides & Conti, 2021), and alleviation of brain fog (Kempuraj et al, 2021; Theoharides, 2022; Theoharides et al, 2021). Moreover, luteolin has been found to directly inhibit SARS‐CoV‐2 infection.…”

Increased galanin-galanin receptor 1 signaling, inflammation, and insulin resistance are associated with affective symptoms and chronic fatigue syndrome due to Long COVID

“…As mentioned in the Introduction, recent findings suggest that Long COVID is characterized by heightened immune-inflammatory pathways and oxidative stress. This is supported by the presence of increased CRP, the NLRP3 inflammasome, elevated lipid peroxidation, and reduced antioxidant defenses 12,[55][56][57] . The current research indicates that individuals with Long COVID exhibit elevated levels of serum PGE2 and CRP compared to the control group, providing additional evidence of the involvement of immune-inflammatory mechanisms.…”