Pulmonary hypertension (PHT) occurs in ~30% of patients with sickle cell anemia (SCA) and results in ~50% mortality within 2 years of diagnosis. The pathogenesis of this vasculopathy is likely multi-factorial, potentiated by hemolysis-induced impaired nitric oxide bioavailability, chronic thrombo-embolism from a procoagulant state, and increased endothelin-1 (ET-1). Our studies have shown that placenta growth factor (PlGF), an angiogenic growth factor produced in high amounts by sickle erythroid cells, induces expression of the potent pulmonary vasoconstrictor ET-1, and a procoagulant, plasminogen activator inhibitor-1 (PAI-1), from human pulmonary microvascular endothelial cells (HPMVEC). PlGF increases ET-1 and PAI-1 expression via induction of hypoxia-inducible factor-1? (HIF-1?). PHT can be induced experimentally by ectopic PlGF expression in normal mice characterized by increased ET-1, as is observed in transgenic sickle mice and in SCA patients. We recently observed that PlGF-mediated induction of HIF-1? and PAI-1 in HPMVEC is post- transcriptionally regulated by three specific microRNAs (miRs). Relatively little is known of the post- transcriptional, miR-mediated, regulated expression of HIF-1a, ET-1 and PAI-1, or of the RNA-binding proteins that stabilize the mRNAs of these genes that promote PHT. Thus our overall hypothesis is that cytoplasmic RNA-binding proteins and miRNAs alter the stability of HIF-1?, ET-1, and PAI-1 mRNAs, and are directly involved in the development of PHT. To address this hypothesis, in Aim 1, we will determine the post- transcriptional mechanisms which regulate PlGF-mediated expression of HIF-1a, ET-1 and PAI-1 and identify RNA binding proteins and the specific miRs involved in binding to mRNA 3'UTRs thus regulating translation of HIF-1a, ET-1, and PAI-1 mRNAs.
In Aim 2, we will determine whether the genes for miRs that regulate PAI-1 expression, and are located within introns of NFYC and SKA2 genes are co-synthesized from the NFYC and SKA2 primary transcripts, or are independently transcribed from a smaller, pre-miRNA transcription unit.
In Aim 3, we will demonstrate the requirement of these miRs in the regulation of HIF-1?, ET-1 and PAI-1 in genetic mouse models that over-express PlGF and develop PHT. Finally, we will determine the association of plasma levels of these miRNAs to plasma PlGF, ET-1 and PAI-1 in SCA patients with and without PHT symptoms. These studies will advance our knowledge as to how RNA binding proteins and miRs regulate some of the key genes involved in sickle PHT, and how expression of these miRNAs is itself regulated. These studies will likely provide new diagnostic bio-markers for assessment of PHT, and novel therapeutic targets for a disease that currently has few or no therapeutic options.
Pulmonary hypertension (PHT) is associated with high death rate among sickle cell anemia patients. We have found that genes (e.g. endothelin-1) associated with PHT are increased in these patients, and we propose to study specific microRNAs involved in their regulation.
|Kalra, Vijay K; Zhang, Shuxiao; Malik, Punam et al. (2018) Placenta growth factor mediated gene regulation in sickle cell disease. Blood Rev 32:61-70|
|Eiymo Mwa Mpollo, Marthe-Sandrine; Brandt, Eric B; Shanmukhappa, Shiva Kumar et al. (2016) Placenta growth factor augments airway hyperresponsiveness via leukotrienes and IL-13. J Clin Invest 126:571-84|
|Li, Chen; Zhou, Yu; Loberg, Anastacia et al. (2016) Activated Transcription Factor 3 in Association with Histone Deacetylase 6 Negatively Regulates MicroRNA 199a2 Transcription by Chromatin Remodeling and Reduces Endothelin-1 Expression. Mol Cell Biol 36:2838-2854|
|Gonsalves, Caryn S; Li, Chen; Mpollo, Marthe-Sandrine Eiymo Mwa et al. (2015) Erythropoietin-mediated expression of placenta growth factor is regulated via activation of hypoxia-inducible factor-1? and post-transcriptionally by miR-214 in sickle cell disease. Biochem J 468:409-23|
|Li, Chen; Gonsalves, Caryn S; Eiymo Mwa Mpollo, Marthe-Sandrine et al. (2015) MicroRNA 648 Targets ET-1 mRNA and is cotranscriptionally regulated with MICAL3 by PAX5. Mol Cell Biol 35:514-28|
|Gonsalves, Caryn S; Li, Chen; Malik, Punam et al. (2015) Peroxisome proliferator-activated receptor-?-mediated transcription of miR-301a and miR-454 and their host gene SKA2 regulates endothelin-1 and PAI-1 expression in sickle cell disease. Biosci Rep 35:|
|Li, Chen; Mpollo, Marthe-Sandrine Eiymo Mwa; Gonsalves, Caryn S et al. (2014) Peroxisome proliferator-activated receptor-?-mediated transcription of miR-199a2 attenuates endothelin-1 expression via hypoxia-inducible factor-1?. J Biol Chem 289:36031-47|
|Ferreira, Raquel; Santos, Tiago; Amar, Arun et al. (2014) Argonaute-2 promotes miR-18a entry in human brain endothelial cells. J Am Heart Assoc 3:e000968|