Background and purpose: Matrix metalloproteinases (MMPs) have been implicated in joint tissue destruction in arthritis. However, MMPs have not been assigned a role in joint pain. We investigated the ability of BaP1, a metalloproteinase from Bothrops asper snake venom, with structural homology to MMPs, to induce joint hypernociception. Experimental approach: Animals received intra-articular (i.art.) BaP1. Hypernociception was assessed using the rat-knee joint articular incapacitation test. Cell influx, prostaglandin E 2 (PGE 2 ), and TNF-a levels were assessed in joint exudates following BaP1 injection. Key results: BaP1 (5 mg per joint) provoked hypernociception between 1 and 6 h after i.art. injection. Cell influx, mostly neutrophils, was maximal 3 h after BaP1 i.art. injection. BaP1 also led to increase in PGE 2 and TNF-a levels in the joint exudates. Pretreatment with either indomethacin (4 mg.kg À1 i.p.) or with an anti-TNF-a antiserum (i.art.) significantly inhibited both BaP1-induced joint hypernociception and cell influx. In isolated rat peritoneal macrophages, BaP1 increased cyclooxygenase (COX)-2 expression, while not altering that of COX-1. Conclusions and implications: This is the first demonstration that a metalloproteinase promotes joint hypernociception. This effect involves local release of PGE 2 and TNF-a. BaP1-induced increase in PGE 2 is associated to increased COX-2 expression in macrophages. Blocking PGE 2 or TNF-a inhibits BaP1-induced hypernociception. In addition to unravelling a hitherto unknown mechanism whereby TNF blockade provides analgesia in arthritis, the data show, for the first time that MMPs are involved in inflammatory joint hypernociception and induce COX-2 expression.

BACKGROUND AND PURPOSEWe investigated the effect of the phosphodiesterase-5 inhibitor, tadalafil, on the acute hypernociception in rat models of arthritis. EXPERIMENTAL APPROACHRats were treated with either an intra-articular injection of zymosan (1 mg) or surgical transection of the anterior cruciate ligament (as an osteoarthritis model). Controls received saline intra-articular or sham operation respectively. Joint pain was evaluated using the articular incapacitation test measured over 6 h following zymosan or between 4 and 7 days after anterior cruciate ligament transection. Cell counts, tumour necrosis factor-a (TNF-a), interleukin-1 (IL-1), and the chemokine, cytokine-induced neutrophil chemoattractant-1 (CINC-1) were measured in joint exudates 6 h after zymosan. Groups received tadalafil (0.02-0.5 mg·kg -1 per os) or saline 2 h after intra-articular zymosan. Other groups received the m-opioid receptor antagonist naloxone or the cGMP inhibitor 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ) before tadalafil. KEY RESULTSTadalafil dose-dependently inhibited hypernociception in zymosan and osteoarthritis models. In zymosan-induced arthritis, tadalafil significantly decreased cell influx and TNF-a release but did not alter IL-1 or CINC-1 levels. Pretreatment with ODQ but not with naloxone prevented the anti-inflammatory effects of tadalafil. CONCLUSIONS AND IMPLICATIONSTherapeutic oral administration of tadalafil provided analgesia mediated by guanylyl cyclase and was independent of the release of endogenous opioids. This effect of tadalafil was associated with a decrease in neutrophil influx and TNF-a release in inflamed joints.

Background and purpose:We investigated the effect of nitric oxide synthase (NOS) inhibition on polymorphonuclear cell (PMN) influx in zymosan or lipopolysaccharide (LPS)-induced arthritis and peritonitis. Experimental approach: Wistar rats received intra-articular (i.art.) zymosan (30-1000 mg) or LPS (1-10 mg). Swiss C57/Bl6 mice genetically deficient in intercellular adhesion molecule-1 (ICAM-1 and b2-integrin -/-mice with zymosan-arthritis, while not altering PMN influx into the peritoneum of mice with zymosanperitonitis. Conclusions and implications:Nitric oxide has a dual modulatory role on PMN influx into joint and peritoneal cavities that is stimulus-and species-independent. Differences in local release of LTB4 and in expression of ICAM-1 and b2-integrin account for this dual role of NO on PMN migration.

Pemphigus is an inflammatory autoimmune disorder of the skin. Nitric oxide (NO) is an inflammatory mediator linked to a variety of physiological and pathophysiological phenomena that include skin tumors, psoriasis, urticaria, and atopic dermatitis. Inflammatory cells present in pemphigus lesions are important sources of NO production. We investigated whether NO is involved in pemphigus. A prospective cohort study was conducted at the Dermatology Service of the Hospital Universitário Walter Cantídio of the Federal University of Ceará. All patients seen at the outpatient clinic between August 2000 and July 2001, with a clinically and histologically confirmed diagnosis of pemphigus were included. The median age was 42.5 years (range: 12-69 years) with a male to female ratio of 3:2. Total serum nitrite levels, used as a marker for NO production, were determined by the Griess reaction. Skin biopsies from pemphigus and breast surgery (control) patients were used for the detection of the inducible NO synthase (iNOS) by immunohistochemistry. Twenty-two (22) patients with pemphigus and eight (8) controls who did not differ in demographic characteristics were included. Total serum nitrite levels were significantly higher (>7 µmol/L) in pemphigus patients compared to controls (<6 µmol/L), regardless of the severity of the clinical activity of pemphigus (P < 0.0001). All pemphigus biopsies presented increased immunostaining for iNOS that was not detected in normal skin samples. These data are the first to demonstrate that pemphigus patients display increased serum NO levels that are associated with increased iNOS expression in the affected skin.

We aimed to describe the serum levels of 25-hydroxyvitamin D (25OHD) in juvenile idiopathic arthritis (JIA) patients living in a low-latitude (3°43'S) region. Fifty JIA patients, 31 (62 %) female, seen between May 2012 and April 2013 in the northeast of Brazil had clinical data and serum collected for determination of 25OHD and parathyroid hormone (PTH) using a chemiluminescent ELISA; 20 age- and sex-matched controls were used for comparison. Mean age was 13.4 ± 4 years. Twenty-five (50 %), 15 (30 %), 4 (8 %), 4 (8 %), and 2 (4 %) patients were of the polyarticular, oligoarticular, systemic, enthesitis-related, and undifferentiated categories, respectively. Mean 25OHD was 31.6 ± 10 and 30.4 ± 5.7 ng/mL in patients and controls (P > 0.05), respectively; PTH was normal in JIA and controls; 25OHD was similar regardless of JIA category, disease activity, or severity measured by JADAS-27, CHAQ, or presence of joint deformities. Twenty-six (52 %), 20 (40 %), and 4 (8 %) patients were considered to have optimal, sufficient, and deficient 25OHD levels, respectively, whereas 11 (52 %) and 10 (48 %) controls had optimal and sufficient 25OHD. Ethnicity, body mass index, seasonal variation, and use of steroids did not influence 25OHD levels. This is the first study on 25OHD levels in JIA patients living in a low-latitude region, showing the lowest prevalence of vitamin D deficiency ever reported. Serum 25OHD was similar in JIA and controls and did not vary regardless of JIA category or severity.