Lack of effects of acemetacin on signalling pathways for leukocyte adherence may explain its gastrointestinal safety

Synergistic protective effects between docosahexaenoic acid and omeprazole on the gastrointestinal tract in the indomethacin-induced injury model

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most commonly used drugs due to their antipyretic, anti-inflammatory, and analgesic properties. However, NSAIDs can cause adverse reactions, mainly gastrointestinal damage. Omeprazole (OMP) exhibits gastroprotective activity, but its protection is limited at the intestinal level. For this reason, it is essential to utilize a combination of therapies that provide fewer adverse effects, such as the combined treatment of OMP and docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid with anti-inflammatory, analgesic, and gastroprotective activities. The objective of this study was to evaluate the pharmacological interaction between DHA and OMP in a murine model of indomethacin-induced gastrointestinal damage. The gastroprotective and enteroprotective effects of DHA (0.3-10 mg/kg, p.o.), OMP (1-30 mg/kg, p.o.), or the combination treatment of both compounds (3-56.23 mg/kg, p.o.) were evaluated in the indomethacin-induced gastrointestinal damage model (30 mg/kg, p.o.). Since DHA and OMP exhibited a protective effect in a dose-responsive fashion, the ED₃₀ for each individual compound was determined and a 1:1 combination of DHA and OMP was tested. Isobolographic analysis was used to determine any pharmacodynamic interactions. Since the effective experimental dose ED₃₀ (Zexp) of the combined treatment of DHA and OMP was lower than the theoretical additive dose (Zadd; p < .05) in both the stomach and small intestine their protective effects were considered synergistic. These results indicate that the synergistic protective effects from combined treatment of DHA and OMP could be ideal for mitigating damage generated by NSAIDs at the gastrointestinal level.

Anti-inflammatory, antioxidant, and gaso-protective mechanism of 3α-hydroxymasticadienoic acid and diligustilide combination on indomethacin gastric damage

The co-administration of 3α-hydroxymasticadienoic acid (3α-OH MDA) and diligustilide (DLG) generates a synergist gastroprotective effect on indomethacin-induced gastric damage. However, the related protective activities of the compounds alone (or in combination) remain unclear. In the present study, we evaluated the anti-inflammatory and antioxidative activities, as well as the potential modulation of important gasotransmitters of each compound individually and in combination using the indomethacin-induced gastric damage model. Male Wistar rats were treated orally with the 3α-OH MDA, DLG, or their combination (at a fixed ratio of 1:1, 1:3, and 3:1) 30 min before the generation of gastric mucosal lesions with indomethacin (30 mg/kg, p.o.). Three hours later, the gastric injury (mm²) was determined. Results from these experiments indicate, in addition to maintaining basal levels of PGE₂, the gastroprotective effect of the pre-treatment with 3α-OH MDA (70%), DLG (81%), and their combination (72%) which was accompanied by significant decreases in leukocyte recruitment, as well as decreases in TNF-α and LTB₄ gastric levels (p < 0.05). We also found that the pre-treatment maintains the basal antioxidant enzyme activities (SOD) and gastric NO and H₂S production even in the presence of indomethacin (p < 0.05). In conclusion, when 3α-OH MDA-DLG is given at a 1:1 combination ratio, the gastroprotective effect and the inflammatory, antioxidant, and gaso-modulation properties are not different from those of treatments using the maximum doses of each compound, revealing that this combination produces promising results for the treatment of gastric ulcers.

A novel class of copper(II)- and zinc(II)-bound non-steroidal anti-inflammatory drugs that inhibits acute inflammation in vivo

Background

The ability of Zn(II) and Cu(II) metal complexes of non-steroidal anti-inflammatory drugs (NSAIDs) to inhibit acute arterial inflammation in vivo has been studied.

Results

When acute vascular inflammation was induced in normocholesterolemic New Zealand White rabbits by inserting a non-occlusive silastic collar around the common carotid artery, a single oral dose of Cu(II)-indomethacin (Cu(II)Indo, 3 mg/kg) administered by laparotomy achieved a 67 % (8.2 ± 1.7 vs. 2.7 ± 0.4 image units, p < 0.05) reduction in endothelial expression of vascular cell adhesion molecule-1 (VCAM-1) but did not inhibit endothelial intercellular adhesion molecule (ICAM-1) expression significantly. Treatment with Cu(II)-acemetacin (Cu(II)ACM, 3 mg/kg) led to a profound 88 % (8.2 ± 1.7 vs. 1.0 ± 0.5 image units, p < 0.01) reduction in endothelial VCAM-1 expression but did not inhibit ICAM-1 expression, while treatment with Zn(II)-acemetacin (Zn(II)ACM, 3 mg/kg) led to an 84 % (19.3 ± 1.0 vs. 3.1 ± 1.2 image units, p < 0.01) reduction in endothelial ICAM-1 expression and did not inhibit VCAM-1 expression. No adverse gastric, hepatic or renal effects were observed in treated animals.

Conclusion

These findings provide the “proof of concept” that this novel class of drug, where there is complexation of NSAIDs with metal ions, has substantial anti-inflammatory effects in an animal model of acute vascular inflammation with the possibility of low rates of adverse effects.

Proresolution effects of hydrogen sulfide during colitis are mediated through hypoxia-inducible factor-1α

During a course of colitis, production of the gaseous mediator hydrogen sulfide (H2S) is markedly up-regulated at sites of mucosal damage and contributes significantly to healing and resolution of inflammation. The signaling mechanisms through which H2S promotes resolution of colitis are unknown. We hypothesized that the beneficial effects of H2S in experimental colitis are mediated via stabilization of hypoxia-inducible factor (HIF)-1α. The hapten dinitrobenzene sulfonic acid was used to induce colitis in rats and mice. This resulted in an elevated expression of the H2S-producing enzyme, cystathionine γ-lyase (CSE), and HIF-1α at sites of mucosal ulceration, and the expression of these 2 enzymes followed a similar pattern throughout the course of colitis. This represented a functionally important relationship because the loss of CSE-derived H2S production led to decreased HIF-1α stabilization and exacerbation of colitis. Furthermore, application of an H2S-releasing molecule, diallyl disulfide (DADS), stabilized colonic HIF-1α expression, up-regulated hypoxia-responsive genes, and reduced the severity of disease during peak inflammation. Importantly, the ability of DADS to promote the resolution of colitis was abolished when coadministered with an inhibitor of HIF-1α in vivo (PX-478). DADS was also able to maintain HIF-1α expression at a later point in colitis, when HIF-1α levels would have normally returned to control levels, and to enhance resolution. Finally, we found that HIF-1α stabilization inhibited colonic H2S production and may represent a negative feedback mechanism to prevent prolonged HIF-1α stabilization. Our findings demonstrate an important link between H2S and HIF-1α in the resolution of inflammation and injury during colitis and provide mechanistic insights into the therapeutic value of H2S donors.

Impaired hydrogen sulfide synthesis and IL-10 signaling underlie hyperhomocysteinemia-associated exacerbation of colitis

Vitamin B deficiencies, which can lead to hyperhomocysteinemia (Hhcy), are commonly reported in patients with inflammatory bowel disease (IBD) and may be a causative underlying factor. However, the mechanism for this effect is not known. Hydrogen sulfide (H2S) is a gaseous mediator that promotes tissue repair and resolution of inflammation. In experimental colitis, a marked increase in colonic H2S synthesis drives ulcer healing and resolution of inflammation. Because H2S synthesis is in part dependent upon enzymes that require vitamin B6 as a cofactor, we tested the hypothesis that Hhcy in rodent models would increase the susceptibility to colitis. In all three models tested, diet-induced Hhcy significantly exacerbated colitis. The usual elevation of colonic H2S synthesis after induction of colitis was absent in all three models of colitis. Administration of an H2S donor to Hhcy rats significantly decreased the severity of colitis. Compared with wild-type mice, interleukin (IL) 10-deficient mice on a normal diet had decreased levels of colonic H2S synthesis, a 40% increase in serum homocysteine, and a phenotype similar to wild-type mice with Hhcy. IL-10-deficient mice fed the vitamin B-deficient diet exhibited more severe colonic inflammation, but the normal elevation of colonic H2S synthesis was absent. Administration of IL-10 to the IL-10-deficient mice restored colonic H2S synthesis and significantly decreased serum homocysteine levels. These results suggest that the exacerbation of colitis in Hhcy is due in part to impaired colonic H2S synthesis. Moreover, IL-10 plays a novel role in promoting H2S production and homocysteine metabolism, which may have therapeutic value in conditions characterized by Hhcy.

Up-regulation of Annexin-A1 and lipoxin A(4) in individuals with ulcerative colitis may promote mucosal homeostasis

Background

One of the characteristics of an active episode of ulcerative colitis (UC) is the intense mucosal infiltration of leukocytes. The pro-resolution mediators Annexin-A1 (AnxA1) and lipoxin A₄ (LXA₄) exert counter-regulatory effects on leukocyte recruitment, however to date, the dual/cumulative effects of these formyl peptide receptor-2 (FPR2/ALX) agonists in the context of human intestinal diseases are unclear. To define the contribution of these mediators, we measured their expression in biopsies from individuals with UC.

Methods

Colonic mucosal biopsies were collected from two broad patient groups: healthy volunteers without (‘Ctrl’ n = 20) or with a prior history of UC (‘hx of UC’ n = 5); individuals with UC experiencing active disease (‘active’ n = 8), or in medically-induced remission (‘remission’ n = 16). We assessed the mucosal expression of LXA₄, AnxA1, and the FPR2/ALX receptor in each patient group using a combination of fluorescence microscopy, biochemical and molecular analyses.

Results

Mucosal expression of LXA₄ was elevated exclusively in biopsies from individuals in remission (3-fold, P<0.05 vs. Ctrl). Moreover, in this same group we observed an upregulation of AnxA1 protein expression (2.5-fold increase vs. Ctrl, P<.01), concurrent with an increased level of macrophage infiltration, and an elevation in FPR2/ALX mRNA (7-fold increase vs. Ctrl, P<.05). Importantly, AnxA1 expression was not limited to cells infiltrating the lamina propria but was also detected in epithelial cells lining the intestinal crypts.

Conclusions

Our results demonstrate a specific up-regulation of this pro-resolution circuit in individuals in remission from UC, and suggest a significant role for LXA₄ and AnxA1 in promoting mucosal homeostasis.

Proton pump inhibitors exacerbate NSAID-induced small intestinal injury by inducing dysbiosis

BACKGROUND & AIMS

Proton pump inhibitors (PPIs) and nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most commonly used classes of drugs, with the former frequently coprescribed to reduce gastroduodenal injury caused by the latter. However, suppression of gastric acid secretion by PPIs is unlikely to provide any protection against the damage caused by NSAIDs in the more distal small intestine.

METHODS

Rats were treated with antisecretory doses of omeprazole or lanzoprazole for 9 days, with concomitant treatment with anti-inflammatory doses of naproxen or celecoxib on the final 4 days. Small intestinal damage was blindly scored, and changes in hematocrit were measured. Changes in small intestinal microflora were evaluated by denaturing gradient gel electrophoresis and reverse-transcription polymerase chain reaction.

RESULTS

Both PPIs significantly exacerbated naproxen- and celecoxib-induced intestinal ulceration and bleeding in the rat. Omeprazole treatment did not result in mucosal injury or inflammation; however, there were marked shifts in numbers and types of enteric bacteria, including a significant reduction (∼80%) of jejunal Actinobacteria and Bifidobacteria spp. Restoration of small intestinal Actinobacteria numbers through administration of selected (Bifidobacteria enriched) commensal bacteria during treatment with omeprazole and naproxen prevented intestinal ulceration/bleeding. Colonization of germ-free mice with jejunal bacteria from PPI-treated rats increased the severity of NSAID-induced intestinal injury, as compared with mice colonized with bacteria from vehicle-treated rats.

CONCLUSIONS

PPIs exacerbate NSAID-induced intestinal damage at least in part because of significant shifts in enteric microbial populations. Prevention or reversal of this dysbiosis may be a viable option for reducing the incidence and severity of NSAID enteropathy.

Muc-2-deficient mice display a sex-specific, COX-2-related impairment of gastric mucosal repair

Mucus is known to contribute significantly to the prevention and repair of mucosal damage throughout the gastrointestinal tract. Although not normally expressed in the stomach, mucin-2 (MUC-2, encoded by the MUC2 gene) is expressed in certain disease states. The aim of this study was to determine in a mouse model whether the absence of Muc-2 would result in impaired susceptibility to and healing of gastric mucosal injury. Acute gastric damage was induced in mice deficient in Muc-2 and in wild-type controls, through oral administration of indomethacin. Chronic gastric ulcers were induced by serosal application of acetic acid. The extent of injury and the extent of healing of the damage over time were examined in both models. Indomethacin administration caused similar levels of gastric damage in Muc-2-deficient and wild-type mice, but the erosions healed more slowly in the former. Acetic acid-induced gastric ulcers were initially similar in size in Muc-2-deficient and wild-type mice of both sexes, but ulcer healing was significantly impaired in male Muc-2-deficient mice. Induction of cyclooxygenase-2 in the stomach, in response to indomethacin- or acetic acid-induced ulceration, was significantly reduced in male Muc-2-deficient mice. This phenomenon, and the sex specificity, was also apparent in bone marrow-derived macrophages stimulated with endotoxin. These results demonstrate a marked impairment of gastric mucosal repair in male Muc-2-deficient mice that may be related to an insufficient induction of cyclooxygenase-2, an enzyme known to contribute to mucosal repair.

Synergistic effect of the interaction between naproxen and citral on inflammation in rats

The combination of non-steroidal anti-inflammatory drugs with herbs having analgesic effects can increase their antinociceptive activity and limit their side effects. The aim of the present study was to examine the effects on inflammation and gastric injury in rats resulting from the interaction between naproxen and citral. Naproxen, citral, or fixed-dose naproxen-citral combinations were administered orally and their anti-inflammation (carrageenan-induced paw edema) and gastric damage were assessed in rats. The pharmacological interaction type was evaluated by the isobolographic analysis. Naproxen, citral, or combinations of naproxen and citral produced anti-inflammatory effects. The sole administration of naproxen produced significant gastric damage, but this effect was not obtained with either citral or combinations. ED(30) values were estimated for the individual drugs, and isobolograms were constructed. The derived theoretical ED(30) for the anti-inflammatory effect was 504.4 mg/kg; this was significantly higher than the observed experimental value (190.6 mg/kg). These results indicate that a synergistic interaction underlies the anti-inflammatory effect. The data suggests that the naproxen-citral combination can interact and to produce minor gastric damage and may have therapeutic advantages for the clinical treatment of inflammation.

A pro-resolution mediator, prostaglandin D(2), is specifically up-regulated in individuals in long-term remission from ulcerative colitis

Patients with ulcerative colitis (UC) experience unpredictable bouts of active inflammation and ulceration. Relatively little attention has been paid to the role of antiinflammatory mediators in the pathogenesis of UC, although rodent studies suggest an important role of prostaglandin (PG) D(2) in the resolution of tissue injury and inflammation. The present study was performed to determine if colonic PGD(2) synthesis was altered in patients in remission from UC and if expression of the key enzymes and receptors related to PGD(2) was altered. During routine colon-cancer screening, colonic biopsies were obtained from healthy individuals, some of whom had been in remission from UC, without treatment, for >4 y. UC patients with active disease or in medically induced remission were also biopsied. Only patients with active UC exhibited elevated expression of several proinflammatory cytokines (TNFalpha and IFNgamma) and colonic PGE(2) synthesis. In contrast, colonic PGD(2) synthesis was only elevated ( approximately 3-fold) in the healthy individuals with a prior history of UC. This group also exhibited significantly elevated expression of DP1, the key receptor mediating the antiinflammatory actions of PGD(2). Expression of the synthetic enzymes cyclooxygenase-1, cyclooxygenase-2, and hematopoietic PGD synthase was not altered in the healthy individuals with a prior history of UC. These results show a marked up-regulation of synthesis of an antiinflammatory prostanoid and expression of its receptor, specifically in individuals in long-term remission from UC. This is consistent with animal studies showing the importance of PGD(2) in the induction and maintenance of remission from colitis.

Endogenous and exogenous hydrogen sulfide promotes resolution of colitis in rats

BACKGROUND & AIMS

Hydrogen sulfide (H(2)S) is an endogenous gaseous mediator of mucosal defense with antiinflammatory effects that promote ulcer healing. The effects of H(2)S during the pathogenesis of colitis have not been established. We analyzed the contribution of H(2)S to inflammation and ulceration of the colon in a rat model of colitis.

METHODS

Colitis was induced by intracolonic administration of trinitrobenzene sulfonic acid. The ability of the colon to synthesize H(2)S was studied over the course of the resolution of the colitis. Expression of 2 enzymes involved in the synthesis of H(2)S and the effects of inhibitors of these enzymes were examined. We also examined the effects of H(2)S donors on the resolution of colitis.

RESULTS

The capacity for the colon to produce H(2)S increased markedly over the first days after induction of colitis and then declined toward control levels as the colitis was resolved. Inhibition of colonic H(2)S synthesis markedly exacerbated the colitis, resulting in significant mortality. Inhibition of H(2)S synthesis in healthy rats resulted in inflammation and mucosal injury in the small intestine and colon along with down-regulation of cyclooxygenase-2 messenger RNA expression and prostaglandin synthesis. Intracolonic administration of H(2)S donors significantly reduced the severity of colitis and reduced colonic expression of messenger RNA for the proinflammatory cytokine tumor necrosis factor alpha.

CONCLUSIONS

In rats, H(2)S modulates physiological inflammation and contributes to the resolution of colitis.