Dioxotriazine derivatives as a new class of P2X3 receptor antagonists: Identification of a lead and initial SAR studies.

P2X3 receptor is an ATP-gated ion channel, mainly localized on peripheral sensory neurons. Currently, several clinical trials are being conducted with P2X3 receptor antagonists for the treatment of chronic pain or cough. To identify a P2X3 lead compound, we reexamined the HTS evaluation compounds and selected dioxotriazine derivatives from which we identified a hit compound. As a result of the hit-to-lead SAR, we obtained lead compound 1 which had a moderate inhibitory effect on P2X3 receptors (IC50, 128 nM). Further improvement of the potency and PK profiles of this lead compound finally led to the selected compound 74 (P2X3 IC50, 16.1 nM; P2X2/3 IC50, 2931 nM), which demonstrated a strong analgesic effect against allodynia on oral administration in the rat partial sciatic nerve ligation model of neuropathic pain (ED50, 3.1 mg/kg).

Pyrrolinone derivatives as a new class of P2X3 receptor antagonists. Part 3: Structure-activity relationships of pyrropyrazolone derivatives.

The P2X3 receptor is an attractive target for the treatment of pain and chronic coughing, and thus P2X3 antagonists have been developed as new therapeutic drugs. We previously reported selective P2X3 receptor antagonists by derivatization of hit compound 1. As a result, we identified hit compound 3, the structure of which was similar to hit compound 1. On the basis of SAR studies of hit compound 1, we modified hit compound 3 and compound 42 was identified as having analgesic efficacy by oral administration.

Pyrrolinone derivatives as a new class of P2X3 receptor antagonists Part 2: Discovery of orally bioavailable compounds.

Some P2X3 receptor antagonists have been developed as new therapeutic drugs for pain. We discovered a novel chemotype of P2X3 receptor antagonists with a pyrrolinone skeleton. Because of SAR studies to improve bioavailability of lead compound 2, compound (R)-24 was identified, which showed an analgesic effect against neuropathic pain by oral administration. We constructed a human P2X3 homology model as a template for the zebrafish P2X4 receptor, which agreed with SAR studies of pyrrolinone derivatives.

Pyrrolinone derivatives as a new class of P2X3 receptor antagonists. Part 1: Initial structure-activity relationship studies of a hit from a high throughput screening.

The P2X3 receptor is primarily expressed in the peripheral sensory nerves, and therefore, antagonists of this receptor may be useful for the treatment of chronic pain. Pyrrolinone derivatives have been identified as a novel class of P2X3 receptor antagonists. A lead structure with moderate activity was discovered through a high-throughput screening assay. A structure-activity study led to the discovery of several P2X3 receptor antagonists. Compound 34 showed potent and specific antagonistic activity and analgesic efficacy.

Maintenance of pulmonary vasculature tone by blood derived from the inferior vena cava in a rabbit model of cavopulmonary shunt.

INTRODUCTION: After cavopulmonary shunt in which the superior vena cava is anastomosed to the right pulmonary artery, the right lung is in a unique condition without flow pulsatility and hepatic venous effluent. In a previous study, we reported that hypoxic pulmonary vasoconstriction disappeared in the pulmonary circulation after cavopulmonary shunt. In this study, however, to investigate the influence of pulsatility and hepatic venous effluent on hypoxic pulmonary vasoconstriction in the pulmonary circulation, we developed an alternative cavopulmonary shunt rabbit model that included hepatic venous effluent in the pulmonary circulation and reduced the pulsatility of the pulmonary arterial blood flow. We then observed the physiologic characteristics of the peripheral pulmonary artery after cavopulmonary shunt, specifically the disappearance of hypoxic pulmonary vasoconstriction. METHODS: Sixteen Japanese white rabbits (12-16 weeks old) were used in this study. With general anesthesia, a cavopulmonary shunt was established by anastomosing the right superior vena cava to the right pulmonary artery in an end-to-side fashion. Of the 16 rabbits for the study, the proximal right pulmonary artery was completely ligated in 5 (atresia group) and partially ligated in 6 (stenosis group). Sham operation was performed in the remaining 5 rabbits. Two weeks later, we analyzed the response of the pulmonary artery (which was divided into three categories: segmental, lobular, and acinar level artery) to hypoxia (8% oxygen inhalation) with a specially designed video radiographic system. Morphometric analysis of the resistance pulmonary artery was done in each group after angiography. RESULTS: Mean pressure and pulse pressure in the right pulmonary artery were not significantly different between the atresia and stenosis groups. The mean pulmonary artery pressures in the atresia and stenosis groups were 8 and 11 mm Hg, respectively. However, the pulse pressure was less than 2 mm Hg in both groups. The baseline internal diameter of the resistance pulmonary artery of the atresia group was significantly different from those of the stenosis and sham groups. In the atresia group, the resistance pulmonary arteries did not respond to hypoxia. In contrast, significant constriction (as assessed by percentage change of internal diameter of the resistance pulmonary arteries in the acinar and lobular level arteries) was observed in the pulmonary arteries of the sham and stenosis groups (atresia vs stenosis vs sham 0.4% vs - 19.0% vs - 18.8%, P = .01). In our morphometric study, we observed vasodilation of the resistance pulmonary artery with a thinner medial layer in the atresia group, consistent with the result of microangiography. CONCLUSION: We developed a cavopulmonary shunt rabbit model in which the inferior vena caval blood was derived from the right ventricle. Hypoxic pulmonary vasoconstriction was maintained in the model with the blood flow from the right ventricle. When the blood flow was not maintained, however, hypoxic pulmonary vasoconstriction disappeared. This phenomenon strongly suggests that a substance in hepatic venous effluent partially regulates the physiological pulmonary vascular function in the rabbit lung.

Infective endocarditis developing as uremia.

A 49-year-old man presented with fever and uremic symptoms such as general malaise, leg edema and decreased urine output. He was diagnosed as having infective endocarditis (IE) accompanied by renal failure. Although he had been receiving hemodialysis for a long time, renal function dramatically improved after heart valve replacement. This case suggests that uremia can develop as an initial manifestation of IE and removal of an infected heart valve can improve renal function despite persistent renal failure. From the perspective of recovery of renal function, early surgery should be considered in patients with renal failure following IE.

Hypoxic pulmonary vasoconstriction disappears in a rabbit model of cavopulmonary shunt.

BACKGROUND: Cavopulmonary shunt is widely known as an interim staging procedure in patients with single-ventricle physiology. However, the physiologic characteristics of the pulmonary arterial system after cavopulmonary shunt are not clearly understood. In this article, we developed a rabbit cavopulmonary shunt model and studied the morphologic changes and physiologic characteristics (namely, hypoxic pulmonary vasoconstriction) of pulmonary arteries after cavopulmonary shunt. METHODS: Male Japanese white rabbits aged 12 to 16 weeks were used for the study. In 5 rabbits, the superior vena cava was anastomosed to the right pulmonary artery in an end-to-side fashion, followed by a proximal side ligation of the right pulmonary artery (cavopulmonary shunt group). In 4 rabbits, the superior vena cava and the right pulmonary artery were dissected and clamped for 10 minutes without making a cavopulmonary shunt (sham group). Two weeks after the operation, we then measured the internal diameter of the acinar (internal diameter, 164 +/- 7 microm), the lobular (305 +/- 13 microm), and the segmental (669 +/- 16 microm) pulmonary arteries in both controlled and hypoxic conditions by using a specially designed x-ray television system. Also, morphometric measurements were made in the pulmonary arteries around the terminal bronchioles. RESULTS: Two weeks after the operation, the arterial oxygen tension under room air conditions was significantly lower in the cavopulmonary shunt group than in the sham group (68.2 +/- 2.2 mm Hg vs 91.1 +/- 1.9 mm Hg; P =.01). The baseline internal diameters in the acinar and the lobular (resistance), but not the segmental (conduit), pulmonary arteries on the anastomosed side of the cavopulmonary shunt group were significantly larger than those of pulmonary arteries on the nonanastomosed side of the cavopulmonary shunt group and the sham group. Moreover, the pulmonary arteries on the anastomosed side of the cavopulmonary shunt group did not respond to hypoxia, whereas those on the nonanastomosed side of the cavopulmonary shunt and sham groups did have local internal diameter reductions in the acinar and lobular arteries (-1.1% +/- 1.0% in the anastomosed side vs -17.7% +/- 3.5% in the nonanastomosed side vs -20.9% +/- 6.1% in the sham group; P =.03). In the morphometric studies, the internal diameter of the pulmonary artery accompanying the terminal bronchiole in the anastomosed side of the cavopulmonary shunt group was significantly larger, and the ratio of medial thickness relative to the outer diameter was smaller compared with ratios in the nonanastomosed side of the cavopulmonary shunt group and the sham group. CONCLUSIONS: We developed a rabbit cavopulmonary shunt model. In the anastomosed side of the cavopulmonary shunt group, the peripheral pulmonary arteries, which contributed greatly in regulating the pulmonary vascular resistance, had a local reduction in the basal vascular tone and no hypoxic vasoconstriction 2 weeks after the operation.

Visualization of intramuscular left anterior descending coronary arteries during off-pump bypass surgery.

In off-pump coronary artery bypass surgery, an appropriate method for intraoperative evaluation of grafts and vessels has been awaited. We report the usefulness of a 15-MHz linear transducer for this purpose. A 15-MHz linear transducer with a SONOS 5500 (Philips Medical Systems, Best, Netherlands) was applied epicardially in off-pump coronary artery bypass surgery patients. Vascular anatomy was easily discerned when the transducer was applied in an appropriate way. In 6 patients, intramuscular coronary arteries were easily detected, and in all of these patients, anastomoses were successful. The shapes of the anastomoses were very clearly shown, and the flow and its phase in the bypass graft or coronary artery were measured with synchronization of electrocardiograms in all patients. The total left internal thoracic artery (LITA) flow (28.4 +/- 6.8 mL/s) and the pattern of the flow was dominantly diastolic in all patients. The 15-MHz linear transducer system (Philips) is very useful for detecting intramuscular left anterior descending coronary arteries and may become one of the standard tools for intraoperative evaluation in off-pump coronary artery bypass surgery.

Production and characterization of biosurfactants from Bacillus licheniformis F2.2.

A biosurfactant-producing strain, Bacillus licheniformis F2.2, was isolated from a fermented food in Thailand. The strain was capable of producing a new biosurfactant, BL1193, as well as two kinds of popular lipopeptide biosurfactants, plipastatin and surfactin. Mass spectrometry and FT-IR analysis indicated that BL1193 had a molecular mass of 1,193 Da with no peptide portion in the molecule. While plipastatin and surfactin were abundantly produced in a nutrient YPD medium, BL1193 was produced only in a synthetic DF medium containing no amino acids. According to an oil displacement activity test, the specific activity of BL1193 (6.53 kBS units/mg) is equivalent to that of surfactin (5.78-6.83 kBS units/mg).

Isolation and characterization of a halotolerant Bacillus subtilis BBK-1 which produces three kinds of lipopeptides: bacillomycin L, plipastatin, and surfactin.

Twenty-three halotolerant and biosurfactant producing strains were collected from salty conditions in central Thailand. One of the strains designated BBK-1 produced the biosurfactants with the highest activity. BBK-1 was isolated from fermented foods and was identified as B. subtilis based on its physiological characteristics and 16S rRNA gene sequence. We show that the strain grows in media containing NaCl up to 16% (w/v) and produces biosurfactants in NaCl up to 8%. We found that B. subtilis BBK-1 produces three kinds of surface-active lipopeptides simultaneously. By their respective molecular weights and amino acid compositions, it is indicated that these lipopeptides are bacillomycin L, plipastatin, and surfactin. In order to analyze the production mechanism of lipopeptides further in the strain, a generally important biosynthetic gene encoding 4'-phosphopantetheinyl transferase was cloned and sequenced. The gene existed in a single copy in the genome and the deduced amino acid sequence was almost identical to that of Lpa-14 from B. subtilis strain RB14, which co-produces iturin A and surfactin.