Meloxicam treatment disrupts the regional structure of innate inflammation sites by targeting the pro‐inflammatory effects of prostanoids

Abstract

Background and PurposeNon‐steroidal anti‐inflammatory drugs (NSAIDs) are the most widely prescribed drugs in the world due to their analgesic, antipyretic and anti‐inflammatory effects. However, NSAIDS inhibit prostanoid synthesis, interfering with their pro‐inflammatory and anti‐inflammatory functions, and potentially prolonging acute inflammation.Experimental ApproachWe used high‐content immunohistochemistry to define the impact of meloxicam treatment on spatially separated pro‐ and anti‐inflammatory processes during innate inflammation in mice induced by zymosan. This allowed us to determine the effect of meloxicam treatment on the organization of pro‐ and anti‐inflammatory microenvironments thereby identifying relevant changes in immune cell localization, recruitment and activation.Key ResultsMeloxicam treatment reduced zymosan‐induced thermal hypersensitivity at early time points but delayed its resolution. High‐content immunohistochemistry revealed that the pro‐inflammatory area was smaller after treatment, diminishing neutrophil recruitment, M1‐like macrophage polarization, and especially phagocytosis by neutrophils and macrophages. The polarization of macrophages toward the M2‐like anti‐inflammatory phenotype was unaffected and the number of anti‐inflammatory eosinophils actually increased.Conclusion and ImplicationsHigh‐content immunohistochemistry was able to identify relevant meloxicam‐mediated effects on inflammatory processes based on alterations in the regional structure of inflammation sites. Meloxicam delayed the clearance of pathogens by inhibiting pro‐inflammatory processes, causing prolonged inflammation. Our data suggest that the prescription of NSAIDs as a treatment during an acute pathogen‐driven inflammation should be reconsidered in patients with compromised immune systems.

Mast cell-derived interleukin-4 mediates activation of dendritic cell during toll-like receptor 2-mediated inflammation

“…Distance analyses were performed with ImageJ (Fiji v.2.9.0) ( 25 ) as published previously ( 15 ). Shortly, the tissue localization of PhenoGraph clusters was visualized by histoCAT and used for the following analysis.…”

“…To determine mediator production in activated dendritic cells, cells inflamed were isolated from paw tissue as described previously ( 4 , 14 , 15 ) and where then treated over night with a 1 µg/ml solution of Brefeldin A (Sigma-Aldrich, St. Louis, USA) in RPMI 1640 medium (Gibco, Carlsbad, USA) to prevent the secretion of cytokines by inhibiting protein transport. After overnight incubation, the residual cells were collected by centrifugation at 1000 g for 5 minutes, and were then divided in two equal cell pellets.…”

“…Zymosan, a commonly used inducer of TLR2-mediated local inflammation, is arrested at its site of injection due to its a particulate structure. Injection of fluorescence-labeled zymosan can, therefore, be used to define the organization of an inflamed area relative to the pathogen ( 13 – 15 ). The localization of immune cells in regard to zymosan can then be determined using high-content immunohistochemistry technologies, such as Multi-Epitope-ligand-Carthography (MELC).…”

“…During a zymosan-induced local inflammation, the major cells of the innate immune system are the major immune cell populations in the inflamed tissue (i.e. neutrophils, eosinophils, macrophages, dendritic cells (DC), mast cells) ( 14 , 15 ). The structure of a TLR2-mediated inflammation comprises a core-region with the pathogen as well as neutrophils and M1-like macrophages.…”

“…This core region is surrounded by a pro-inflammatory (PI)-region dominated by M1-like macrophages. The PI-region is then neighbored by an anti-inflammatory (AI)-region characterized by the presence of M2-like macrophages ( 14 , 15 ). It should be noted that the AI-region may also include pro-resolution processes.…”