Identification of plasma protein biomarkers associated with idiopathic pulmonary arterial hypertension.

We have employed SELDI-TOF MS to screen for differentially expressed proteins in plasma samples from 27 patients with idiopathic pulmonary arterial hypertension (IPAH) and 26 healthy controls. One ion (m/z approximately 8600) that was found to be elevated in IPAH was validated by SELDI-TOF MS analysis of a second and separate set of plasma samples comprising 30 IPAH patients and 19 controls. The m/z 8600 was purified from plasma by sequential ion exchange and reverse-phase chromatographies and SDS-PAGE. It was identified, following trypsin digestion, by MS peptide analysis as the complement component, complement 4a (C4a) des Arg. Plasma levels of C4a des Arg measured by ELISA confirmed that the levels were significantly higher (p < 0.0001) in IPAH patients (2.12 +/- 0.27 microg/mL) compared with normal controls (0.53 +/- 0.05 microg/mL). A cut-off level of 0.6 microg/mL correctly classified 92% of IPAH patients and 80% of controls. Further studies will be needed to determine its performance as a diagnostic biomarker, whether used alone or in combination with other biomarkers. Nevertheless, this study demonstrates that putative biomarkers characteristic of IPAH can be identified using a conjoint SELDI-TOF MS - proteomics approach.

Genetic association of the serotonin transporter in pulmonary arterial hypertension.

RATIONALE: The bone morphogenetic receptor type II gene is the major genetic determinant for the inherited form of pulmonary arterial hypertension. However, deleterious mutations of this gene are not observed in the majority of subjects who develop the condition spontaneously and familial disease displays age- and sex-dependent penetrance, indicating the requirement for additional environmental and/or genetic modifiers for disease development. METHODS: We investigated polymorphic variation of the serotonin transporter gene, a biological candidate for predisposition to this vascular disorder. RESULTS: No significant evidence of association between alleles of the serotonin transporter gene and pulmonary hypertension was detected, nor did we observe a relationship with age of onset in familial and idiopathic disease. CONCLUSIONS: Variation of the serotonin transporter gene appears unlikely to confer significant susceptibility to pulmonary arterial hypertension. This study emphasizes the need for adequately powered cohorts for association analyses to identify not only genetic determinants of disease susceptibility but also inherited modifiers for disease development.