This study investigated the role of TRPA1 in the development and maintenance of mechanical and cold hyperalgesia in persistent inflammation induced by Complete Freund's Adjuvant (CFA) in mice. The intraplantar (i.pl.) injection of CFA induced a long lasting (28 days) hyperalgesia for both mechanical and thermal (cold) stimuli. The intraperitoneal (i.p., 30-300 mg/kg), intraplantar (i.pl., 100 microg/site) or intrathecal (i.t., 10 microg/site) injection of the TRPA1 selective antagonist HC-030031 significantly reduced the mechanical hyperalgesia evaluated by the von Frey hair test. The effect of HC-030031 was evidenced on the day after CFA injection and was kept throughout the test. However, the intracerebroventricular (i.c.v., 10 microg/site) injection of HC-030031 did not interfere with CFA-induced hyperalgesia. Treatment with HC-030031 (300 mg/kg, i.p.) completely inhibited the noxious cold hyperalgesia induced by tetrafluoroethane in mice that received CFA. The pre-treatment with the TRPA1 oligonucleotide antisense (AS-ODN, i.t.) consistently prevented both mechanical and cold hyperalgesia. Interestingly, both TRPA1 protein expression and mRNA were over-expressed in spinal cord and dorsal root ganglia (DRG) of mice treated with CFA, an effect that was fully prevented by the pre-treatment with the TRPA1 antagonist HC-030031. Collectively, the present results showed that TRPA1 present at either peripheral or spinal sites play a relevant role in the development and maintenance of both mechanical and cold hyperalgesia during CFA-induced inflammation. Thus, TRPA1 selective antagonists represent promising candidates to treat hyperalgesia in persistent inflammatory states.

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Quercetin is a plant-derived flavonoid widely known by its anti-oxidant and anti-inflammatory properties, but its oral bioavailability is very poor and this becomes difficult to assess its therapeutic potential. Here we have compared the anti-inflammatory effect of quercetin-loaded microemulsion (QU-ME) and quercetin suspension (QU-SP) in an experimental model of airways allergic inflammation. Mice received daily oral doses of QU-ME (3 or 10mg/kg; in an oil-in-water microemulsion content 0.02:0.2:1 of lecithin:castor oil:Solutol HS15((R))), QU-SP [10mg/kg, in carboxymethylcellulose (CMC) 0.5% in water] or vehicle from the 18th to the 22nd day after the first immunization with ovalbumin (OVA). Dexamethasone was used as positive control drug. Every parameter was evaluated in the 22nd day (24h after the second OVA-challenge). We have also tried to assess by HPLC-MS a quercetin metabolite in the blood of rats treated with QU-SP or QU-ME. QU-ME was better orally absorbed when compared with QU-SP. Furthermore, oral administration of QU-SP failed to interfere with leukocyte recruitment, while QU-ME inhibited in a dose-dependent way, the eosinophil recruitment to the bronchoalveolar lavage fluid (BALF). QU-ME also significantly reduced both IL-5 and IL-4 levels, but failed to interfere with CCL11, IFN-gamma and LTB(4) levels. In addition, QU-ME oral treatment inhibited the nuclear transcription factor kappa B (NF-kappaB) activation, P-selectin expression and the mucus production in the lung. The present results show that QU-ME exhibits pronounced anti-inflammatory properties in a murine model of airways allergic inflammation and suggest that it might present therapeutic potential for the airways inflammatory diseases management.

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Background and purpose:  α‐Humulene and trans‐caryophyllene are plant sesquiterpenes with pronounced anti‐inflammatory properties. Here, we evaluated the effects of these compounds in an experimental model of airways allergic inflammation. Experimental approach:  Female BALB/c mice, sensitized to and challenged with ovalbumin received daily α‐humulene or trans‐caryophyllene (50 mg·kg−1, orally) or α‐humulene (1 mg·mL−1, by aerosol) as either a preventive (for 22 days) or therapeutic (from the 18th to the 22nd day) treatment. Dexamethasone or budesonide was used as a positive control drug. Inflammation was determined on day 22 post‐immunization by leukocyte recruitment, interleukin‐5 (IL‐5), CCL11, interferon‐γ (IFN‐γ) and leukotriene (LT)B4 levels in bronchoalveolar lavage fluid (BALF). In addition, transcription factors [nuclear factor κB (NF‐κB), activator protein 1 (AP‐1)] and P‐selectin in lung tissue were measured by immunohistochemistry and mucus secretion by histochemistry. Key results:  Preventive or therapeutic treatments with α‐humulene, but not with trans‐caryophyllene, significantly reduced the eosinophil recruitment to the BALF. In addition, α‐humulene recovery INF‐γ and reduced the IL‐5, CCL11 and LTB4 levels in BALF, as well as the IL‐5 production in mediastinal lymph nodes (in vitro assay). Furthermore, α‐humulene decreased the NF‐kB and the AP‐1 activation, the expression of P‐selectin and the increased mucus secretion in the lung. Conclusions and implications:  α‐Humulene, given either orally or by aerosol, exhibited marked anti‐inflammatory properties in a murine model of airways allergic inflammation, an effect that seemed to be mediated via reduction of inflammatory mediators, adhesion molecule expression and transcription factors activation. This article is part of a themed issue on Mediators and Receptors in the Resolution of Inflammation. To view this issue visit http://www3.interscience.wiley.com/journal/121548564/issueyear?year=2009