Search

Background and Purpose: The Janus Kinase (JAK) family mediates the cytokine receptor-induced signalling pathways involved in inflammatory processes. The activation of the signal transducers and activators of transcription (STATs) by JAK kinases is a key point in these pathways. Four JAK proteins, JAK1, JAK2, JAK3 and tyrosine kinase 2 (Tyk2) associate with the intracellular domains of surface cytokine receptors are phosphorylating STATs and modulating gene expression. The aim of this study was to explore the role of JAK inhibition in an acute model of inhaled lipopolysaccharide (LPS)-induced airway inflammation in rats through evaluating the effects of tofacitinib, a marketed pan-JAK inhibitor. Specifically, some pulmonary inflammation parameters were studied and the lung STAT3 phosphorylation was assessed as a target engagement marker of JAK inhibition in the model., Experimental Approach: Rats were exposed to an aerosol of LPS (0.1 mg/ml) or phosphate-buffered saline (PBS) during 40 min. Bronchoalveolar lavage fluid (BALF) and lung samples were collected 4 h after PBS or LPS exposure. Neutrophils in BALF were counted and a panel of cytokines were measured in BALF. Phosphorylation of STAT3 was studied in lung homogenates by ELISA and localization of phospho-STAT3 (pSTAT3) in lung tissue was also evaluated by immunohistochemistry. In order to assess the effect of JAK inhibition, tofacitinib was administered 1 h before challenge at doses of 3, 10 and 30 mg/kg p.o., Key Results: Inhaled LPS challenge induced an augment of neutrophils and cytokines in the BALF as well as an increase in pSTAT3 expression in the lungs. Tofacitinib by oral route inhibited the LPS-induced airway neutrophilia, the levels of some cytokines in the BALF and the phosphorylation of STAT3 in the lung tissue., Conclusions and Implications: In summary, this study shows that JAK inhibition ameliorates inhaled LPS-induced airway inflammation in rats, suggesting that at least JAK/STAT3 signalling is involved in the establishment of the pulmonary neutrophilia induced by LPS. JAKs inhibitors should be further investigated as a potential therapy for respiratory inflammatory diseases., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Since the discovery of the first matrix metalloproteinase (MMP), this ever-growing family of proteinases has been the subject of intense research. Although it was initially believed that MMPs were solely involved in matrix turnover and degradation, there are now data suggesting MMPs are actively involved in the inflammatory process. In previous studies, we have demonstrated an increase in MMP expression in human cell-based assays and in preclinical rat models of airway inflammation. Therefore, the aim of this study was to characterize the role of MMPs in these models by profiling the impact of a broad-spectrum MMP inhibitor. In lipopolysaccharide (LPS)-stimulated THP-1 cells and primary human lung tissue macrophages, the MMP inhibitor had no significant effect on the release of tumor necrosis factor-alpha, interleukin (IL)-8, IL-1 beta, growth-regulated oncogene-alpha, macrophage inflammatory protein-1 alpha, or IL-6 whereas dexamethasone has a significant impact on all cytokines from both cell types. Similarly, in the more biologically complex LPS-driven rat model of airway inflammation, the MMP inhibitor did not have an impact on mediator release and cellular burden. The compound did, however, significantly reduce levels of lung MMP-9. Furthermore, in a "disease" model, the compound did not affect cellular inflammation but did significantly reduce elastase-induced experimental emphysema. In summary, these data demonstrate for the first time that MMPs do not play a role in the increase in inflammatory mediators or cellular burden observed in these preclinical models. However, they do appear to be involved in the elastase-driven breakdown of airway structure, which is not due to a direct effect of the stimulus.

Nitric oxide (NO), synthesised by different isoforms of nitric oxide synthase (NOS), has been linked with the development and maintenance of nociception. We studied the role of the inducible isoform, iNOS, in two different rat pain models with an inflammatory component. iNOS was immunohistochemically detected locally in the paw 6h after Freund's Complete Adjuvant (FCA) injection, showing a plateau at 24-72 h and falling slowly in the following weeks. This correlated with the late phase of the hypersensitivity to pain revealed in the behavioural tests. A highly selective iNOS inhibitor GW274150 (1-30 mg/kg orally, 24h after FCA) suppressed the accumulation of nitrite in the inflamed paw indicating substantial iNOS inhibition. At the same time it partially reversed FCA-induced hypersensitivity to pain and edema in a dose-dependent manner. After Chronic Constriction Injury (CCI) surgery to the sciatic nerve, iNOS presence was only detected locally in the region of the nerve (inflammatory cells). GW274150 (3-30 mg/kg orally, 21 days after surgery) also reversed significantly the CCI-associated hypersensitivity to pain. No iNOS was detectable in dorsal root ganglia, spinal cord or brain in either model. This study demonstrates a role for peripherally-expressed iNOS in pain conditions with an inflammatory component and the potential value of iNOS inhibitors in such conditions.

Abstract: Clinically, inflammatory pain is far more persistent than that typically modelled pre-clinically, with the majority of animal models focussing on short-term effects of the inflammatory pain response. The large attrition rate of compounds in the clinic which show pre-clinical efficacy suggests the need for novel models of, or approaches to, chronic inflammatory pain if novel mechanisms are to make it to the market. A model in which a more chronic inflammatory hypersensitivity phenotype is profiled may allow for a more clinically predictive tool. The aims of these studies were to characterise and validate a chronic model of inflammatory pain. We have shown that injection of a large volume of adjuvant to the intra-articular space of the rat knee results in a prolonged inflammatory pain response, compared to the response in an acute adjuvant model. Additionally, this model also results in a hypersensitive state in the presence and absence of inflammation. A range of clinically effective analgesics demonstrate activity in this chronic model, including morphine (3mg/kg, t.i.d.), dexamethasone (1mg/kg, b.i.d.), ibuprofen (30mg/kg, t.i.d.), etoricoxib (5mg/kg, b.i.d.) and rofecoxib (0.3–10mg/kg, b.i.d.). A further aim was to exemplify the utility of this chronic model over the more acute intra-plantar adjuvant model using two novel therapeutic approaches; NR2B selective NMDA receptor antagonism and iNOS inhibition. Our data shows that different effects were observed with these therapies when comparing the acute model with the model of chronic inflammatory joint pain. These data suggest that the chronic model may be more relevant to identifying mechanisms for the treatment of chronic inflammatory pain states in the clinic. [Copyright &y& Elsevier]

An abstract of the article "Poly I:C causes exacerbation in a murine allergic inflammation model driven by house dust mite in Freund's complete adjuvant," by Jorge De Alba and colleagues is presented.