(−)‐Epigallocatechin gallate (EGCG) is a potent antioxidant that is neuroprotective against ischemia‐induced brain damage. However, the neuroprotective effects and possible mechanisms of action of EGCG after hypoxia‐ischemia (HI) have not been investigated. Therefore, we used a modified “Levine” model of HI to determine the effects of EGCG. Wistar rats were treated with either 0.9% saline or 50 mg/kg EGCG daily for 1 day and 1 h before HI induction and for a further 2 days post‐HI. At 26‐days‐old, both groups underwent permanent left common carotid artery occlusion and exposure to 8% oxygen/92% nitrogen atmosphere for 1 h. Histological assessment showed that EGCG significantly reduced infarct volume (38.0±16.4 mm ³ ) in comparison to HI + saline (99.6±15.6 mm ³ ). In addition, EGCG significantly reduced total (622.6±85.8 pmol l ‐[ ³ H]citrulline/30 min/mg protein) and inducible nitric oxide synthase (iNOS) activity (143.2±77.3 pmol l ‐[ ³ H]citrulline/30 min/mg protein) in comparison to HI+saline controls (996.6±113.6 and 329.7±59.6 pmol l ‐[ ³ H]citrulline/30 min/mg protein for total NOS and iNOS activity, respectively). Western blot analysis demonstrated that iNOS protein expression was also reduced. In contrast, EGCG significantly increased endothelial and neuronal NOS protein expression compared with HI controls. EGCG also significantly preserved mitochondrial energetics (complex I‐V) and citrate synthase activity. This study demonstrates that the neuroprotective effects of EGCG are, in part, due to modulation of NOS isoforms and preservation of mitochondrial complex activity and integrity. We therefore conclude that the in vivo neuroprotective effects of EGCG are not exclusively due to its antioxidant effects but involve more complex signal transduction mechanisms.

Objective: To profile monosodium urate monohydrate (MSU) crystal–recruited monocyte inflammatory function during the course of in vivo differentiation, in a murine model of peritoneal MSU crystal–induced inflammation.Methods: C57BL/6J mice were injected intraperitoneally with MSU crystals, and the peritoneal cells were harvested at different time points. The MSU crystal–recruited monocyte/macrophage population was analyzed for the expression of differentiation and activation markers, cytokine production following MSU crystal restimulation ex vivo and in vivo, expression of NLRP3‐associated proteins (ASC, caspase 1) and pro–interleukin‐1β (proIL‐1β), and phagocytic capacity.Results: Monocytes recruited 8 hours after MSU crystal stimulation (F4/80^lowGr‐1^int7/4+) exhibited poor phagocytic capacity, expressed low levels of proIL‐1β, and failed to produce proinflammatory cytokines in response to MSU crystal restimulation. In the absence of MSU crystal restimulation, differentiating monocytes produced low levels of transforming growth factor β1 ex vivo, and this was abrogated following MSU crystal restimulation. Over time these cells developed a proinflammatory phenotype in vivo, characterized by the production of IL‐1β, tumor necrosis factor α, IL‐6, CCL2 (monocyte chemotactic protein 1), and CXCL1 (cytokine‐induced neutrophil chemoattractant) following ex vivo MSU crystal restimulation, and leading to IL‐1β production and cell infiltration following MSU crystal rechallenge in vivo. Proinflammatory function was associated with differentiation toward a macrophage phenotype (F4/80^highGr‐1–7/4–), an increase in phagocytic capacity, and an increase in the expression of proIL‐1β.Conclusion: MSU crystal–recruited monocytes differentiate into proinflammatory M1‐like macrophages in vivo. This proinflammatory macrophage phenotype is likely to play a key role in perpetuating inflammation in gouty arthritis in the presence of ongoing deposition of fresh MSU crystals.

Objectives MicroRNAs (miRNA) are small non-coding RNAs that function as post-transcriptional repressors of gene expression. We hypothesised that miRNA regulate gene expression of proinflammatory cytokines in response to monosodium urate (MSU) crystals. Methods We stimulated human monocytic THP-1 cells with MSU crystals and examined miRNA and proinflammatory cytokine gene expression. The effects of miR-146a overexpression were examined by transfecting THP-1 cells with miR-146a precursor. miR-146a expression was examined in the urate peritonitis model, in peripheral blood mononuclear cells from people with gout and control participants, and in gouty tophus samples. Results MSU crystals increased miR-146a expression in THP-1 cells, but not other miRNA implicated in interleukin (IL)-1β regulation. Overexpression of miR-146a expression reduced MSU crystal-induced IL-1β, tumour necrosis factor-α (TNFα), monocyte chemoattractant protein-1 (MCP-1) and IL-8 gene expression. In the urate peritonitis model, reduced miR-146a expression was observed during the acute inflammatory response to MSU crystal injection. In people with intercritical gout, peripheral blood mononuclear cells expressed significantly higher levels of miR-146a, compared with normouricaemic and hyperuricaemic control participants and those with acute gout flares. Expression of miR-146a was also observed in all tophus samples. Conclusions Collectively, these data suggest that miR-146a is a transcriptional brake that is lost during the acute inflammatory response to MSU crystals.

Objectives. Neutrophils traffic into and have the capacity to generate kinins in SF of RA patients. The aim of this study was to assess the expression of kallikreins, kininogens and kinin receptors in circulating and SF neutrophils, as well as synovial tissue of RA patients, and to assess kinin generation in SF. Methods. Neutrophils were isolated from blood and SF of RA patients and blood of healthy volunteers. Expression of kallikreins, kininogens and kinin receptors in neutrophils and synovial tissue was assessed by immunocytochemistry using specific antibodies, with visualization by brightfield and confocal microscopy. Levels of basal and generated kinins in SF of RA patients were measured by ELISA. Results. Kinin labelling was significantly reduced, indicating the loss of the kinin moiety from kininogen on circulating (P < 0.001) and SF neutrophils (P < 0.05) of RA patients. Immunolabelling of tissue kallikrein was also decreased, whereas kinin B₁ and B₂ receptor expression was increased in circulating and SF neutrophils of RA patients. Immunolabelling of kallikreins and kinin receptor proteins was similar in RA and normal synovial tissues. The basal kinin level in SF of RA patients was 5.7 ± 6.1 ng/ml and the mean concentration of kinins generated in vitro was 80.6 ± 56.3 ng/ml. The capacity for kinin generation was positively correlated with measures of disease activity. Conclusions. Kallikrein–kinin proteins on neutrophils play an important role in kinin generation and the pathophysiology of RA. Specific kallikrein and kinin receptor antagonists may be useful as IA therapies for inflamed joints.

The potential of fruit proanthocyanidins to modulate airway inflammation through interactions with immune cells and the microbiome.