Browsing by Author "Holohan, Maggie"

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    Altered Smooth Muscle Cell Histone Acetylome by the SPHK2/S1P Axis Promotes Pulmonary Hypertension
    (American Heart Association, 2023) Ranasinghe, A. Dushani C. U.; Holohan, Maggie; Borger, Kalyn M.; Donahue, Deborah L.; Kuc, Rafael D.; Gerig, Martin; Kim, Andrew; Ploplis, Victoria A.; Castellino, Francis J.; Schwarz, Margaret A.; Pediatrics, School of Medicine
    Background: Epigenetic regulation of vascular remodeling in pulmonary hypertension (PH) is poorly understood. Transcription regulating, histone acetylation code alters chromatin accessibility to promote transcriptional activation. Our goal was to identify upstream mechanisms that disrupt epigenetic equilibrium in PH. Methods: Human pulmonary artery smooth muscle cells (PASMCs), human idiopathic pulmonary arterial hypertension (iPAH):human PASMCs, iPAH lung tissue, failed donor lung tissue, human pulmonary microvascular endothelial cells, iPAH:PASMC and non-iPAH:PASMC RNA-seq databases, NanoString nCounter, and cleavage under targets and release using nuclease were utilized to investigate histone acetylation, hyperacetylation targets, protein and gene expression, sphingolipid activation, cell proliferation, and gene target identification. SPHK2 (sphingosine kinase 2) knockout was compared with control C57BL/6NJ mice after 3 weeks of hypoxia and assessed for indices of PH. Results: We identified that Human PASMCs are vulnerable to the transcription-promoting epigenetic mediator histone acetylation resulting in alterations in transcription machinery and confirmed its pathological existence in PH:PASMC cells. We report that SPHK2 is elevated as much as 20-fold in iPAH lung tissue and is elevated in iPAH:PASMC cells. During PH pathogenesis, nuclear SPHK2 activates nuclear bioactive lipid S1P (sphingosine 1-phosphate) catalyzing enzyme and mediates transcription regulating histone H3K9 acetylation (acetyl histone H3 lysine 9 [Ac-H3K9]) through EMAP (endothelial monocyte activating polypeptide) II. In iPAH lungs, we identified a 4-fold elevation of the reversible epigenetic transcription modulator Ac-H3K9:H3 ratio. Loss of SPHK2 inhibited hypoxic-induced PH and Ac-H3K9 in mice. We discovered that pulmonary vascular endothelial cells are a priming factor of the EMAP II/SPHK2/S1P axis that alters the acetylome with a specificity for PASMC, through hyperacetylation of histone H3K9. Using cleavage under targets and release using nuclease, we further show that EMAP II-mediated SPHK2 has the potential to modify the local transcription machinery of pluripotency factor KLF4 (Krüppel-like factor 4) by hyperacetylating KLF4 Cis-regulatory elements while deletion and targeted inhibition of SPHK2 rescues transcription altering Ac-H3K9. Conclusions: SPHK2 expression and its activation of the reversible histone H3K9 acetylation in human pulmonary artery smooth muscle cell represent new therapeutic targets that could mitigate PH vascular remodeling.
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    Confounding Histoplasmosis in Hodgkin’s Lymphoma
    (2022-03-24) Zhou, Shannon; Friel, Rylee; Holohan, Maggie; Geers, Erica; Alali, Muayad; Belsky, Jennifer
    Case Description: A 17-year-old, black female was diagnosed with Hodgkin’s Lymphoma (HL), confirmed with lymph node biopsy. Initial infectious workup was negative for Histoplasmosis capsulatum (H. capsulatum), and she was started on routine chemotherapy. After 2 cycles of chemotherapy, routine 18FDG/PET scan demonstrated reduction in previous mediastinal adenopathy, but new areas of adenopathy. Due to concern of disease progression in conjunction with new fevers and dyspnea, she had a biopsy which histologically confirmed H. capsulatum with positive IgG and IgM. She was started on antifungal therapy with dose reduction of chemotherapy. FDG/PET scan 5 weeks into antifungal therapy demonstrated continued FDG uptake in previous H. caspulatum concerning areas, and she was continued on both chemotherapy and antifungal therapy. Radiation to her mediastinal mass and persistent areas of FDG uptake is under discussion. Conclusion: Hodgkin lymphoma (HL) is the most common form of lymphoma and classically presents in late adolescent females as lymphadenopathy. 18FDG/PET scans are used to visualize malignant tissue and aid in staging and end of treatment assessment. We present a case of HL whose case was complicated by concurrent H. capsulatum infection, creating a clinical conundrum regarding treatment. Clinical Significance: Acute H. capsulatum infection can appear as a pulmonary consolidation and/or lymphadenopathy with FDG avidity, making it difficult to discern infection from malignancy. This often results in biopsy, chemotherapy reduction, and ambiguity regarding future radiation therapy. Future research should focus on more FDG sensitive tracers to differentiate malignant tissue from infectious or inflammatory tissue. In addition, immunosuppression in the setting of chemotherapy puts patients at risk for opportunistic infections such as H. capsulatum. Screening for opportunistic disease in endemic areas before initiating chemotherapy should be considered.