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To explore the involved mechanisms and possible treatments of ambient PM2.5 exposure-induced lung inflammation, this work studied the activity of luteolin, a natural flavonoid which widely presents in many plant species, in murine alveolar macrophage MH S cells exposed to PM2.5. Results showed PM2.5 induced an inflammatory response, as evidenced by significantly increased TNF-α, IL-6, MCP-1 and Rantes levels. and induced iNOS, COX-2, and NF-κB protein expressions in MH-S cells. Moreover, luteolin pre-treatment reduced JAK2 and STAT1 but not STAT3 protein expressions in PM2.5-stimulated MH-S cells. Performing JAK2 inhibitor AG490 further showed reduced TNF-α and IL-6 productions as well as iNOS, COX-2, and NF-κB protein expressions. In addition, although PM2.5 exposure could elevate HO-1 expression basically, luteolin pre-treatment and AG490 administration further significantly enhanced HO-1 expression additionally. Collectively, these results revealed that luteolin inhibits inflammation through suppressing JAK2/STAT1/NF-κB pathway and enhancing HO-1 expression in PM2.5-challenged alveolar macrophage MH-S cells. [ABSTRACT FROM AUTHOR]

Despite its possible therapeutic potential against COVID-19, the exact mechanism(s) by which palmitoylethanolamide (PEA) exerts its beneficial activity is still unclear. PEA has demonstrated analgesic, anti-allergic, and anti-inflammatory activities. Most of the anti-inflammatory properties of PEA arise from its ability to antagonize nuclear factor-κB (NF-κB) signalling pathway via the selective activation of the PPARα receptors. Acting at this site, PEA can downstream several genes involved in the inflammatory response, including cytokines (TNF-α, Il-1β) and other signal mediators, such as inducible nitric oxide synthase (iNOS) and COX2. To shed light on this, we tested the anti-inflammatory and immunomodulatory activity of ultramicronized(um)-PEA, both alone and in the presence of specific peroxisome proliferator-activated receptor alpha (PPAR-α) antagonist MK886, in primary cultures of murine alveolar macrophages exposed to SARS-CoV-2 spike glycoprotein (SP). SP challenge caused a significant concentration-dependent increase in proinflammatory markers (TLR4, p-p38 MAPK, NF-κB) paralleled to a marked upregulation of inflammasome-dependent inflammatory pathways (NLRP3, Caspase-1) with IL-6, IL-1β, TNF-α over-release, compared to vehicle group. We also observed a significant concentration-dependent increase in angiotensin-converting enzyme-2 (ACE-2) following SP challenge. um-PEA concentration-dependently reduced all the analyzed proinflammatory markers fostering a parallel downregulation of ACE-2. Our data show for the first time that um-PEA, via PPAR-α, markedly inhibits the SP induced NLRP3 signalling pathway outlining a novel mechanism of action of this lipid against COVID-19. [ABSTRACT FROM AUTHOR]

Acute lung injury caused by sepsis remains one of the most difficult challenges faced by patients in intensive care units and is associated with a high mortality rate. The aim of the present study was to investigate whether programmed cell death (PD)-1/programmed cell death-ligand 1 (PD-L1) inhibitors reduce alveolar macrophage apoptosis, reduce inflammatory factor release and relieve inflammation. For this purpose, murine alveolar macrophages, MH-S, were cultured and divided into control, lipopolysaccharide (LPS) and LPS+BMS-1 (PD-1/PD-L1 inhibitors) groups. LPS (10 ng/ml) was added to the LPS and LPS+BMS-1 groups for 24 h and PD-1/PD-L1 inhibitor BMS-1 (1 µmol/l) was added to the LPS+BMS-1 group for 72 h. PD-1 mRNA expression was detected using reverse transcription-quantitative PCR and PD-1 protein expression was detected using western blotting in the control, LPS and LPS+BMS-1 groups of macrophages. MH-S apoptosis was detected using flow cytometry with Annexin V/PI staining. The levels of the inflammatory factors interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and IL-10 were detected by ELISA. Murine alveolar macrophages expressed PD-1 at both the molecular and protein levels and PD-1 expression was increased in MH-S cells stimulated with LPS. Compared with the LPS group, the expression of PD-1 in the LPS+BMS-1 group was significantly decreased. Flow cytometry demonstrated that there was increased apoptosis of alveolar macrophages in the LPS group compared with the control group, whereas, alveolar macrophages notably decreased apoptosis in the LPS+BMS-1 group compared with the LPS group. There was no statistical difference between the control group and the LPS+BMS-1 group. IL-1β, IL-6, TNF-α and IL-10 were increased in the LPS group compared with the control group. The levels of IL-1β, IL-6 and TNF-α in the LPS+BMS-1 group were lower compared with those in the LPS group whereas IL-10 was further increased. In vitro, the PD-1/PD-L1 inhibitor, BMS-1, decreases alveolar macrophage apoptosis compared with the LPS group to maintain effective immune clearance and reduce inflammatory factor release. This decreased the inflammatory response and reduced acute lung injury caused by sepsis. Therefore, PD-1/PD-L1 inhibitors may be a potential therapeutic target for acute lung injury in patients with sepsis. [ABSTRACT FROM AUTHOR]