Sylvain Chemtob

Localization of Functional Prostaglandin E2 Receptors EP3 and EP4 in the Nuclear Envelope

The effects of prostaglandin E2are thought to be mediated via G protein-coupled plasma membrane receptors, termed EP. However recent data implied that prostanoids may also act intracellularly. We investigated if the ubiquitous EP3 and the EP4 receptors are localized in nuclear membranes. Radioligand binding studies on isolated nuclear membrane fractions of neonatal porcine brain and adult rat liver revealed the presence of EP3 and EP4. A perinuclear localization of EP3α and EP4receptors was visualized by indirect immunocytofluorescence and confocal microscopy in porcine cerebral microvascular endothelial cells and in transfected HEK 293 cells that stably overexpress these receptors. Immunoelectron microscopy clearly revealed EP3α and EP4 receptors localization in the nuclear envelope of endothelial cells; this is the first demonstration of the nuclear localization of these receptors. Data also reveal that nuclear EP receptors are functional as they affect transcription of genes such as inducible nitric-oxide synthase and intranuclear calcium transients; this appears to involve pertussis toxin-sensitive G proteins. These results define a possible molecular mechanism of action of nuclear EP3 receptors.

Expression of cyclooxygenases in ductus arteriosus of fetal and newborn pigs

OBJECTIVEnWe studied the ontogeny of the expression of cyclooxygenase-1 and cyclooxygenase-2 in the ductus arteriosus and evaluated their functional significance.nnnSTUDY DESIGNnThe expression of cyclooxygenase-1 and cyclooxygenase-2 was studied in ductus arteriosus of fetal (at approximately 75% gestation) and term newborn pig. Effects of selective inhibitors of cyclooxygenase-1 and cyclooxygenase-2 on ductal patency were evaluated by Doppler ultrasonography.nnnRESULTSnDuctus arteriosus of the fetus expressed virtually only cyclooxygenase-1 immunoreactive protein and activity. In contrast, the ductus of the term newborn pig (<45 minutes old) contained proteins of both cyclooxygenase-1 and cyclooxygenase-2, but the latter contributed to >90% of prostaglandin E2 formation. The selective cyclooxygenase-2 inhibitor DuP697 reduced prostaglandin E2 levels in the ductus arteriosus, albeit not in plasma, but did not affect ductal patency in the newborn pig (<1(1/2) hours old); in contrast, the cyclooxygenase-1 inhibitor valeryl salicylate, like indomethacin, markedly reduced levels of prostaglandin E2 in the plasma and ductus arteriosus and caused significant constriction of the ductus arteriosus.nnnCONCLUSIONnThe ductus arteriosus of the term newborn pig, in contrast to that of the fetus, expresses cyclooxygenase-2, but circulating prostaglandins, arising mostly from cyclooxygenase-1, seem to exert the major control on ductal patency in vivo. Our data suggest that cyclooxygenase-2 inhibitors might be better alternatives for the fetus than nonselective cyclooxygenase blockers if indicated for maternal conditions such as inflammation or for tocolysis.

Carbon Monoxide: From Public Health Risk to Painless Killer

The omnipresent colorless and odorless carbon monoxide (CO), generated by combustion, is the leading cause of unintentional death worldwide. CO binds to hemoglobin with affinity more than 200-times greater than oxygen and forms carboxyhemoglobin (COHb). The source of the endogenous CO is the breakdown of heme by heme oxygenase (HO), yielding CO, biliverdin, and iron; endogenous CO is similar to another endogenous gas, nitric oxide (NO), and both activate guanylyl cyclase and increase cGMP, which mediates many of their physiological effects. The toxicity of CO is primarily attributable to formation of COHb and resultant hypoxia, which in turn leads to rebound hyperperfusion and generation of oxidant radicals; these oxidants can produce their own toxicity and add to that of CO. The toxicity of CO ranges from mild headache at COHb less than 10% to death at COHb more than 70%. CO is more toxic in subjects with cardiovascular diseases than in healthy individuals, and it increases maternal and fetal morbidity and mortality. Nonfatal exposure to CO can result in delayed neurological, myocardial, and other toxicities. At the same time, there is some adaptation to effects of CO on low level chronic exposure. Hyperbaric oxygen is the main therapy against CO poisoning. Determined public health measures are needed to decrease atmospheric CO, which is already quite high in places such as Mexico City and Los Angeles.

Chapter 21 – Carbon Monoxide: From Public Health Risk to Painless Killer

The omnipresent colorless and odorless carbon monoxide (CO), generated by combustion, is the leading cause of unintentional death worldwide. CO binds to hemoglobin with affinity more than 200-times greater than oxygen and forms carboxyhemoglobin (COHb). The source of the endogenous CO is the breakdown of heme by heme oxygenase (HO), yielding CO, biliverdin, and iron; endogenous CO is similar to another endogenous gas, nitric oxide (NO), and both activate guanylyl cyclase and increase cGMP, which mediates many of their physiological effects. The toxicity of CO is primarily attributable to formation of COHb and resultant hypoxia, which in turn leads to rebound hyperperfusion and generation of oxidant radicals; these oxidants can produce their own toxicity and add to that of CO. The toxicity of CO ranges from mild headache at COHb less than 10% to death at COHb more than 70%. CO is more toxic in subjects with cardiovascular diseases than in healthy individuals, and it increases maternal and fetal morbidity and mortality. Nonfatal exposure to CO can result in delayed neurological, myocardial, and other toxicities. At the same time, there is some adaptation to effects of CO on low level chronic exposure. Hyperbaric oxygen is the main therapy against CO poisoning. Determined public health measures are needed to decrease atmospheric CO, which is already quite high in places such as Mexico City and Los Angeles.

Synthesis and Evaluation of Azapeptide Prostaglandin F2α Receptor Modulators in Pursuit of Inhibitors of Preterm Labor

The incidence of preterm birth has been steadily increasing over the past thirty years, and presently, preterm delivery accounts for >75% of all neonatal deaths [1]. The prostaglandin F2α receptor (FP) is responsible for initiating labor and preterm labor [2]. In pursuit of drugs to delay uterine contractions and prolong pregnancy, FP has been targeted based on peptide leads using a peptidomimetic approach. For example, the indolizidin-2-one amino acid analogue PDC113.824 (1) [3] and aza-phenylalanine analogue 2 (Figure 1) [4], both reduced prostaglandin-F2α-induced myometrial contractions by modulating G protein signaling pathways. Studies of structure-activity relationships of aza-amino acyl proline modulators such as 2 have shown that biological activity was contingent on the aza-amino acyl residue side chain [4]. Considering that structural modification of the aza-residue may have consequences on function, we are exploring diversity-oriented synthesis featuring alkylation of the aza-glycinyl-proline residue to introduce different side chains onto the aza-peptide modulators. In this report, we describe the synthesis of aza-p-methylphenylalanine analogue 3.