Decreased oxidative stress in prehepatic portal hypertensive rat livers following the induction of diabetes

1. Oxidative stress (OS) is a biological entity indicated as being responsible for several pathologies, including diabetes. Diabetes can also be associated with human cirrhosis. Portal hypertension (PH), a major syndrome in cirrhosis, produces hyperdynamic splanchnic circulation and hyperaemia. The present study was designed to investigate the occurrence of OS in prehepatic PH rat livers following the induction of diabetes. 2. Five groups of rats were used: control, sham operated, chronic diabetes (induced with a single dose of streptozotocin at 60 mg/kg, i.p.), prehepatic PH and chronic diabetic plus prehepatic PH. The occurrence of OS was determined in liver homogenates by measuring hydroperoxide-initiated chemiluminescence and the activity of anti-oxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase). 3. Prehepatic PH produced a significant increase in hydroperoxide-initiated chemiluminescence in the liver compared with control and sham-operated rats, whereas the liver in chronic diabetic rats showed no difference. However, chemiluminescence values decreased almost by 50% in the chronic diabetic plus prehepatic PH group. Concomitantly, the activities of the anti-oxidant enzymes in chronic diabetes, prehepatic PH and chronic diabetic plus prehepatic PH groups were decreased (P < 0.05 vs control and sham-operated groups). 4. Livers from the chronic diabetic group did not show any evidence of the occurrence of OS, whereas the prehepatic PH group showed the occurrence of OS. The association of PH and chronic diabetes resulted in a significant decrease in the occurrence of OS, which could be explained by an anti-oxidant response to an OS.

Budesonide enema in pouchitis--a double-blind, double-dummy, controlled trial

BACKGROUND

Pouchitis has been suggested to be a recurrence of ulcerative colitis in a colon-like mucosa. Topical steroids are a valid therapeutic alternative for distal forms of ulcerative colitis.

AIM

To investigate the efficacy and tolerability of budesonide enema in the treatment of pouchitis compared with oral metronidazole.

MATERIALS AND METHODS

Twenty-six patients with an active episode of pouchitis (defined as a pouchitis disease activity index score >or= 7) and no treatment during the previous month were randomized to receive either budesonide enema (2 mg/100 mL at bedtime) plus placebo tablets or oral metronidazole (0.5 g b.d.) plus placebo enema in a prospective, double-blind, double-dummy, 6-week, controlled trial.

RESULTS

Based on the intention-to-treat principle, we detected a significant improvement in disease activity at the end of the first week with both drugs (P < 0.01). After that, improvement was moderated until stabilization at 4 weeks in both treatments. The per protocol analysis showed that both drugs had similar efficacy in terms of disease activity, clinical and endoscopic findings. Fifty-eight per cent and 50% of patients improved (decrease in pouchitis disease activity index >or= 3) with budesonide enema and metronidazole, respectively (odds ratio, 1.4; confidence interval, 0.2-8.9). Adverse effects were observed in 57% of patients given metronidazole and in 25% of patients given budesonide.

CONCLUSIONS

Budesonide enemas are an alternative treatment for active pouchitis, with similar efficacy but better tolerability than oral metronidazole.

Prostanoid production in endothelial and Kupffer liver cells from monocrotaline intoxicated rats

A single dose of monocrotaline, a pyrrolizidine alkaloid, was injected into rats in order to produce 25 (Group I) and 45 (Group II) days later a progressive and so called delayed liver injury. The present study investigated the prostanoid production of Kupffer cells and endothelial cells separated from Monocrotaline and saline (Group III) injected rat livers. Kupffer cells: formation of 6 keto Prostaglandin F1 alpha, the major prostacycline metabolite, gradually decreased in Groups I vs II (P < 0.01) and in both Groups I and II vs Controls (P < 0.01). In addition Prostaglandin F2 alpha showed a significant increase in Groups I and II when compared to Group III, (P < 0.001), and Thromboxane B2 was present in both Groups of Monocrotaline treated animals, while it was not detectable in the control Group III. Endothelial cells: 6 keto Prostaglandin F1 alpha decreased in Groups 1 vs II. This differences was significant when compared, and compared to controls (Group III, P < 0.001). Prostaglandin E2 was detected only in Groups I and II. Prostaglandin F2 alpha and Thromboxane B2 could not be detected in any Group. Ultramicroscopy showed morphological cell damage in nonparenchymal cells in Monocrotaline intoxication in Group II, rats sacrificed 45 days after the injection, while it shows normal features in those treated animals sacrificed 25 days after the injection, as well as in control group.

CONCLUSION

A single Monocrotaline injection produces, 25 and 45 days later, severe and progressive alterations in the prostanoid production in Kupffer and Endothelial cells, while ultramicroscopic alterations was only observed 45 days after the injection of Monocrotaline. A decreased production of vasodilators and the presence of vasoconstrictor prostanoids that can participate in the production of the circulatory derangements enhancing liver injury and portal hypertension were also observed.

Increased mucosal levels of leukotriene B4 in pouchitis: evidence for a persistent inflammatory state

DESIGN AND METHODS

In order to evaluate its possible role in the pathogenesis of pouchitis we measured the release, into the incubation medium of leukotriene B4 from mucosal samples from patients with ileal pouch-anal anastomosis and correlated release with clinical, endoscopic and histological features.

RESULTS

Leukotriene B4 release was significantly elevated in patients with active pouchitis in comparison to those with a normal pouch mucosa (P < 0.007). No overlap was observed between leukotriene B4 levels from patients with active pouchitis samples and those obtained from individuals without pouchitis. Effective treatment of pouchitis was associated with a significant reduction in leukotriene B4 mucosal release to the incubation medium (P < 0.03). However, even in remission, levels of leukotriene B4 release remained significantly increased in these patients in comparison to people who never experienced pouchitis (P < 0.003). A modest correlation was observed between pouchitis disease activity index and leukotriene B4 release (r = 0.596; P < 0.01).

CONCLUSION

These results suggest that the increased production of leukotriene B4 may be implicated in the pathogenesis of pouchitis. The persistence of an increased mucosal release of leukotriene B4 in pouchitis patients during clinical remission suggests the presence of a chronic, ongoing, underlying inflammatory process.

Production of thromboxanes by transformed lymphocytes--effect on heart contractility

We studied the effect of transformed lymphocytes from patients with chronic lymphocytic leukaemia (CLL) and the Raji cell (Raji) on the response of rat isolated atria to sodium arachidonate (AA). In contrast to normal lymphocytes, CLL cells and Raji cells decrease the contractile tension of rat isolated atria. Addition of exogenous AA (1.98 X 10(-6) M) to Raji, further reduced the isometric developed tension. Time of culture of Raji was important, as the negative inotropic effect was greater at 72 h than at 24 h of culture. Living cells were required and cell-free supernatants were inactive. Preincubation of CLL cells or Raji with cyclooxygenase inhibitors (acetyl salycilic acid, indomethacin) or inhibitors of thromboxane (TX) synthesis (imidazole, L-8027) abolished the negative inotropic response suggesting the contribution of TXs. L-8027 also reduced the growth rate of Raji cells, indicating that TXs may play a role in the regulation of cell division. The production of TXs by CLL and Raji cells from both endogenous and exogenous sources provided additional support to this hypothesis and suggested that activation of this metabolic pathway may be related to cell transformation.

The effects of norepinephrine and acetylcholine in the vas deferens from normal and diabetic rats: influence of ouabain and verapamil

In vas deferens from acute and chronic diabetic rats a hypersensitivity to norepinephrine and acetylcholine was observed. The hypersensitivity to norepinephrine was markedly reduced by treatment with ouabain or verapamil. On the contrary, the response to acetylcholine was not modified by ouabain in the same concentration, but was inhibited by verapamil. Under normal conditions, ouabain and verapamil did not modify the stimulatory effect of either norepinephrine and acetylcholine; however increase of extracellular potassium concentrations potentiated the action of norepinephrine. The results suggest that ouabain-sensitive (Na+ + K+)ATPase exists in the rat vas deferens. In diabetic animals, the supersensitivity to norepinephrine is associated with an increase in membrane permeability to calcium ions that could be related to hypersensitivity of the enzyme. Under normal conditions it is possible to mimic the hypersensitivity to norepinephrine through an increase in the extracellular potassium concentration.

Prostaglandins, cyclic AMP production and biological activity of alloimmune thymocytes

The effect of alloimmunized non-adherent thymocytes on the spontaneous activity of the mouse atria was studied. BALB/c anti C3H non-adherent thymocytes induced negative inotropic effect on C3H atria. Cell-free supernatant from non-adherent thymocytes induced the same biological activity. This activity was blunted by the inhibition of non-adherent immune thymocytes' cyclo-oxygenase activity. PGE was present in higher amounts in free-cell supernatant from BALB/c anti C3H thymocytes plus C3H atria than in those from non-immune thymocytes. Intracellular levels of immune thymocytes cAMP are raised in comparison with those of normal thymocytes. It is proposed that alloantigen stimulates non-adherent thymocytes, increasing intracellular levels of cAMP and PGE. Immune thymocytes, release PGE upon recognition of the alloantigens expressed in the atria and this triggers a negative inotropic effect. The increment in immune thymocyte cAMP appears to be associated with the activation of thymocytes cyclo-oxygenase activity by alloimmunization.

Adrenergic stimulation modifies prostaglandin synthesis by rat vas deferens

The effects of norepinephrine on prostaglandin synthesis by isolated rat vas deferens were studied. The organ released prostaglandins (PGs) into the medium, especially PGE1 and also small amounts of PGE2 and PGF-like substances. Norepinephrine increased the amounts of PGE1 and PGE2-like material released into the medium without any change in those of PGF-like material. The effect of norepinephrine was inhibited by phenoxybenzamine and propranolol, but not by yohimbine. Inasmuch as mepacrine and corticosterone antagonized the response to norepinephrine on PG release the possible involvement of the adrenergic agonist on the activity of phospholipase A2 is suggested. It is concluded that norepinephrine elicits PGs-synthesis in rat vas deferens via an adrenoceptor stimulation. The adrenoceptor involved in this reaction, is probably postsynaptic (alpha 1).

The positive inotropic effect of sodium arachidonate on auricles from diabetic rats

Contractile responses to exogenous sodium arachidonate (NaA) were studied in auricles from normal and acutely diabetic (streptozotocin-treated) rats. NaA induced a concentration-dependent positive inotropic effect in atria from normal and diabetic rats but the magnitude of the contractile influence of the fatty acid was different in both types of auricles, i.e. diabetic atria had a greater responsiveness to NaA than normal preparations. Blockers of arachidonic acid (AA) metabolism via cyclo-oxygenase (indomethacin and acetylsalicylic acid), abolished the stimulatory influence of NaA in normal and in diabetic auricles. Moreover, incubation with tranylcipromine, a prostacyclin synthetase inhibitor, reduced the inotropic effect of NaA in normal atria, but failed to modify it in the diabetic atria. On the other hand, inhibitors of thromboxane (TX) synthetase (imidazole and L-8027) diminished the effect of NaA in diabetic preparations without altering the contractile responses in the controls. In the presence of lipoxygenase blocking agents (nordihydroguaiaretic acid and dithizone), the influence of NaA was reduced at normal values only in the atria from diabetic rats. Both atrial preparations (normal and diabetic) converted ([1-14C]arachidonic acid (AA) into PGI2 (assessed as 6-oxo-PGF1 alpha) and TXB2. Moreover, normal atria generated more PGI2 than TXB2 whereas TXB2 production was greater than that of PGI2 in diabetic atria. The foregoing results suggest that in non-diabetic atria the effect of exogenous NaA may be attributed to metabolites generated by the sequential action of cyclo-oxygenase and prostacyclin synthetase. On the other hand, the contractile action of exogenous NaA in diabetic atria may be ascribed to thromboxanes and lipoxygenase(s) metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)

Alloimmunization-induced changes in thymocytes' prostaglandin levels: a signal for the induction of biological activity

The effect of BALB/c anti C3H non-adherent thymocytes on the spontaneous activity of isolated C3H mouse atria was studied. Immune non-adherent thymocytes alone induced negative inotropic action, while macrophages alone did not have any effect. The same kind of collaborative effect between both cells is described. Cell-free supernatants obtained from non-adherent immune cells incubated with C3H myocardium induced the same biological activity than immune non-adherent thymocytes indicating that a soluble factor is involved. Inhibition of non-adherent thymocytes' cyclo-oxygenase activity prevented the negative inotropic effect of immune cells or cell-free supernatants. In contrast, when the inhibitors were applied upon myocardium did not modify the response. Supernatants from immune thymocytes plus myocardium, release higher amount of PGE series than those from non-immune thymocytes. It is proposed that non-adherent thymocytes are able to synthesize and release PGE series upon recognition of alloantigens expressed by atria cells; which in turn triggers the negative inotropic effect.

Hypersensitivity to norepinephrine in vasa deferentia from diabetic rats. Possible participation of metabolic products of arachidonic acid

Contractile responses to norepinephrine of the vas deferens isolated from normal and diabetic rats as well as tissue radio-conversion of exogenous arachidonic acid, were studied. Vasa deferentia from rats with acute streptozotocin-induced diabetes showed hypersensitivity to exogenous norepinephrine (NE). This increased contractile response was associated with the interaction of the agonist with alpha adrenoceptors. Inhibitors of cyclooxygenase increased and inhibitors of lipoxygenase(s) abolished the enhanced response to NE of diabetic vas deferens. Vasa deferentia from both normal and diabetic rats, converted (1-14C)-arachidonic acid (AA) into PGF, PGE, PGD and thromboxane (TX) B2, but the % of AA metabolites formed was significantly higher in the diabetic than in the normal condition. Moreover, the predominant prostanoid generated by tissue preparations from diabetic animals was PGD2. Taken together the present experimental findings indicate that preparations from rats with acute streptozotocin-induced diabetes have an augmented reactivity towards NE, which appeared associated with changes in metabolites of AA generated via cyclooxygenase and lipoxygenase catalized pathways.

Alpha adrenergic stimulation modified prostaglandins release in vas deferens

Methoxamine enhanced contractions of mouse vasa deferentia through alpha adrenoceptor stimulation. Additionally, the generation of PGF-like material by the tissue was increased by methoxamine, whereas that of PGE-like material was decreased. The effects of methoxamine on prostaglandin output (stimulation and depression) were antagonized by yohimbine and phenoxybenzamine. Moreover, the stimulating influence of methoxamine on the contractile activity of the preparations was attenuated by the prostaglandin synthesis inhibitors indomethacin and acetylsalicylic acid. The results suggest that methoxamine is able to modify prostaglandin synthesis and output in mouse vasa deferentia, probably through an alpha adrenergic mediated mechanism coupled to the prostaglandin synthesizing system. The fact that indomethacin and acetylsalicylic acid blocked alpha stimulatory responses to methoxamine, suggest a modulatory role for endogenous prostaglandins. Since methoxamine increased PGF levels, this prostaglandin might potentiate the contractile influence of methoxamine.

Contractile activity of the isolated rat vas deferens and release of prostaglandin E and F-like substances. Influences of acetylcholine and inhibitors of cyclo-oxygenase and phospholipase A2

The isolated epididymal portion of the rat vas deferens releases spontaneously and in response to acetylcholine prostaglandin-like material into the suspending solution. The output of prostaglandin E2 and F2 alpha-like substances, evoked by the cholinergic agonist, was significantly higher than the basal generation. Atropine, but not hexamethonium, markedly reduced the release elicited by acetylcholine. In addition corticosterone, quinacrine and verapamil also decreased significantly the acetylcholine-induced prostaglandin output. Inasmuch as quinacrine and corticosterone antagonized the response to acetylcholine the possible involvement of the cholinergic agonist on the activity of phospholipase A2, is suggested. Furthermore, the role of prostaglandins in relation to the action of acetylcholine on the contractile activity of the epididymal portion of isolated vas deferens, was also explored. It is concluded that these autacoids modulate the contractions evoked by acetylcholine.