Pulmonary artery smooth muscle cell HIF-1α regulates endothelin expression via microRNA-543.

Pulmonary artery smooth muscle cells (PASMCs) express endothelin (ET-1), which modulates the pulmonary vascular response to hypoxia. Although cross-talk between hypoxia-inducible factor-1α (HIF-1α), an O2-sensitive transcription factor, and ET-1 is established, the cell-specific relationship between HIF-1α and ET-1 expression remains incompletely understood. We tested the hypotheses that in PASMCs 1) HIF-1α expression constrains ET-1 expression, and 2) a specific microRNA (miRNA) links HIF-1α and ET-1 expression. In human (h)PASMCs, depletion of HIF-1α with siRNA increased ET-1 expression at both the mRNA and protein levels ( P < 0.01). In HIF-1α-/- murine PASMCs, ET-1 gene and protein expression was increased ( P < 0.0001) compared with HIF-1α+/+ cells. miRNA profiles were screened in hPASMCs transfected with siRNA-HIF-1α, and RNA hybridization was performed on the Agilent (Santa Clara, CA) human miRNA microarray. With HIF-1α depletion, miRNA-543 increased 2.4-fold ( P < 0.01). In hPASMCs, miRNA-543 overexpression increased ET-1 gene ( P < 0.01) and protein ( P < 0.01) expression, decreased TWIST gene expression ( P < 0.05), and increased ET-1 gene and protein expression, compared with nontargeting controls ( P < 0.01). Moreover, we evaluated low passage hPASMCs from control and patients with idiopathic pulmonary arterial hypertension (IPAH). Compared with controls, protein expression of HIF-1α and Twist-related protein-1 (TWIST1) was decreased ( P < 0.05), and miRNA-543 and ET-1 expression increased ( P < 0.001) in hPASMCs from patients with IPAH. Thus, in PASMCs, loss of HIF-1α increases miRNA-543, which decreases Twist expression, leading to an increase in PASMC ET-1 expression. This previously undescribed link between HIF-1α and ET-1 via miRNA-543 mediated Twist suppression represents another layer of molecular regulation that might determine pulmonary vascular tone.

Cell lineage responses to photobiomodulation therapy.

Photobiomodulation (PBM) therapy has been noted to promote cell proliferation and growth in many different cell types shown both in vitro and in vivo. Currently, treatment regimens are used in the clinic for a variety of ailments, including wound healing. However, most protocols treat an anatomical site without considering individual cell types constituting the target tissues. This study investigates the maximal dose threshold for oral keratinocyte and fibroblast cell types treated with near-infrared laser therapy. We observed keratinocytes have increased sensitivity to laser irradiances (>0.047 W/cm2 , 300 sec, 14.2 J/cm2 ) compared to the fibroblast cells (>0.057 W/cm2 , 300 sec, 15.1 J/cm2 ) (p < 0.0001). Laser treatments were noted to generate increased reactive oxygen species (ROS) levels in keratinocytes compared to fibroblasts that appeared to inversely correlate with higher basal catalase expression. To validate these observations, melatonin was used to treat keratinocytes to induce catalase activity (p < 0.0001). Increased melatonin-induced catalase levels were noted to significantly improve keratinocyte survival to phototoxic laser doses. These observations suggest that clinical laser dosing should account for differential effects of lasers on individual cell types to improve safety and clinical efficacy of PBM therapy.