Biology subjects

Lockett, A. D.

Publications and source records attributed to Lockett, A. D..

3 recordsLinked to original sources

bioRxiv2026

Nicotinamide phosphoribosyltransferase activates the mitochondrial unfolded protein response to promote pulmonary arterial endothelial cell proliferation

Vascular remodeling leading to occlusion of the pulmonary artery and increased pulmonary vascular resistance is the central feature of Pulmonary Arterial Hypertension (PAH) which leads to death due to right heart failure. The expression of Nicotinamide phosphoribosyltransferase (Nampt) is increased in the lungs and isolated PAECs of PAH patients. Inhibition of NAMPT is protective in preclinical models of pulmonary hypertension. NAMPT regulates multiple mitochondrial processes that control cell proliferation and survival. Using rodent models of PH, we demonstrated that the mitochondrial unfolded protein response (UPRmt) promotes vascular remodeling. Hence we, hypothesized that NAMPT activates the UPRmt to promote abnormal pulmonary arterial endothelial cell proliferation. Analysis of PAECs isolated from PAH patients show increased expression of the UPRmt pathway mediators, ATF-5, mtHSP70 and ClpP. Human PAEC cell lines were exposed to recombinant Nampt or transduced with lentiviral-Nampt. We observed increased phosphorylation and activation of eIF2 which permits preferential translation of the ATF-5 transcription factor. ATF-5 expression and nuclear localization was increased. Further, we observed increased expression of ATF-5 target genes, mtHSP70, HSP60, ClpP and LonP1 as well as increased PAEC proliferation. Blocking mtHSP70 function reversed the Nampt induced increase in proliferation. Neither UPRmt activation nor proliferation was increased in the presence of enzymatically inactive-Nampt. Our observations demonstrate that Nampt can promote PAEC proliferation by activating the UPRmt and uncovers novel potential targets to address vascular remodeling in PAH.

cell biology↗

bioRxiv2025

Pulmonary Hypertension Promotes Neuroinflammation and Neurodegeneration

IntroductionPulmonary arterial hypertension (PAH) is associated with neurocognitive deficits and abnormal brain MRI. Little is known about the mechanisms underlying these clinical observations. TDP-43 is a proteinopathy associated with frontotemporal lobar degeneration (FTLD), Alzheimers Disease, and Amyotrophic Lateral Sclerosis (ALS). In this study, we hypothesize PAH will result in gliosis, reduced neuronal density, and increased TDP-43 mislocalization. MethodsSprague Dawley rats were randomly assigned to receive Vehicle (DMSO) Monocrotaline, or Sugen/Hypoxia to induce PH. Right heart catheterization was used to confirm PAH. Brain tissue was fixed and probed for microglia (Iba1), astrocytes (GFAP), neurons (NeuN), and TDP-43. Human PH vs control brain tissue was also probed for NeuN and TDP-43. Results and ConclusionsWe identify an increase in microglia and astrocyte density in the frontal cortex along with reduced neuronal density and neuronal TDP-43 mislocalization in rat models of PH. In addition, human PH frontal cortex demonstrated neuronal TDP-43 mislocalization. This is the first evidence of TDP-43 proteinopathy in PH.

physiology↗

bioRxiv2025

The mitochondrial unfolded protein response and metabolic reprogramming promote PASMC proliferation in response to sphingosine kinase-1/sphingosine-1-phosphate signaling

Proliferation and vasoconstriction of the intimal smooth muscle layer of the pulmonary artery are pathogenic characteristics of pulmonary arterial hypertension (PAH). Altered mitochondrial function, i.e. glycolysis, ROS generation and fission, are known potentiators of vascular remodeling. However, most current therapeutic interventions fail to effectively address the proliferation of the pulmonary artery smooth muscle cells (PASMCSs) lining the pulmonary vasculature and highlight the importance of identifying novel pathways to target for intervention. The Sphk1/S1P/S1P2 signaling axis is upregulated in PAH patients and is known to induce PASMC proliferation during hypoxia-mediated pulmonary hypertension (HPH). Interestingly, Sphk1 modulates mitochondrial function in that it regulates dynamics, cell growth and survival and in C. elegans, it induces activation of the unfolded protein response (UPRmt). We aimed to investigate if the Sphk1/S1P/S1P2 signaling axis promotes vascular remodeling in PAH via activation of the UPRmt. PASMCs isolated from IPAH patients were subjected to RNAseq analysis. The effect of Sphk1 or S1P was interrogated in hPASMC cell lines and the HPH model was used to assess the effect of the UPRmt on PAH pathogenesis. RNAseq analysis revealed that pathways involved in mitochondrial respiration were among the top 20 most significantly regulated pathways. Furthermore, ATF-5, the transcription factor that mediates the UPRmt was significantly upregulated. In hPASMCs, Sphk1/S1P lead to decreased respiration, increased glycolysis, fission, ROS and UPRmt activation. Pharmacological inhibition of the UPRmt mediator, mtHSP70, mitigated the Sphk1 induced increase in hPASMC proliferation. Furthermore, mtHSP70 inhibition was protective in hypoxia-mediated pulmonary hypertension (HPH) as we observed a decrease in right ventricular systolic pressure, right ventricular hypertrophy and vascular remodeling. These data suggest that the UPRmt promotes vascular remodeling in PAH and may present a novel pathway to target for pharmaceutical intervention.

cell biology↗