Interleukin-4 Induces the Release of Opioid Peptides from M1 Macrophages in Pathological Pain

Abstract

Interleukin-4 (IL-4) is an anti-inflammatory cytokine, which can be protective in inflammatory and neurologic disorders, and can alleviate pain. Classically, IL-4 diminishes pain by blocking the production of proinflammatory cytokines. Here, we uncovered that IL-4 induces acute antinociception by IL-4 receptor a (IL-4Ra)-dependent release of opioid peptides from M1 macrophages at injured nerves. As a model of pathologic pain, we used a chronic constriction injury (CCI) of the sciatic nerve in male mice. A single application of IL-4 at the injured nerves (14 d following CCI) attenuated mechanical hypersensitivity evaluated by von Frey filaments, which was reversed by co-injected antibody to IL-4Ra, antibodies to opioid peptides such as Met-enkephalin (ENK), b-endorphin and dynorphin A 1-17, and selective antagonists of d-opioid, m-opioid, and j-opioid receptors. Injured nerves were predominately infiltrated by proinflammatory M1 macrophages and IL-4 did not change their numbers or the phenotype, assessed by flow cytometry and qRT-PCR, respectively. Macrophages isolated from damaged nerves by immunomagnetic separation (IMS) and stimulated with IL-4 dose dependently secreted all three opioid peptides measured by immunoassays. The IL-4-induced release of ENK was diminished by IL-4Ra antibody, intracellular Ca 21 chelator, and inhibitors of protein kinase A (PKA), phosphoinositide 3-kinase (PI3K), and ryanodine receptors. Together, we identified a new opioid mechanism underlying the IL-4-induced antinociception that involves PKA-mediated, PI3K-mediated, ryanodine receptor-mediated, and intracellular Ca 21 -mediated release from M1 macrophages of opioid peptides, which activate peripheral opioid receptors in injured tissue.

Amelioration of injury-induced tissue acidosis by a nonsteroidal analgesic attenuates antinociceptive effects of the pH-dependent opioid agonist NFEPP

“…5 ). Because we have previously shown that IL-4 induced the release of opioid peptides from macrophages 22 , we also attempted to examine the mRNA of IL-4, but did not detect it in immune cells from inflamed paws of either DCF- or vehicle-treated control animals (data not shown).

Figure 5 Expression of inflammatory mediator mRNAs in inflamed paw tissue.

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“…Rib bones were used as anatomical landmarks to identify L4, L5 and L6 DRG, which were then extracted using curved watchmaker forceps. The three DRG were pooled in a screw cap 1.5 ml tube, deep frozen in liquid nitrogen and stored at − 80 °C until RNA extraction 21 , 22 .…”

Burning and Scaling Probably Associated with Dupilumab Therapy: A Case Report

“…IL-4 plays a protective role in neurological disorders and can be analgesic. Pain relief is achieved in two ways: 12 , 13 (i) by blocking the production of pro-inflammatory cytokines (eg, IL-1β, tumor necrosis factor, prostaglandin E2), (ii) by applying IL-4 to damaged nerves, which can achieve analgesic effects through IL-4Rα-mediated release of opioid peptides from M1 macrophages; IL-4 can also transfer macrophages from the M1 phenotype to the M2 phenotype, resulting in the production of opioid peptides in damaged nerves for pain relief. IL-13 is a pleiotropic cytokine that can be produced by a variety of cells and is particularly well known in the field of allergy and asthma.…”

Macrophage as a Peripheral Pain Regulator

“…Activation of PLC, PKC or cyclic AMP/PKA signals enhances the activity of transient receptor potential vanilloid 1 (TRPV1), TRPA1 or Ca v 3.2 channels, known as pro-nociceptive cation channels, contributing to pathological pain [66][67][68][69] (Figure 2B). On the other hand, M2 macrophages secrete IL-10, which in turn suppresses neuronal excitability and neuropathic pain (Figure 2B), and there is also evidence for anti-nociceptive roles of macrophage-derived opioid peptides [70,71].…”