A. Pistelli

Nitric Oxide: A Regulatory Mediator of Mast Cell Reactivity

Rat serosal mast cells were tested for their ability to generate a nitric oxide (NO)-like factor by two bioassay systems: inhibition of platelet aggregation and stimulation of mast cell guanylate cyclase. The relationship between histamine release and NO-like activity from these cells was also investigated. Incubation with human washed platelets of rat serosal mast cells treated with indomethacin resulted in an inhibition of thrombin-induced platelet aggregation proportional to the number of cells.

Rat mast cells synthesize a nitric oxide like-factor which modulates the release of histamine

Rat serosal mast cells were evaluated for their capacity to generate a nitric oxide-like factor by two bioassays: inhibition of platelet aggregation and stimulation of mast cell guanylate cyclase. Incubation of mast cells with human washed platelets, both treated with indomethacin, inhibited thrombin-induced platelet aggregation which was potentiated by superoxide dismutase and reversed by oxyhaemoglobin. When mast cells alone were stirred at 1000 rpm, a time dependent increase in the levels of their cGMP but not cAMP was observed. Preincubation of mast cells with NG-monomethyl-l-arginine significantly enhanced E. coli lipopolysaccharide-evoked histamine release. Our results show that mast cell histamine release can be modulated by an intrinsically generated nitric oxide-like factor.

Pregnancy Outcome After Methotrexate Treatment for Rheumatic Disease Prior to or During Early Pregnancy: A Prospective Multicenter Cohort Study

High‐dose methotrexate (MTX) exposure during pregnancy is associated with embryopathy. The teratogenic potential of MTX at dosages typically used in the treatment of rheumatic diseases remains uncertain. The aim of this study was to evaluate the risk of spontaneous abortion, major birth defects, elective termination of pregnancy, shortened gestational age at delivery, and reduced birth weight in women exposed to MTX.

The effect of nitric oxide generators on ischemia reperfusion injury and histamine release in isolated perfused guinea-pig heart.

Experiments were carried out to provide evidence of the effect ofl-arginine (l-Arg), its analogue NG-monomethyl-l-arginine (MeArg) and of some nitrovasodilators (sodium nitroprusside, NaNP; 3-morpholino-sydnonimine, SIN-1) which spontaneously release nitric oxide (NO) on ischemia-reperfusion injury, histamine release and mast cell degranulation, occurring after multiple ligature and release of the left anterior descending (LAD) coronary artery in isolated perfused guinea-pig hearts. The reopening of the LAD coronary artery leads to a release of histamine related to a decrease in microdensitometry of cardiac mast cells and to calcium overload. The perfusion of the heart with NO-donors significantly reduces either the release of histamine, the loss of mast cell metachromasia and the overload of calcium. These effects were potentiated by SOD. The results suggest that the endogenous formation of NO and molecules able to generate NO have a role in the prevention of post-ischemic tissue injury.

Pregnancy outcomes following gabapentin use: Results of a prospective comparative cohort study

Objectives: Our objectives were to 1) determine whether first-trimester use of gabapentin is associated with an increased risk for major malformations; 2) examine rates of spontaneous abortions, therapeutic abortions, stillbirths, mean birth weight and gestational age at delivery; and 3) examine rates of poor neonatal adaptation syndrome following late pregnancy exposure. Methods: The study design was prospective. Women were included who initially contacted the services between 5 and 8 weeks with a comparison group of women exposed to nonteratogens, collected in a similar manner. Results: We have data on 223 pregnancy outcomes exposed to gabapentin and 223 unexposed pregnancies. The rates of major malformations were similar in both groups (p = 0.845). There was a higher rate of preterm births (p = 0.019) and low birth weight <2,500 g (p = 0.033) in the gabapentin group. Among infants who were exposed to gabapentin up until delivery, 23 of 61 (38%) were admitted to either the neonatal intensive care unit or special care nursery for observation and/or treatment, vs 6 of 201 (2.9%) live births in the comparison group (p < 0.001). There were 2 cases of possible poor neonatal adaptation syndrome in neonates exposed to gabapentin close to delivery, compared with none in the comparison group, although it must be noted that these infants were concomitantly exposed to other psychotropic drugs. Among the women who took gabapentin, the major indications were pain (n = 90; 43%) and epilepsy (n = 71; 34%); the remainder were for other indications, mostly psychiatric. Conclusion: Our results suggest that although this sample size is not large enough to make any definitive conclusions, and there was no comparator group treated with other antiepileptic drugs, gabapentin use in pregnancy does not appear to increase the risk for major malformations. This finding and the increased risk for low birth weight and preterm birth require further investigation.

Histamine release from rat mast cells induced by metabolic activation of polyunsaturated fatty acids into free radicals

Polyunsaturated fatty acids (PUFA: arachidonic and linoleic acid) release histamine from isolated purified rat serosal mast cells only in the presence of oxidizing systems such as phenobarbital-induced rat liver microsomes, prostaglandin-H-synthetase (PHS) or soybean lipoxygenase. The release of mast cell histamine by activated PUFA has a long time-course and the electron microscopical features are consistent with an exocytotic secretion in the case of arachidonic acid and cell lysis in the case of linoleic acid. The phenomenon is associated with a significant increase in malonyldialdehyde (MDA) and conjugated diene generation, suggesting a relationship between histamine release and membrane lipid peroxidation. The secretion of histamine was inhibited by anti-free radical interventions such as D-mannitol, reduced glutathione and alpha-tocopherol. Some cyclooxygenase and lipoxygenase inhibitors, cimetidine and carnitine derivatives, are differentially active in the inhibition of mast cell histamine release by activated arachidonic acid. These results suggest that free radical derivatives of PUFA, generated by metabolic activation, trigger mast cell histamine release.

Pregnancy Outcomes Following Use of Escitalopram: A Prospective Comparative Cohort Study

Escitalopram is a serotonin reuptake inhibitor prescribed for depression and anxiety. There is a paucity of information regarding safety in pregnancy. The objective of this study was to determine whether escitalopram is associated with an increased risk for major malformations or other adverse outcomes following use in pregnancy. The authors analyzed pregnancy outcomes in women exposed to escitalopram (n = 212) versus other antidepressants (n = 212) versus nonteratogenic exposures (n = 212) and compared the outcomes. Among the escitalopram exposures were 172 (81%) live births, 32 (15%) spontaneous abortions, 6 (2.8%) therapeutic abortions, 3 stillbirths (1.7%), and 3 major malformations (1.7%). The only significant differences among groups was the rate of low birth weight (<2500 g) and overall mean birth weight (P = .225). However, spontaneous abortion rates were higher in both antidepressant groups (15% and 16%) compared with controls (8.5%; P = .066). There were lower rates of live births (P = .006), lower overall birth weight (P <.001), and increased rates of low birth weight (<2500 g; P = .009) with escitalopram. Spontaneous abortion rates were nearly double in both antidepressant groups (15% and 16%) compared with controls (8.5%) but not significant (P = .066). Escitalopram does not appear to be associated with an increased risk for major malformations but appears to increase the risk for low birth weight, which was correlated with the increase in infants weighing <2500 g. In addition, the higher rates of spontaneous abortions in both antidepressant groups confirmed previous findings.

Ischemia reperfusion injury and histamine release in isolated and perfused guinea-pig heart: Pharmacological interventions

Experiments were carried out to provide further information on the biochemical and morphological changes occurring in the guinea-pig heart after multiple ligature and reopening of the left anterior descending (LAD) coronary artery. In isolated perfused guinea-pig heart the reopening of LAD coronary artery leads to a release of histamine related to a loss of metachromasia by cardiac mast cells. The process is associated with malonyldialdehyde (MDA) production, cellular overload of calcium and ventricular arrhythmias which can be modulated by pharmacological interventions.

Impairment of the L-arginine-nitric oxide pathway in mast cells from spontaneously hypertensive rats

Serosal mast cells (MC) from 6 month old spontaneously hypertensive rats (SHR) were compared to MC from 6 month old Wistar Kyoto rats (WKYR) for their ability to release nitric oxide (NO). The relationship between histamine release and NO-like activity from these cells was also investigated. MC from SHR released less NO-like factor than MC from WKYR as assessed by the use of platelet aggregation and soluble guanylate cyclase activation as bioassays for NO. Sodium nitroprusside elevated the concentrations of cGMP to a similar extent in MC from SHR or WKYR. No changes in the levels of cAMP were observed. The release of histamine from MC induced by compound 48/80 or the calcium ionophore A23187 was greater in MC from SHR than in MC from WKYR. Thus, MC from SHR show a decreased production of NO-like activity which is reflected by a decreased ability to inhibit platelet aggregation. The decreased production of cGMP in the MC leads to an increased stimulated release of histamine.

Ischemia-reperfusion injury and histamine release in isolated guinea-pig heart: the role of free radicals.

Free radicals produced by the occlusion and opening of the left anterior descending coronary artery and/or by perfusion of isolated guinea-pig heart with FeCl3/ADP (10 μM/100 μM) induce a differential release of histamine and lactate dehydrogenase (LDH) in the perfusates with a preferential liberation of histamine in the reperfusion phase, associated with an increase of ventricular arrhythmias. The release of histamine has been correlated with malonyldialdehyde (MDA) production and tissue calcium content in left ventricular tissue. MDA increased during ischemia, while the calcium content increased when the tissue was reperfused. Under these conditions, N-t-butyl-α-phenylnitrone (BPN), a molecule capable of forming spin adducts with free radicals, andd-mannitol are active in preventing reperfusion-induced arrhythmias.