FK506 attenuates developing and established joint inflammation and suppresses interleukin 6 and nitric oxide expression in bacterial cell wall induced polyarthritis.

OBJECTIVE: To determine the efficacy of therapeutic administration of FK506 (Tacrolimus) in suppressing developing and established joint inflammation, proinflammatory cytokine expression, and nitric oxide (NO) production in peptidoglycan-polysaccharide (PG/PS) induced experimental polyarthritis in rats. METHODS: Chronic joint inflammation was induced by intraperitoneal injection of PG/PS, and joint inflammation was quantified using arthritis index and paw volume. Serum and joint levels of interleukin 6 (IL-6) were measured by bioassay and Western blot analysis respectively, and serum levels of NO production were determined by the Griess procedure and the expression of the inducible isoform of nitric oxide synthase (i-NOS) in the joints was determined by Western blot analysis. RESULTS: Arthritis induced by PG/PS is biphasic, progressing through an initial acute phase and a remission phase, which is followed by a persistent chronic phase. Daily administration of FK506 initiated during the remission phase significantly attenuated the onset and development of chronic joint inflammation. We observed a significant reduction in joint inflammation and swelling, an apparent suppression of pannus development, and minimal erosive damage to the articular cartilage and subchondral bone. Fully established chronic joint inflammation was also ameliorated by daily administration of FK506. Joint swelling and inflammation was significantly reduced by 5 days post-treatment with FK506 and the erosive activity associated with the pannus appeared diminished. The elevated expression of IL-6 and NO characteristic of chronic joint inflammation in the serum and in joint tissue was significantly reduced by FK506 treatment. CONCLUSION: Therapeutic administration of FK506 has a profound antiinflammatory effect on the development of the chronic, erosive arthritis induced by PG/PS. This attenuation in joint inflammation was associated with suppression of IL-6 and NO production systemically and locally in the joints. Our data suggest that FK506 may be effective in the treatment of chronic joint inflammation associated with rheumatoid arthritis.

Cytokine and nitric oxide production in the acute phase of bacterial cell wall-induced arthritis.

We have investigated the temporal relationship among proinflammatory cytokine expression, nitric oxide (NO) production and joint inflammation in the acute phase of bacterial cell wall-derived peptidoglycan polysaccharide (PG/PS)-induced arthritis. Acute joint inflammation was induced in female LEW/N rats by a single intraperitoneal injection of PG/PS. Arthritis index and paw volume were quantified and joint histopathology was evaluated during acute joint inflammation (0-10 days). Tumor necrosis factor (TNF), interleukin-1 (IL-1) and interleukin-6 (IL-6) were determined by bioassay whereas nitric oxide (NO) was quantified by measuring serum nitrate/nitrite levels via the Griess procedure. We found that serum levels of TNF and serum IL-1 preceded the increase in IL-6 and NO production. Furthermore, the production of these proinflammatory cytokines and NO preceded bone erosion and osteoclast activity. Erosion of subchondral bone preceded pannus formation and cellular synovitis in the acute phase of PG/PS-induced arthritis. The temporal expression of TNF, IL-1, IL-6 and NO suggest a cascade of inflammatory mediators in which monocytes and macrophages respond to PG/PS with enhanced synthesis of TNF and IL-1, which may in turn promote the synthesis of IL-6 and NO. We postulate that one or more of these inflammatory events are responsible for initiating the subchondral bone erosion observed in acute joint inflammation.

A comparative analysis of two models of colitis in rats.

Two models of colitis produced in rats that have received significant attention over the past few years are the acetic acid and trinitrobenzene sulfonic acid (TNBS) models. The objective of this study was to quantify and compare the temporal relationship among mucosal permeability, epithelial injury, and inflammation induced by acetic acid, ethanol (vehicle), ethanol plus TNBS (unbuffered, pH 1.0), and ethanol plus TNBS (pH 7.4). Data obtained show that the inflammation induced by these four irritants results from caustic injury to the colonic epithelium and interstitium as measured by the rapid and dramatic increases in mucosal permeability and tissue water content as well as by histological analysis. The injurious nature of TNBS was confirmed in a separate series of studies showing that buffered TNBS (pH 7.4), in the absence of ethanol, is toxic to cultured rat intestinal epithelial cell monolayers. Only after 1-2 days of the initial insult, were signs of classical inflammation observed, including increases in colonic myeloperoxidase activity (neutrophil infiltration) and colon weight as well as hyperemia and mucosal ulcerations. Although ethanol plus TNBS (pH 1.0 or 7.4) tended to produce higher mucosal permeabilities (epithelial cell injury) at 1-2 weeks after the enemas than acetic acid or ethanol groups, only the ethanol plus TNBS (pH 7.4) permeabilities were found to be significantly enhanced. In addition, all four groups showed significant elevations in colonic myeloperoxidase activity and colon weight at 1-2 weeks after enema. It is suggested that these models of colitis are useful to study events that occur at the time of inflammation and repair. However, these models may have significant limitations in understanding events that initiate inflammation of the intestine in human inflammatory bowel disease.

Misoprostol accelerates colonic mucosal repair in acetic acid-induced colitis.

The objectives of this study were 1) to determine whether misoprostol (MISO) (prostaglandin E1 analog) pretreatment protects the colonic mucosa from the injurious effects of acetic acid by attenuating the initial injury or by enhancing the rate of repair and 2) to assess the relationship between the protective effect of MISO pretreatment and mucosal ornithine decarboxylase activity in the inflamed colon. We found that the intrarectal administration of acetic acid caused rapid and extensive injury to the colonic mucosa, such that mucosal permeability increased 88-, 75-, 26-, 7.5- and 9.3-fold at 1, 2, 6, 24 and 48 hr after the enema, respectively. Intrarectal pretreatment with 50 micrograms of MISO for 30 min did not attenuate the increase in mucosal permeability at 1 hr after enema; however, it did significantly reduce mucosal permeability by 50 to 60% at 2, 6 and 48 hr after enema. We also demonstrated that acetic acid produced an 8.4-fold increase in colonic myeloperoxidase activity and a 1.8-fold increase in colonic weight at 48 hr after enema. MISO significantly reduced the increases in both myeloperoxidase activity and colon weight. Ornithine decarboxylase activity in the descending colon of vehicle-pretreated animals increased significantly only at 24 hr after the acetic acid enema. In addition, MISO pretreatment followed by acetic acid enema resulted in significantly higher ornithine decarboxylase activities in the descending colon at 2 and 6 hr, compared with the vehicle plus acetic acid and MISO plus saline groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Misoprostol attenuates acetic acid-induced increases in mucosal permeability and inflammation: role of blood flow.

The objectives of this study were 1) to quantify the effects of misoprostol (Miso; prostaglandin E1 analogue) on acetic acid-induced increases in mucosal permeability and inflammation; 2) to determine what effect acetic acid, Miso, or the combination of Miso plus acetic acid has on colonic blood flow; and 3) to assess whether the protective effect of Miso may be attributable to its vasodilatory properties. We found that intrarectal administration of acetic acid produced a 6.4-fold increase in colonic myeloperoxidase activity (an index of granulocyte infiltration), an 8.2-fold increase in mucosal permeability, a 1.6-fold increase in colonic weight, and a 6.8% decrease in body weight 48 h after enema. Miso pretreatment significantly attenuated the increases in colonic myeloperoxidase activity, mucosal permeability, and colon weight as well as prevented the loss of body weight. In a different series of experiments, we found that blood flow in the descending, transverse, and ascending colon increased 2.5- to 3.5-fold immediately after the acetic acid enema; however, it returned to control values at 1 and 4 h after enema. Miso pretreatment, followed by acetic acid, resulted in a further increase (2.5-fold) in blood flow in the descending colon 1 h after enema compared with acetic acid alone. This Miso-induced increase in blood flow at 1 h could not account for its protective effect inasmuch as colonic mucosal permeability (i.e., injury) in Miso-pretreated animals was not significantly different from values obtained in animals pretreated with vehicle and then given the enema.

Inflammation-induced intestinal hyperemia in the rat: role of neutrophils.

Both experimental colitis and human inflammatory bowel disease are characterized by an increased colonic blood flow. The objective of this study was to define the role of neutrophils in the colonic hyperemia associated with acetic acid-induced colitis in rats. One, two, and five days after the acetic acid enema, the colon was separated into five segments. Regional blood flow to each segment was measured using the radioactive microsphere technique. Tissue-associated myeloperoxidase activity was used as an index of neutrophil infiltration. Rectal blood flow and myeloperoxidase activity increased progressively after the acetic acid enema. At 5 days there were 3.9- and 4.6-fold increases in myeloperoxidase activity and blood flow, respectively. Comparable changes were noted in all bowel segments. The results suggest a temporal relationship between colonic blood flow and the extent of neutrophil infiltration. To assess directly the role of circulating and infiltrated neutrophils as mediators of the colitis-induced hyperemia, animals were rendered neutropenic approximately 8 h before the enema and neutropenia was maintained for another 24 h. Neutropenia did not modify the colitis-induced intestinal hyperemia normally observed at 24 h. We conclude from these findings that vasoactive agents derived from neutrophils do not mediate the increased colonic blood flow in this model of ulcerative colitis.

Hemorrhagic shock-induced bacterial translocation is reduced by xanthine oxidase inhibition or inactivation.

Experiments were performed to determine whether bacterial translocation (BT) after hemorrhagic shock is due to a reperfusion injury mediated by xanthine oxidase-derived oxidants. Rats were subjected to 30 minutes of shock (30 mm Hg) followed by reinfusion of shed blood. Twenty-four hours after hemorrhage and reinfusion, the mesenteric lymph node, liver, and spleen were harvested from each animal for bacterial culture, and the ileum and cecum were examined histologically. Sham-shocked (control) rats were instrumented, but blood was not withdrawn. The incidence of BT was higher in the shocked rats (61%) than in the sham-shocked animals (7%) (p less than 0.01). Allopurinol (50 mg/kg, administered orally), a competitive inhibitor of xanthine oxidase, reduced the incidence of shock-induced BT to 14% (p = 0.02). Similarly, rats fed a tungsten-supplemented molybdenum-free diet, which inactivates xanthine oxidase, reduced shock-induced BT to 10% (p = 0.02). The histologic damage cause by hemorrhagic shock was prevented by blocking xanthine oxidase activity. Thus hemorrhagic shock-induced bacterial translocation from the gut appears to be mediated by oxidants generated by activation of the xanthine oxidase system.