Differential inhibitory potencies of non-steroidal antiinflammatory drugs on smooth muscle prostanoid synthesis

The knockout effect of low doses of gamma radiation on hepatotoxicity induced byEchis Coloratussnake venom in rats.. [DOI: 10.1101/705251]

Echis Coloratusis the most medically important viper in Egypt causing several pathological effects leading to death. Gamma radiation has been used as a venom detoxifying tool in order to extend the lifespan of the immunized animals used in antivenin production process. Thus, the aim of this study is to assess the effects of increasing doses of gamma radiation onEchis Coloratusin vivo through biochemical and histological studies. The results revealed a significant increase in the levels of AST, ALT, ALP and glucose of sera collected from the rats injected with nativeEchis Coloratusvenom compared with the non-envenomed group. On the other hand, biochemical parameters of sera of rats administrated with either 1.5 kGy or 3 kGy irradiated venom were significantly decrease compared with the native venom envenomed group at 2h, 4h and 24h post envenomation. In addition, these results were confirmed by histological studies of rats’ livers. Correspondingly, the sublethal dose injection of nativeEchis Coloratusvenom induced significant alterations in the histological architecture of liver after 2, 4 and 24 h of injection. Concurrently, the administration of both 1.5 kGy and 3 kGy gamma irradiated venom showed fewer histological alterations compared with the native group. In conclusion, the present findings support the idea of using gamma radiation as an effective venom detoxification tool.

Prostaglandin modulation of venoconstriction to physiological stress in normals and heart failure patients

Prostaglandins released from blood vessels modulate vascular tone, and inhibition of their production during exogenous infusions of catecholamines causes increased venoconstriction. To determine the influence of prostaglandin production on venoconstriction during physiological stimuli known to cause sympathetic activation, and to assess its importance in chronic heart failure (CHF), we studied 11 normal subjects (62 +/- 4 yr) and 14 patients with CHF (64 +/- 2 yr, left ventricular ejection fraction 23 +/- 1%, New York Heart Association classes II and III) (means +/- SE). Dorsal hand vein distension was measured during mental arithmetic (MA), cold pressor test (CPT), and lower body negative pressure (LBNP; -10 and -40 mmHg), with saline infusion in one hand and local indomethacin (cyclooxygenase inhibitor) infusion (3 microg/min) in the other. Acetylcholine (0.01-1 nmol/min) dilated veins preconstricted with PGF(2alpha) in normals but, consistent with endothelial dysfunction, barely did so in CHF patients (P = 0.001). Nonendothelial venodilation to sodium nitroprusside (0.3-10 nmol/min) was not different between normals and CHF patients. Resting venous norepinephrine levels were higher in CHF patients (2,812 +/- 420 pmol/l) than normals (1,418 +/- 145 pmol/l, P = 0.007). In normals, indomethacin caused increased venoconstriction to MA (from 4.9 +/- 1.5 to 19.2 +/- 4.5%, P = 0.022) and CPT (from 2.9 +/- 3.8 to 17.6 +/- 4.2%, P = 0.007). In CHF, indomethacin caused increased venoconstriction to MA (from 6.6 +/- 3.9% to 19.0 +/- 4.5%, P = 0.014), CPT (from 9.6 +/- 2.1% to 20.1 +/- 3.7%, P = 0.001), and -40 mmHg LBNP (from 10.7 +/- 3.0% to 23.2 +/- 3.8%, P = 0.041). Control responses for all tests were not different between normals and CHF patients. The effects of indomethacin on venoconstriction to MA and CPT were not different between normals and CHF patients, but venoconstriction to -40 mmHg LBNP was accentuated in CHF patients (P = 0.036). Inhibition of prostaglandins by indomethacin significantly enhances hand vein constriction to physiological stimuli in both normals and CHF patients, although a differential effect exists for LBNP.

Response to isoprenaline of rabbit detrusor muscle following exposure to 5, 8, 11, 14 eicosatetraynoic acid. Role of prostanoids on beta-adrenergic-evoked response

1. Incubation with indomethacin or ibuprofen causes a fall in basal tone and inhibits isoprenaline-evoked response in rabbit detrusor muscle strips. To ascertain whether this is due to cyclo-oxygenase inhibition, we investigated the influence on beta-adrenoceptor response of 5, 8, 11, 14 eicosatetraynoic acid (ETYA) which, unlike nonsteroidal anti-inflammatory drugs, has no action in vitro other than cyclo-oxygenase inhibition. 2. Incubation of detrusor strips with ETYA (7 or 14 microM) for 60 min significantly reduced tissue response to isoprenaline by an extent similar to that induced by indomethacin, but only slightly affected basal tone. 3. In tissues preincubated with indomethacin, the addition of PGE2 or PGE1 to restore basal tone, completely re-established isoprenaline-evoked responses. 4. Our findings in rabbit detrusor strips show that inhibition of cyclo-oxygenase and of prostanoid production is the main mechanism involved in lowered beta-adrenoceptor evoked response. 5. In addition, these findings strengthen the conviction that ibuprofen and indomethacin act largely through mechanisms other than inhibition of prostanoid production.

Endothelial calcium-calmodulin dependent nitric oxide synthase in the in vitro vascular hyporeactivity of portal hypertensive rats

BACKGROUND/AIMS

Increased nitric oxide production has been implicated in impaired vascular responsiveness to vasoconstrictors in portal hypertension. However, there is no firm evidence concerning the involved nitric oxide synthase isoform. The present study investigated the possible contribution of one nitric oxide synthase isoform, the endothelial constitutive Ca2+-calmodulin dependent, in the overproduction of nitric oxide in portal hypertension.

METHODS

Vascular responses to norepinephrine and acetylcholine were evaluated in isolated thoracic aortic rings from normal and portal vein stenosed rats.

RESULTS

An impaired concentration-dependent contraction to norepinephrine was observed in intact rings from portal hypertensive rats compared to controls. The hyporeactivity to norepinephrine was reversed after endothelium denudation, the inhibition of nitric oxide synthase with L-NOARG or the inhibition of calmodulin with W-7, but not after pre-incubation with indomethacin. Stimulation of intact rings with norepinephrine after the inhibition of calmodulin with calmidazolium was followed by a decreased vascular response in vessels from normal rats but not in those from portal hypertensive rats. Stimulation of intact rings with norepinephrine in a Ca2+-free medium was followed by a decreased vascular response in vessels from both portal hypertensive and normal rats. No difference in vasoconstrictive responses was observed between the two groups after calmidazolium or in a Ca2+-free medium. Relaxation induced by acetylcholine in norepinephrine-precontracted rings was more marked in rings from portal hypertensive rats than in controls. No differences in the vasodilator responses were observed after relaxations had been inhibited by the removal of the endothelium, pre-incubation with L-NOARG, indomethacin, W-7 or calmidazolium and in a Ca2+-free medium.

CONCLUSIONS

This study demonstrates the involvement of the endothelial constitutive Ca2+-calmodulin dependent nitric oxide synthase isoform in the overproduction of nitric oxide in portal hypertension.

On radiation damage to normal tissues and its treatment. II. Anti-inflammatory drugs

In addition to transiently inhibiting cell cycle progression and sterilizing those cells capable of proliferation, irradiation disturbs the homeostasis effected by endogenous mediators of intercellular communication (humoral component of tissue response to radiation). Changes in the mediator levels may modulate radiation effects either by assisting a return to normality (e.g., through a rise in H-type cell lineage-specific growth factors) or by aggravating the damage. The latter mode is illustrated with reports on changes in eicosanoid levels after irradiation and on results of empirical treatment of radiation injuries with anti-inflammatory drugs. Prodromal, acute and chronic effects of radiation are accompanied by excessive production of eicosanoids (prostaglandins, prostacyclin, thromboxanes and leukotrienes). These endogenous mediators of inflammatory reactions may be responsible for the vasodilatation, vasoconstriction, increased microvascular permeability, thrombosis and chemotaxis observed after radiation exposure. Glucocorticoids inhibit eicosanoid synthesis primarily by interfering with phospholipase A2 whilst non-steroidal anti-inflammatory drugs prevent prostaglandin/thromboxane synthesis by inhibiting cyclooxygenase. When administered after irradiation on empirical grounds, drugs belonging to both groups tend to attenuate a range of prodromal, acute and chronic effects of radiation in man and animals. Taken together, these two sets of observations are highly suggestive of a contribution of humoral factors to the adverse responses of normal tissues and organs to radiation. A full account of radiation damage should therefore consist of complementary descriptions of cellular and humoral events. Further studies on anti-inflammatory drug treatment of radiation damage to normal organs are justified and desirable.

A comparison of indomethacin with ibuprofen on gastrointestinal mucosal integrity in conventional and germ-free rats

The effects of indomethacin and ibuprofen on gastrointestinal mucosal integrity were studied in conventional and germ-free rats. Only ibuprofen induced significant gastric erosion formation in both conventional and germ-free animals, demonstrating that the presence of micro-organisms is not required in this form of damage. Both indomethacin and ibuprofen caused significant intestinal damage and blood loss in germ-free animals. However, in the conventional counterparts, damage due to indomethacin was enhanced whereas that induced by ibuprofen was not. The results from the present work would suggest that non-steroidal anti-inflammatory drugs such as indomethacin, which are secreted largely in the bile, unlike ibuprofen, may act in concert with bacteria and the constituents of bile to induce, in part, intestinal damage and blood loss.

Attenuated responses to endothelin-1, KCl and CaCl2, but not noradrenaline, of aortae from rats with streptozotocin-induced diabetes mellitus

1. This study investigated the responsiveness to vasoconstrictor agents (including endothelin-1, ET-1) of aortic rings from rats with two-week streptozotocin (STZ, 60 mg kg-1, i.v.)-induced diabetes and vehicle-treated control rats. The basal tension was 10 g, which was estimated to be more physiological than the tension of 1-2 g that has been previously used for most studies of aortic rings from diabetic rats. 2. Maximum responses to ET-1 (0.13-18 nM), KCl (2-20 mM) or CaCl2 (10 microM-10 mM) were reduced in aortae from STZ-treated rats compared to those from control rats. Such reductions were still evident after removal of the endothelium. 3. Responses to noradrenaline (NA, 0.1 nM-26 microM) of aortae from STZ-treated rats were not significantly different from responses of aortae of control rats. 4. Removal of endothelium resulted in a significant reduction in the EC50 values for NA of rings from both STZ-treated rats (6.90 +/- 0.13 and 8.17 +/- 0.35 (-log M) with and without endothelium, respectively, n = 5) and control rats (6.90 +/- 0.15 and 8.37 +/- 0.44 (-log M) with and without endothelium, respectively, n = 5). 5. In calcium-free medium (with 1 mM EGTA), responses to NA and ET-1 were reduced compared with those in normal Krebs solution and maximum responses were less in rings from STZ-treated compared with control rats. 6. Indomethacin (5 microM) did not prevent the reduced maximum responsiveness to ET-1 in rings from STZ-treated rats compared with those from controls.7. This study indicates that changes in vascular responsiveness to ET-1, KCI and CaCl2 (but not NA) occur in aortae of two-week STZ-treated rats. The endothelium does not appear to play a major role in mediating changes in responsiveness to ET-1.