Pathology of pulmonary hypertension

Pyrrolizidine alkaloids in food: a spectrum of potential health consequences

Contamination of grain with 1,2-dehydropyrrolizidine ester alkaloids (dehydroPAs) and their N-oxides is responsible for large incidents of acute and subacute food poisoning, with high morbidity and mortality, in Africa and in central and south Asia. Herbal medicines and teas containing dehydroPAs have also caused fatalities in both developed and developing countries. There is now increasing recognition that some staple and widely consumed foods are sometimes contaminated by dehydroPAs and their N-oxides at levels that, while insufficient to cause acute poisoning, greatly exceed maximum tolerable daily intakes and/or maximum levels determined by a number of independent risk assessment authorities. This suggests that there may have been cases of disease in the past not recognised as resulting from dietary exposure to dehydroPAs. A review of the literature shows that there are a number of reports of liver disease where either exposure to dehydroPAs was suspected but no source was identified or a dehydroPA-aetiology was not considered but the symptoms and pathology suggests their involvement. DehydroPAs also cause progressive, chronic diseases such as cancer and pulmonary arterial hypertension but proof of their involvement in human cases of these chronic diseases, including sources of exposure to dehydroPAs, has generally been lacking. Growing recognition of hazardous levels of dehydroPAs in a range of common foods suggests that physicians and clinicians need to be alert to the possibility that these contaminants may, in some cases, be a possible cause of chronic diseases such as cirrhosis, pulmonary hypertension and cancer in humans.

The antiproliferative effect of sildenafil on pulmonary artery smooth muscle cells is mediated via upregulation of mitogen-activated protein kinase phosphatase-1 and degradation of extracellular signal-regulated kinase 1/2 phosphorylation

BACKGROUND

Pulmonary hypertension is a group of diseases comprising vascular constriction and by obstructive changes of the pulmonary vasculature. Phosphodiesterase type 5 inhibitors, e.g., sildenafil, can alleviate vascular remodeling in the monocrotaline pulmonary hypertension model in rats, and inhibit the proliferation of pulmonary vascular smooth muscle cells in vitro. We examined the ability of sildenafil to inhibit platelet-derived growth factor (PDGF)-induced proliferation of porcine pulmonary artery smooth muscle cells.

METHODS

Pulmonary artery smooth muscle cell proliferation and cell cycle analysis were assessed by MTT assay and fluorescence-activated cell sorting. Western blotting was used to examine protein expression of mitogen-activated protein kinase phosphatase-1 (MKP-1) and phosphorylation level of extracellular signal-regulated kinase (ERK1/2).

RESULTS

PDGF increased cell proliferation and the percentage of cells in S phase. These effects were inhibited by pretreatment with sildenafil in a dose-dependent manner. Sildenafil (96 microM) also caused a 67% decrease in PDGF-stimulated ERK1/2 phosphorylation. Sildenafil inhibition of ERK1/2 was accompanied by a rapid induction of MKP-1. Inhibition of the cGMP-dependent kinase I alpha (cGK I alpha) using Rp-8-BrcGMPS (25 microM) blocked sildenafil-induced MKP-1 expression. Either vanadate (12.5 microM), a phosphatase inhibitor, or Rp-8-BrcGMPS abolished the inhibitory effect of sildenafil on PDGF-stimulated phosphorylation of ERK1/2 and restored PDGF-induced cell proliferation.

CONCLUSION

This study indicates that sildenafil upregulates MKP-1 expression and promotes degradation of phosphorylation of ERK1/2, which suppresses the proliferation of pulmonary artery smooth muscle cells.

The use of nitric oxide in neonatal care

Knowledge of NO and its role in the human body currently is limited. Further scientific research involving this unique molecule will expand its clinical usefulness. It is an exciting era in research,involving numerous body processes and systems. The initial work on pulmonary vascular response in newborns who have PPHN has opened the door to seemingly endless possibilities involving many aspects of health.