High inflammation and mild demyelination in the peripheral nervous system induced by an intraneural injection of RR interleukin-4

Interleukin-4 as a neuromodulatory cytokine: roles and signaling in the nervous system

Although interleukin (IL)-4 is described as a prototypical anti-inflammatory cytokine, in recent years its role as a neuromodulatory cytokine has been extensively discussed. This review highlights the pivotal contributions of IL-4 during the development and normal physiology of neural cells as well as IL-4 connections with the pathophysiology of degenerative or inflammatory processes observed in the central and peripheral nervous system.

Double-stranded RNA induces iNOS gene expression in Schwann cells, sensory neuronal death, and peripheral nerve demyelination

Inflammation in the peripheral nervous system (PNS) is one of the characteristics of virus-induced peripheral neuropathy. In this inflammatory response, Schwann cells are actively involved. Previously, toll-like receptor 3 (TLR3) was reported as a receptor for double-stranded RNA (dsRNA) that induces antiviral and inflammatory responses in cells of the innate immune system. In this study, we investigated the expression and putative role of TLR3 in Schwann cells. TLR3 was constitutively expressed in Schwann cells. Stimulation with polyinosinic-polycytidylic acid, a synthetic dsRNA analogue, induced the expression of inducible nitric oxide synthase (iNOS) gene in Schwann cells. Studies on the intracellular signal transduction pathways using iSC, an immortalized Schwann cell line, revealed that dsRNA induces the activation of NF-kappaB, p38, and c-Jun N-terminal kinase (JNK). The activation of NF-kappaB, p38, JNK, and dsRNA-dependent protein kinase is required for dsRNA-mediated iNOS gene expression. However, the activation of PI3 kinase and GSK-3beta inhibited iNOS gene induction, a process mediated by their inhibitory effects on NF-kappaB and p38 activation. dsRNA-induced NO production caused neuronal cell death in cultured dorsal root ganglion. Finally, the introduction of dsRNA into the rat sciatic nerve induced iNOS gene expression and peripheral nerve demyelination in vivo. Taken together, these data suggest that viral RNA may induce inflammatory Schwann cell activation via TLR3 and peripheral nerve damage in the PNS.

IL-4 in vitro production is upregulated in Alzheimer's disease patients treated with acetylcholinesterase inhibitors

Cytokines appear to be involved in the pathogenesis of Alzheimer's Disease (AD). Their modulation by treatment has been investigated only in a few studies. The aim of our study was to evaluate the effect of acetylcholinesterase inhibitors (AChEI) on Interleukin-4 (IL-4) production in AD patients. IL-4 levels were measured by ELISA on peripheral blood mononuclear cell cultures in the presence or absence of Concanavalin A or Phytohaemagglutinin. Linear regression analysis shows that patients who have been treated, have higher levels of IL-4 independently from age, gender and comorbidity. The increased production of IL-4 in AChEI treated patients might represent an additional mechanism through which AChEI act on AD progression.