Novel Hemodynamic, Vascular Lesion, and Cytokine/Chemokine Differences Regarding Sex in a Pulmonary Arterial Hypertension Model.

Sex differences are recognized in pulmonary hypertension. However, the progression of disease with regard to vascular lesion formation and circulating cytokines/chemokines is unknown. To determine whether vascular lesion formation, changes in hemodynamics, and alterations in circulating chemokines/cytokines differ between males and females, we used a progressive model of pulmonary arterial hypertension (PAH), Sugen/hypoxia, and analyzed cohorts of male and female rats at time points suggested to indicate worsening disease. Our analysis included echocardiography for hemodynamics, morphometry, immunofluoresecence, and chemokine/cytokine analysis of plasma at each time point in both sexes. We found that male rats had significantly increased Fulton index, compared with those for females at each time point, as well as increased medial artery thickening at 8 weeks of PAH. Furthermore, females exhibited fewer obliterative vascular lesions than males at our latest time point. Our data also show increased IL-4, granulocyte-macrophage colony-stimulating factor, IL-10, and macrophage interacting protein-1α that were not observed in females, whereas females were observed to have increased RANTES (whose name derives from Regulated upon Activation, Normal T Cell Expressed and Presumably Secreted) and CXCL-10 that were not found in males. Males also have increased infiltrating macrophages in vascular lesions, compared with females. We found that development of progressive PAH in hemodynamics, morphology, and chemokine/cytokine circulation differs significantly between males and females. These data suggest a macrophage-driven pathology in males, whereas there may be T cell protection from vascular damage in females with PAH.

Differences in the expression of DNA methyltransferases and demethylases in leukocytes and the severity of pulmonary arterial hypertension between ethnic groups.

The loss of ten-eleven translocation (TET2) methylcytosine dioxygenase expression contributes to the pathobiology of pulmonary arterial hypertension (PAH). However, whether the expression and activity of other TETs and DNA methyltransferases (DNMTs) are altered in PAH remains enigmatic. Therefore, our objective was to determine the expression of DNMT (1, 3a, and 3b) and TET (1, 2, and 3) and their total activity. We assessed the expression of DNMT and TET enzymes in the leukocytes and their activity in extracellular vesicles (EVs). Expression of DNMT (1, 3a, and 3b), TET (2 and 3) in leukocytes, and total activity in EVs, from PAH patients was higher than in healthy controls. Additionally, we noticed there were difference in expression of these epigenetic enzyme based on ethnicity and found higher DNMT1 and lower TET2/TET3 expression in Caucasian than Hispanic/African American (combine) patients. Since loss-of-function mutation(s) and down-regulation of TET enzymes are associated with hematological malignancies and cytokine production, we determined the expression of genes that encode cytokines in samples of Caucasian and Hispanic/African American patients. Expression of IL6, CSF2, and CCL5 genes were higher in the leukocytes of Caucasian than Hispanic/African American patients, and CSF2 and CCL5 negatively correlated with the decreased expression of TET3. Interestingly, the expression of gene encoding CD34, a marker of myeloid and lymphoid precursor cells, and CD163, a monocyte/macrophage protein, was higher in the leukocytes of Caucasian than Hispanic/African American patients. Furthermore, Hispanic/African American patients having higher TET2/TET3 expression had higher pulmonary capillary wedge pressure. In conclusion, our results revealed higher DNMT1 and lower TET2/TET3 in Caucasian than Hispanic/African American patients together potentially augmented genes encoding inflammation causing cytokines, and CD34+ -derived immunogenic cells, and the severity of PAH.

Extracellular vesicle-induced cyclic AMP signaling.

Second messenger signaling is required for cellular processes. We previously reported that extracellular vesicles (EVs) from stimulated cultured endothelial cells contain the biochemical second messenger, cAMP. In the current study, we sought to determine whether cAMP-enriched EVs induce second messenger signaling pathways in naïve recipient cells. Our results indicate that cAMP-enriched EVs increase cAMP content sufficient to stimulate PKA activity. The implications of our work are that EVs represent a novel intercellular mechanism for second messenger, specifically cAMP, signaling.

Extracellular cAMP: The Past and Visiting the Future in cAMP-Enriched Extracellular Vesicles.

It is recently discovered that the cyclic nucleotide, cyclic adenosine monophosphate (cAMP) can be enriched in the extracellular vesicles (EVs) isolated from endothelial cells. In the current perspective a historical context for the discovery of the extracellular cAMP is provided. The story of extracellular cAMP through investigations addressing the molecule's role in the adenosine pathway is followed, which is widespread in mammalian physiology. The adenosine pathway mediates normal physiological conditions such as renin release, phosphate transport, etc., and participates in pathological conditions such as bronchoconstriction of the airways. Furthermore, adenosine mediated biological pathways are regulated via the receptor mediated intracellular cAMP pathway in mammalian cells. It then speculates on the question of whether cAMP enriched EVs could bypass typical receptor mediated cell signaling and directly activate cAMP signaling cascade in target cells. Preliminary studies to suggest cAMP enriched EVs are provided, added to naïve endothelial cells, results in an increase in intracellular cAMP. An alternate mechanism is proposed, apart from the traditional adenosine pathway, that extracellular cAMP may exert its effects and put into perspective how it might consider circulating cAMP moving forward.