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.
Keywords: BALF; Inhaled LPS rat model; JAK; Lung inflammation; STAT3; Tofacitinib.
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