Angom, Ramcharan Singh

PLEXIND1 is upregulated in several cancers, including pancreatic ductal adenocarcinoma (PDAC). It is an established mediator of semaphorin signaling, and neuropilins are its known coreceptors. Herein, we report data to support the proposal that PLEXIND1 acts as a transforming growth factor beta (TGFβ) coreceptor, modulating cell growth through SMAD3 signaling. Our findings demonstrate that PLEXIND1 plays a pro-tumorigenic role in PDAC cells with oncogenic KRAS (KRASmut). We show in KRASmut PDAC cell lines (PANC-1, AsPC-1,4535) PLEXIND1 downregulation results in decreased cell viability (in vitro) and reduced tumor growth (in vivo). Conversely, PLEXIND1 acts as a tumor suppressor in the PDAC cell line (BxPC-3) with wild-type KRAS (KRASwt), as its reduced expression results in higher cell viability (in-vitro) and tumor growth (in vivo). Additionally, we demonstrate that PLEXIND1-mediated interactions can be selectively disrupted using a peptide based on its C-terminal sequence (a PDZ domain-binding motif), an outcome that may possess significant therapeutic implications. To our knowledge, this is the first report showing that (1) PLEXIND1 acts as a TGFβ coreceptor and mediates SMAD3 signaling, and (2) differential roles of PLEXIND1 in PDAC cell lines correlate with KRASmut and KRASwt status.

Vascular endothelial growth factor A (VEGF) signals primarily through its cognate receptor VEGFR-2 to control vasculogenesis and angiogenesis. Dysregulation of these physiological processes contributes to the pathologies of heart disease, stroke, and cancer. Protein kinase D (PKD) plays a crucial role in the regulation of angiogenesis by modulating endothelial cell proliferation and migration. In human umbilical vein endothelial cells (HUVEC) and human blood outgrowth endothelial cells (BOEC), knockdown of PKD-1 or PKD-2 downregulates VEGFR-2 and significantly inhibits VEGF-induced endothelial cell proliferation and migration. We sought to determine the molecular mechanism through which PKD modulates VEGFR-2 expression. Based on bioinformatics data, activating enhancer binding protein 2 (AP2) binding sites exist within the VEGFR-2 promoter. Thus, we hypothesized PKD may downregulate VEGFR-2 through AP2-mediated transcriptional repression of the VEGFR-2 promoter. Indeed, AP2β binds the VEGFR-2 promoter upon PKD knockdown in HUVEC as evident by chromatin immunoprecipitation assay. Luciferase reporter assays using serial deletions of AP2β binding sites within the VEGFR-2 promoter revealed transcriptional activity negatively correlated with the number of AP2β binding sites, thus confirming negative regulation of VEGFR-2 transcription by AP2β. Next, using siRNA, we demonstrated that upregulation of AP2β decreased VEGFR-2 expression and loss of AP2β enhanced VEGFR-2 expression. In vivo studies confirmed this finding as we observed increased VEGFR-2 immunostaining in the dorsal horn of the spinal cord of embryonic day 13 AP2β knockout mice. We hypothesize that PKD directly regulates AP2β function by serine phosphorylation and ongoing studies are being conducted to determine phosphorylation sites in AP2β directly regulated by PKD. Taken together, we demonstrate AP2β negatively regulates VEGFR-2 transcription and VEGFR-2 is a major downstream target of PKD. Our findings describing how PKD regulates angiogenesis may contribute to the development of therapies to improve the clinical outcome of patients afflicted by heart disease, stroke, and cancer.

AbstractExtracellular vesicles are endogenous biological nanoparticles that have potential for use as therapeutic nanoparticles or as delivery vehicles for therapeutic agents. Milk nanovesicles (MNV) are extracellular vesicles isolated from bovine milk that have been explored for use as delivery vehicles for RNA therapeutics such as small interfering RNA (siRNA). We performed in vivo toxicological studies of MNV or therapeutic MNV (tMNV) loaded with siRNA as a prelude to their clinical use. Development toxicity was assessed in zebrafish embryos. Acute toxicity was assessed in both mice and zebrafish whereas safety, biochemical, histological and immune effects after multiple dosing were assessed in mice. Zebrafish embryo hatching was accelerated with MNV and tMNV. While acute toxicity or effects on mortality were not observed in zebrafish, developmental effects were observed at high concentrations of MNV. There was a lack of discernable toxicity, mortality and systemic inflammatory or immunological responses in mice following administration of either MNVs or tMNVs. The tolerability and lack of discernable developmental or systemic in vivo toxicity support their use as biological nano‐therapeutics. Adoption of a standardized protocol for systematic analysis of in vivo safety and toxicity will facilitate preclinical assessment of EV based formulations for therapeutic use.

ABSTRACT Aggregated amyloid β (Aβ) peptides in the Alzheimer's disease (AD) brain are hypothesized to trigger several downstream pathologies, including cerebrovascular dysfunction. Previous studies have shown that Aβ peptides can have antiangiogenic properties, which may contribute to vascular dysfunction in the early stages of the disease process. We have generated data showing that brain endothelial cells (ECs) exposed to toxic Aβ1‐42 oligomers can readily enter a senescence phenotype. To determine the effect of Aβ oligomers on brain ECs, we treated early passaged human brain microvascular ECs and HUVECs with high MW Aβ1‐42 oligomers (5 µM, for 72 h). For controls, we used no peptide treatment, 5 µM Aβ1‐42 monomers, and 5 µM Aβ1‐42 fibrils, respectively. Brain ECs treated with Aβ1‐42 oligomers showed increased senescence‐associated β‐galactosidase staining and increased senescence‐associated p21/ p53 expression. Treatment with either Aβ1‐42 monomer or Aβ1‐42 fibrils did not induce senescence in this assay. We then measured vascular endothelial growth factor receptor (VEGFR) expression in the Aβ1‐42 oligomer‐treated ECs, and these cells showed significantly increased VEGFR‐1 expression and decreased VEGFR‐2 levels. Overexpression of VEGFR‐1 in brain ECs readily induced senescence, suggesting a direct role of VEGFR‐1 signaling events in this paradigm. More importantly, small interfering RNA‐mediated knockdown of VEGFR‐1 expression in brain ECs was able to prevent up‐regulation of p21 protein expression and significantly reduced induction of senescence following Aβ1‐42 oligomer treatment. Our studies show that exposure to Aβ1‐42 oligomers may impair vascular functions by altering VEGFR‐1 expression and causing ECs to enter a senescent phenotype. Altered VEGFR expression has been documented in brains of AD patients and suggests that this pathway may play a role in AD disease pathogenesis. These studies suggest that modulating VEGFR‐1 expression and signaling events could potentially prevent senescence and rejuvenate EC functions, and provides us with a novel target to pursue for prevention and treatment of cerebrovascular dysfunction in AD.—Angom, R. S., Wang, Y., Wang, E., Pal, K., Bhattacharya, S., Watzlawik, J. O., Rosenberry, T. L., Das, P., Mukhopadhyay, D. VEGF receptor‐1 modulates amyloid β 1–42 oligomer‐induced senescence in brain endothelial cells. FASEB J. 33, 4626–4637 (2019). www.fasebj.org

ABSTRACT Inflammatory response of blood–brain barrier (BBB) endothelial cells plays an important role in pathogenesis of many central nervous system inflammatory diseases, including multiple sclerosis; however, the molecular mechanism mediating BBB endothelial cell inflammatory response remains unclear. In this study, we first observed that knockdown of neuropilin-1 (NRP1), a co-receptor of several structurally diverse ligands, suppressed interferon-γ (IFNγ)-induced C-X-C motif chemokine 10 expression and activation of STAT1 in brain microvascular endothelial cells in a Rac1-dependent manner. Moreover, endothelial-specific NRP1-knockout mice, VECadherin-Cre-ERT2/NRP1flox/flox mice, showed attenuated disease progression during experimental autoimmune encephalomyelitis, a mouse neuroinflammatory disease model. Detailed analysis utilizing histological staining, quantitative PCR, flow cytometry and magnetic resonance imaging demonstrated that deletion of endothelial NRP1 suppressed neuron demyelination, altered lymphocyte infiltration, preserved BBB function and decreased activation of the STAT1–CXCL10 pathway. Furthermore, increased expression of NRP1 was observed in endothelial cells of acute multiple sclerosis lesions. Our data identify a new molecular mechanism of brain microvascular endothelial inflammatory response through NRP1–IFNγ crosstalk that could be a potential target for intervention of endothelial cell dysfunction in neuroinflammatory diseases.