Misoprostol but not antacid prevents endotoxin-induced gastric mucosal injury: role of tumor necrosis factor-alpha

Misoprostol Inhibits Lipopolysaccharide-Induced Pro-inflammatory Cytokine Production by Equine Leukocytes

Pro-inflammatory cytokines including tumor necrosis factor α (TNFα), IL-1β, IL-6, and IL-8 are potent immune mediators that exacerbate multiple equine diseases such as sepsis and laminitis. Unfortunately, safe and effective cytokine-targeting therapies are lacking in horses; therefore, novel mechanisms of inhibiting cytokine production are critically needed. One potential mechanism for inhibiting cytokine synthesis is elevation of intracellular cyclic AMP (cAMP). In human leukocytes, intracellular cAMP production is induced by activation of E-prostanoid (EP) receptors 2 and 4. These receptors can be targeted by the EP2/4 agonist and prostaglandin E1 analog, misoprostol. Misoprostol is currently used as a gastroprotectant in horses but has not been evaluated as a cytokine-targeting therapeutic. Thus, we hypothesized that misoprostol treatment would inhibit pro-inflammatory cytokine production by lipopolysaccharide (LPS)-stimulated equine leukocytes in an in vitro inflammation model. To test this hypothesis, equine leukocyte-rich plasma (LRP) was collected from 12 healthy adult horses and used to model LPS-mediated inflammatory signaling. LRP was treated with varying concentrations of misoprostol either before (pretreated) or following (posttreated) LPS stimulation. LRP supernatants were assayed for 23 cytokines using an equine-specific multiplex bead immunoassay. Leukocytes were isolated from LRP, and leukocyte mRNA levels of four important cytokines were evaluated via RT-PCR. Statistical differences between treatments were determined using one-way RM ANOVA (Holm-Sidak post hoc testing) or Friedman's RM ANOVA on Ranks (SNK post hoc testing), where appropriate (p < 0.05, n = 3-6 horses). These studies revealed that misoprostol pre- and posttreatment inhibited LPS-induced TNFα and IL-6 protein production in equine leukocytes but had no effect on IL-8 protein. Interestingly, misoprostol pretreatment enhanced IL-1β protein synthesis following 6 h of LPS stimulation, while misoprostol posttreatment inhibited IL-1β protein production after 24 h of LPS stimulation. At the mRNA level, misoprostol pre- and posttreatment inhibited LPS-induced TNFα, IL-1β, and IL-6 mRNA production but did not affect IL-8 mRNA. These results indicate that misoprostol exerts anti-inflammatory effects on equine leukocytes when applied before or after a pro-inflammatory stimulus. However, the effects we observed were cytokine-specific and sometimes differed at the mRNA and protein levels. Further studies are warranted to establish the inhibitory effects of misoprostol on equine cytokine production in vivo.

A randomized, double-blind, placebo-controlled trial of misoprostol for oral mucositis secondary to high-dose chemotherapy

PURPOSE

Misoprostol, a synthetic analog of prostaglandin E1, has anti-inflammatory and mucosa-protecting properties. The objective of this study was to evaluate the efficacy of misoprostol oral rinse in reducing the severity of oral mucosal injury caused by high-dose chemotherapy.

METHODS

The study used a randomized, double-blind, placebo-controlled, parallel-group design. Oncology patients receiving myeloablative high-dose chemotherapy, in preparation for a hematopoietic stem cell transplant, were randomized to misoprostol or placebo rinse. The primary outcome measure was the severity of oral mucositis, measured using the modified Oral Mucositis Index. Additional outcome measures included the severity of mouth pain (measured using a Visual Analog Scale and the Pain Affect Faces Scale), duration of hospital stay, and days on total parenteral nutrition.

RESULTS

This study was originally planned to accrue 160 subjects but was terminated early due to revised sponsor research priorities. The intent-to-treat population consisted of 22 subjects randomized to misoprostol rinse and 26 subjects randomized to placebo rinse. There was no significant difference between the two groups in mucositis or pain severity. In both groups, duration of hospital stay was approximately 19 days, and number of days on total parenteral nutrition was 17-18 days. There were no serious adverse events attributable to misoprostol rinse.

CONCLUSIONS

Although this study did not find a beneficial effect of a misoprostol rinse in mucositis secondary to high-dose chemotherapy, the small sample size limits the strength of this conclusion. Given the proposed importance of the prostaglandin pathway in the pathogenesis of oral mucositis, additional studies are warranted.

A randomized controlled trial of misoprostol monotherapy for canine atopic dermatitis: effects on dermal cellularity and cutaneous tumour necrosis factor-alpha

In this blinded randomized placebo-controlled trial, 20 dogs with atopic dermatitis (AD) were given placebo (8 dogs) or misoprostol (12 dogs) at 5 micro g kg-1, orally, three times daily for 3 weeks. Administration of the active drug, but not of placebo, led to a significant decrease in lesional and pruritus scores. The median reduction from baseline of both scores was approximately 30%. Misoprostol therapy did not lead to decreases of dermal cell counts or skin tumour necrosis factor (TNF)alpha mRNA copy numbers that were significantly different from those of placebo. Skin TNFalpha protein production, assessed using indirect immunofluorescence, decreased or remained unchanged in dogs receiving misoprostol. In contrast, post treatment TNFalpha fluorescence scores were higher in all but two dogs given placebo. The changes from baseline of TNFalpha fluorescence scores did not correlate significantly with those of lesional or pruritus indices. These observations confirm the modest efficacy of misoprostol for treatment of canine AD and suggest that its mild anti-allergic effects are not associated with either inhibition of inflammatory cell emigration or TNFalpha production.

Misoprostol therapeutics revisited

Misoprostol, a prostaglandin E1 analog, is a racemate of four stereoisomers. On administration it rapidly de-esterifies to its active form, misoprostolic acid. Misoprostolic acid is 85% albumin bound and has a half-life of approximately 30 minutes. It is excreted in urine as inactive metabolites. No significant drug interactions have been reported. Besides its gastrointestinal protective and uterotonic activities, misoprostol regulates various immunologic cascades. It inhibits platelet-activating factor and leukocyte adherence, and modulates adhesion molecule expression. It protects against gut irradiation injury, experimental gastric cancer, enteropathy, and constipation. It improves nutrient absorption in cystic fibrosis. Misoprostol has utility in acetaminophen and ethanol hepatotoxicity, hepatitis, and fibrosis. It is effective in asthmatics and aspirin-sensitive asthmatic and allergic patients. It lowers cholesterol and severity of peripheral vascular diseases, prolongs survival of cardiac and kidney transplantation, synergizes cyclosporine, and protects against cyclosporine-induced renal damage. It works against drug-induced renal damage, interstitial cystitis, lupus nephritis, and hepatorenal syndrome. It is useful in periodontal disease and dental repair. Misoprostol enhances glycosoaminoglycan synthesis in cartilage after injury. It prevents ultraviolet-induced cataracts and reduces intraocular pressure in glaucoma and ocular hypertension. It synergizes antiinflammatory and analgesic effects of diclofenac or colchicine and has been administered to treat trigeminal neuralgic pain. It reduces chemotherapy-induced hair loss and recovery time from burn injury, and is effective in treating sepsis, multiple sclerosis, and pancreatitis.

Idiopathic esophageal ulceration in acquired immunodeficiency syndrome: successful treatment with misoprostol and viscous lidocaine

OBJECTIVE

Esophageal ulceration is a common and important cause of morbidity in patients with acquired immunodeficiency syndrome (AIDS). After known causes are excluded, a subgroup remains with unexplained esophageal ulceration, known as idiopathic esophageal ulceration (IEU). The current therapy of IEU includes corticosteroids or, less frequently, thalidomide, although no placebo-controlled trials have been reported. The aim of this retrospective study was to determine the outcome of treating IEU with misoprostol and viscous lidocaine.

METHODS

A retrospective review of esophageal ulceration in AIDS identified seven subjects with IEU at our institution. IEU in these subjects was treated successfully with misoprostol, 200 microg, crushed and suspended in 2% viscous lidocaine, 15 ml, given orally a.c. and h.s. for 4 wk.

RESULTS

All patients reported symptomatic improvement within 2-3 days and complete resolution of their symptoms within 15 days. Healing of esophageal ulcerations was confirmed in five of seven subjects at a repeat endoscopy 8-12 wk later.

CONCLUSIONS

Misoprostol, an antiulcer drug, has GI cytoprotective properties, and viscous lidocaine, a topical anesthetic, coats mucosal surfaces. We speculate that misoprostol when delivered topically is 3-6 times more effective than when delivered systemically. Considering the rapid resolution of symptoms, healing of ulcers, and lack of side effects, we believe that misoprostol crushed and suspended in viscous lidocaine should be considered for further evaluation in prospective, placebo-controlled trials of IEU.

The prostaglandin analogs, misoprostol and SC-46275, potently inhibit cytokine release from activated human monocytes

Inflammatory mediator release is one of the body's responses to tissue injury and inflammation. These mediators, such as interleukin-1 beta (I1-1 beta), tumor necrosis factor (TNF-alpha), and products of arachidonic acid metabolism, are themselves proinflammatory. Purified human monocytes stimulated in vitro with E. coli-derived lipopolysaccharide (LPS) will release these key cytokines along with various other eicosanoid mediators. Monocytes incubated with LPS and the prostaglandin E-1 analog, misoprostol, released significantly lower levels of cytokines compared to monocytes incubated with LPS alone. Eicosanoid release was also affected by misoprostol. SC-46275, a more potent mucosal protective PGE1 analog, also altered the release of cytokines and eicosanoids from human monocytes. However SC-46275 inhibited I1-1 beta release with an IC50 value of 9 microM compared to 75 microM for misoprostol. SC-46275 and misoprostol both inhibited TNF-alpha release. These data suggest there is a potential immunomodulatory role for prostaglandin analogs in the therapeutic treatment of inflammatory diseases such as ulcerative colitis, Crohn's disease, and autoimmune inflammatory diseases of the central nervous system.

Misoprostol inhibits gastric mucosal release of endogenous prostaglandin E2 and thromboxane B2 in healthy volunteers

Prostaglandin analogues of the E-series theoretically offer the ideal antiulcer drugs. Peptic ulcer healing with prostaglandin analogues is, however, no better than would be predicted from their ability to inhibit gastric acid secretion and they are less effective than histamine H2 receptor antagonists in preventing ulcer relapse. It could be that prostaglandin analogues inhibit gastric mucosal synthesis or release of endogenous eicosanoids, thereby abrogating their own effects. This study, therefore, examined how a single therapeutic dose (200 micrograms) of misoprostol, a synthetic analogue of prostaglandin E1, influences gastric mucosal release of endogenous prostaglandin E2 (PGE2), thromboxane B2 (TXB2), and chemotactic leukotriene B4 (LTB4) during basal conditions and in response to gastric luminal acidification (0.1 M HCl; 5 ml/min for 10 minutes). Nine healthy volunteers were studied in a single blind, cross over design. In each subject misoprostol or placebo was instilled in randomised order into the stomach, which was subsequently perfused with isotonic mannitol. Misoprostol significantly decreased basal as well as acid stimulated output of PGE2 and TXB2, without affecting output of LTB4. These data show that misoprostol inhibits gastric mucosal synthesis of prostanoids. Decreased concentrations, or even a changed profile, of native eicosanoids modulating the release of inflammatory mediators from immune cells might explain why prostaglandin analogues have a comparatively poor clinical performance in ulcer healing and prevention.

Prostaglandins inhibit inflammatory mediator release from rat mast cells

BACKGROUND

Mast cells have been implicated in the pathogenesis of gastric ulceration. It is possible that prostaglandins exert cytoprotective effects by inhibiting the release of proulcerogenic mediators from mast cells.

METHODS

The effects of three prostaglandins on the release of platelet-activating factor, tumor necrosis factor, and histamine from rat mast cells (peritoneal and intestinal mucosal) activated with calcium ionophore or antigen were assessed.

RESULTS

Upon stimulation with either agonist, intestinal mucosal and peritoneal mast cells released significant quantities of platelet-activating factor. Preincubation for 5 minutes with misoprostol, prostaglandin (PG)E2, 16,16-dimethyl PGE2, ketotifen, or PF-5901 concentration-dependently reduced ionophore-stimulated platelet-activating factor release; significant effects were observed with picomolar to nanomolar concentrations of the prostaglandins and micromolar concentrations of the other compounds. Tumor necrosis factor release from peritoneal and mucosal mast cells was also significantly inhibited by the prostaglandins in picomolar to nanomolar concentrations. Misoprostol and PGE2 at concentrations of 5-50 nmol/L significantly inhibited histamine release from peritoneal mast cells stimulated with ionophore but did not affect histamine release stimulated by antigen.

CONCLUSIONS

These results show potent inhibitory effects of prostaglandins on the release of pro-ulcerogenic inflammatory mediators from mast cells. Such effects may contribute to the protective and anti-inflammatory effects of prostaglandins in the gastrointestinal tract and elsewhere.

Gastric interleukin-8 and IgA IL-8 autoantibodies in Helicobacter pylori infection

Gastric infection with Helicobacter pylori is frequently characterized by neutrophil infiltration. The production of the neutrophil-activating peptide (NAP-1/IL-8) and mucosal IgA autoantibodies to IL-8 by human antral biopsies have been examined during short-term in vitro culture. Detectable IL-8 was secreted by 84% of H. pylori-negative patients with normal antral mucosa (range < 0.07-61.5 ng/mg biopsy protein, n = 19). Concentrations in 4 patients with reactive gastritis and 10 with inactive gastritis were not significantly different from subjects with normal mucosa. In H. pylori-positive patients with active gastritis and neutrophil infiltration into the epithelium (n = 17) IL-8 secretion was significantly increased relative to subjects with normal mucosa (P < 0.0001), inactive gastritis (P < 0.001) and reactive gastritis (P < 0.01). IL-8 concentrations in active gastritis were significantly correlated with the extent of epithelial surface degeneration (r = 0.64). IgA autoantibodies were present in 19 patients (13 active, 4 inactive gastritis) and concentrations were significantly correlated with IL-8 production (P < 0.001). Gastric synthesis of IL-8 is likely to be an important factor in regulating mucosal neutrophil infiltration and activation in patients with H. pylori infection. The local production of IgA antibodies to IL-8 may represent a down-regulatory response of the host to limit mucosal damage associated with a chronic bacterial infection.

The degree of bacterial translocation is a determinant factor for mortality after burn injury and is improved by prostaglandin analogs

Bacterial translocation and related mortality rates were examined in previously transfused BALB/c mice that were gavaged with 14C radioisotope-labeled Escherichia coli before inflicting a 20% full-thickness flame burn. Radionuclide counts were measured in blood obtained by retro-orbital puncture 4 hours postburn, and survival was recorded for 10 days. Radionuclide counts in the blood correlated well with both radionuclide counts and numbers of viable bacterial in the tissues. Survivors had significantly less bacterial translocation as evidenced by blood radionuclide counts compared with nonsurvivors, and there was a significant inverse correlation between the degree of translocation and the length of survival. In the next experiment, the prostaglandin E (PGE) analogs misoprostol, enisoprost, or 16,16-dimethyl PGE2 were administered to transfused animals for 3 days before burn. Prostaglandin E analogs significantly reduced bacterial translocation as measured by blood radionuclide counts 4 hours postburn and improved survival. The data demonstrate that the intensity of bacterial translocation after burn injury is significantly associated with subsequent death. Improvement of survival by PGE analogs is associated with decreased bacterial translocation.