No abstract

(1) Patients with AAA have fewer atherosclerotic risk factors than do patients with AOD. (2) Patients with AAA and AOD have significantly different inflammatory activity. (3) The data supports the hypothesis that AAA and AOD are probably two different pathological entities.

Coeliac disease (CD), an inflammatory enteropathy, is believed to be caused by immune sensitivity to ingested gluten. T‐cell activation appears to be implicated in the disease although little is known regarding the role of T‐cell subsets, Th1/Th2, and the cytokines they secrete. Reverse transcription‐polymerase chain reaction was used to examine the mRNA expression of a wide profile of cytokines in intestinal and peripheral samples taken from active and inactive CD paediatric patients. Differential mRNA expression was observed for cytokines, between CD patients and controls, in both compartments. The percentage of samples expressing interleukin (IL)‐2, interferon (IFN)‐γ, tumor necrosis factor (TNF)‐β, IL‐10, IL‐1β, TNF‐α and transforming growth factor (TGF)‐β mRNA from active CD patients was higher than from controls. A prominent finding was the expression of both Th1 (IFN‐γ, IL‐2) and Th2 (IL‐4, IL‐10)‐associated cytokine transcripts in the same biopsies and peripheral blood cells from patients with active CD implying activation of Th0 cells. The expression of IL‐2 and IL‐4 mRNA was not observed in peripheral blood samples from inactive CD patients associating them with disease activity. These results are important to the understanding of the inflammatory process in CD while cytokine levels may prove to be relevant markers of disease activity.

Cellular hypoxia, characterizing tumors, ischemia, and inflammation induce recruitment of monocytes/macrophages, immobilize them at the hypoxic site, and alter their function. To migrate across the extracellular matrix and as part of their inflammatory functions, monocytes and macrophages secrete proteases, including matrix metalloproteinase-9 (MMP-9), whose expression is induced by proinflammatory cytokines [e.g., tumor necrosis factor alpha (TNF-alpha)]. We show that hypoxia (<0.3% O2 for 48 h) reduced the output of TNF-alpha-induced proMMP-9 by threefold (P < 0.01) in the U937 monocytic cell line and in primary human monocytes. TNF-alpha induced MMP-9 transcription by threefold, but no significant difference was observed in MMP-9 mRNA steady-state between normoxia and hypoxia, which inhibited the trafficking of proMMP-9 via secretory vesicles and increased the intracellular accumulation of proMMP-9 in the cells by 47% and 62% compared with normoxia (P < 0.05), as evaluated by zymography of cellular extracts and confocal microscopy, respectively. Secretion of proMMP-9 was reduced by the addition of cytochalazin B or nocodazole, which inhibits the polymerization of actin and tubulin fibers, or by the addition of the Rho kinase inhibitor Y27632, suggesting the involvement of the cytoskeleton and the Rho GTPases in the process of enzyme secretion. Furthermore, attachment of proMMP-9 to the cell membrane increased after hypoxia via its interactions with surface molecules such as CD44. In addition, the reduced migration of monocytes in hypoxia was shown to be mediated, at least partially, by secreted MMP-9. Thus, hypoxia post-translationally reduced the secreted amounts of proMMP-9 by using two mutually nonexclusive mechanisms: mostly, inhibition of cellular trafficking and to a lesser extent, attachment to the membrane.

Monocytes remodel the extracellular matrix (ECM) by secreting proteins composing the ECM such as fibronectin (FN) and degrading proteases such as matrix metalloproteinase-9 (MMP-9), which cleaves FN into fragments. The effects of FN and its fragmented products on the expression of monocyte MMP-9 are controversial and largely unknown. We showed that in human monocytes, the proinflammatory cytokine TNF-alpha induced MMP-9 secretion and increased fragmentation of FN into distinct fragments. When primary monocytes or the U937 monocytic cell line were incubated on a plastic substrate, plastic-coated with native FN, and plastic-coated with fragmented FN (frag-FN), native FN inhibited TNF-alpha-induced proMMP-9 secretion by twofold (P<0.01) compared with plastic or frag-FN. Exploration of the dynamics of inflammation by incubating cells sequentially on the three substrates showed that frag-FN opposed the inhibitory effect of native FN. Inhibition of proMMP-9 by native FN was exerted at the translational level, as no change in MMP-9 mRNA, intracellular protein accumulation, or proteomic degradation was observed, and when degradation was blocked, no de novo translation of MMP-9 could be measured. We also showed that the reduction of MMP-9 secretion by native FN was responsible for attenuated migration of U937 cells (P<0.05). We suggest that in the inflammatory tissue, intact, native FN has a homeostatic role in harnessing MMP-9 activity. However, as fragmented products accumulate locally, they alleviate the inhibition and enable faster migration of the monocytes through the degraded ECM.