Primary pulmonary hypertension in a patient with a familial platelet storage pool disease: role of serotonin

Pulmonary vasculitis with hypereosinophilia and episodic pulmonary hypertension: report of three siblings

Three siblings with eosinophilia who developed pulmonary hypertension are reported. They consisted of a 3 year old boy (case 1), a 9 year old boy (case 2) and a 13 year old girl (case 3), all of whom died within an 18 month period of severe episodic attacks of pulmonary hypertension and the resultant low cardiac output. Marked peripheral eosinophilia was found in cases 1 and 2, and mild eosinophilia in case 3. Open lung biopsy of case 1 revealed pulmonary arteritis with massive eosinophilic infiltration and intimal thickening of muscular arteries of 300-1500 microns in diameter. At autopsy, cases 2 and 3 showed almost similar findings, comprising widespread obliteration of the pulmonary arteries by concentric intimal thickening, medial hypertrophy and recanalized thrombi of arterioles. Rarely, there were foci of granulomas in the thickened intima surrounding birefringent foreign bodies. There were small areas of infarction in the lungs and heart due to arterial thrombi. Vascular lesions other than those in the lungs were mild and almost limited to the branches of the coronary arteries. Therefore, the present cases appear to be a single disease of pulmonary hypertension secondary to endothelial injury and the resultant intimal fibrosis probably evoked by toxic substances, although such agents were not confirmed.

Pathology of pulmonary hypertension: a human and experimental study

To clarify the histopathological characteristics of pulmonary hypertension (PH) in Japan, and to clarify the role of serotonin and endothelin in monocrotaline induced PH, human histopathological studies and experimental studies were carried out. An epidemiological study based on the Annual of the Pathological Autopsy Cases in Japan, and a morphological study on autopsy cases of congenital heart disease and idiopathic PH were performed. Plasma levels of serotonin and endothelin, vascular responsiveness to serotonin, and the effects of a selective serotonin antagonist, DV-7028, were investigated after monocrotaline injection. Plexogenic pulmonary arteriopathy was prevalent, and recurrent pulmonary thromboembolism and pulmonary veno-occlusive disease extremely rare among primary pulmonary hypertension in Japan. In secondary PH, systemic lupus erythematosus and mixed connective tissue disease were frequent and showed particularly severe intimal and medial thickening. After an injection of monocrotaline, plasma serotonin and endothelin levels were raised, and pulmonary arteries showed hyperreactivity to serotonin. DV-7028 (5-HT2 receptor antagonist) attenuated the rise in pulmonary artery pressure and the various effects of monocrotaline. There may be some genetic difference between PH in Japan and other countries. Roles for serotonin and endothelin in the initiation and progression of monocrotaline induced PH are suggested.

An imbalance between the excretion of thromboxane and prostacyclin metabolites in pulmonary hypertension

BACKGROUND

Constriction of small pulmonary arteries and arterioles and focal vascular injury are features of pulmonary hypertension. Because thromboxane A2 is both a vasoconstrictor and a potent stimulus for platelet aggregation, it may be an important mediator of pulmonary hypertension. Its effects are antagonized by prostacyclin, which is released by vascular endothelial cells. We tested the hypothesis that there may be an imbalance between the release of thromboxane A2 and prostacyclin in pulmonary hypertension, reflecting platelet activation and an abnormal response of the pulmonary vascular endothelium.

METHODS

We used radioimmunoassays to measure the 24-hour urinary excretion of two stable metabolites of thromboxane A2 and a metabolite of prostacyclin in 20 patients with primary pulmonary hypertension, 14 with secondary pulmonary hypertension, 9 with severe chronic obstructive pulmonary disease (COPD) but no clinical evidence of pulmonary hypertension, and 23 normal controls.

RESULTS

The 24-hour excretion of 11-dehydro-thromboxane B2 (a stable metabolite of thromboxane A2) was increased in patients with primary pulmonary hypertension and patients with secondary pulmonary hypertension, as compared with normal controls (3224 +/- 482, 5392 +/- 1640, and 1145 +/- 221 pg per milligram of creatinine, respectively; P less than 0.05), whereas the 24-hour excretion of 2,3-dinor-6-keto-prostaglandin F1 alpha (a stable metabolite of prostacyclin) was decreased (369 +/- 106, 304 +/- 76, and 644 +/- 124 pg per milligram of creatinine, respectively; P less than 0.05). The rate of excretion of all metabolites in the patients with COPD but no clinical evidence of pulmonary hypertension was similar to that in the normal controls.

CONCLUSIONS

An increase in the release of the vasoconstrictor thromboxane A2, suggesting the activation of platelets, occurs in both the primary and secondary forms of pulmonary hypertension. By contrast, the release of prostacyclin is depressed in these patients. Whether the imbalance in the release of these mediators is a cause or a result of pulmonary hypertension is unknown, but it may play a part in the development and maintenance of both forms of the disorder.