Biology subjects

Chandakkar, P.

Publications and source records attributed to Chandakkar, P..

4 recordsLinked to original sources

bioRxiv2019

Sirolimus plus nintedanib treats vascular pathology in HHT mouse models

Hereditary hemorrhagic telangiectasia (HHT), a genetic bleeding disorder leading to systemic arteriovenous malformations (AVMs), is caused by loss-of-function mutations in the ALK1-ENG-Smad1/5/8 pathway. Evidence suggests that HHT pathogenesis strongly relies on overactivated PI3K-Akt-mTOR and VEGFR2 pathways in endothelial cells (ECs). In the BMP9/10-immunoblocked (BMP9/10ib) neonatal mouse model of HHT, we report here that the mTOR inhibitor, sirolimus, and the receptor tyrosine-kinase inhibitor, nintedanib, could synergistically fully block, but also reversed, retinal AVMs to avert retinal bleeding and anemia. Sirolimus plus nintedanib prevented vascular pathology in the oral mucosa, lungs, and liver of the BMP9/10ib mice, as well as significantly reduced gastrointestinal bleeding and anemia in inducible ALK1-deficient adult mice. Mechanistically, in vivo in BMP9/10ib mouse ECs, sirolimus and nintedanib blocked the overactivation of mTOR and VEGFR2, respectively. Furthermore, we found that sirolimus activated ALK2-mediated Smad1/5/8 signaling in primary ECs--including in HHT patient blood outgrowth ECs--and partially rescued Smad1/5/8 activity in vivo in BMP9/10ib mouse ECs. These data demonstrate that the combined correction of endothelial Smad1/5/8, mTOR, and VEGFR2 pathways opposes HHT pathogenesis. Repurposing of sirolimus plus nintedanib might provide therapeutic benefit in HHT patients.

cell biology↗

bioRxiv2017

Tacrolimus Rescues Endothelial ALK1 Loss-Of-Function Signaling And Improves HHT Vascular Pathology

Hereditary hemorrhagic telangiectasia (HHT) is a genetic vascular disorder arising from endothelial cell (EC) proliferation and hypervascularization, for which no cure exists. Because HHT is caused by loss-of-function mutations in BMP9-ALK1-Smad1/5/8 signaling, interventions aimed at activating this pathway are of therapeutic value. By screening FDA-approved drug libraries, we identified tacrolimus (FK-506) as a potent activator of Smad1/5/8 in BMP9-challenged reporter cells. In primary ECs, tacrolimus activated Smad1/5/8 to oppose the pro-angiogenic gene expression signature associated with ALK1 loss-of-function, by notably reducing Dll4 expression. In these cells, tacrolimus also inhibited Akt and p38 stimulation by VEGF. In the BMP9/10-immunodepleted postnatal retina--a mouse model of HHT vascular pathology--tacrolimus activated endothelial Smad1/5/8 and prevented the Dll4 overexpression and hypervascularization associated with this model. Finally, tacrolimus stimulated Smad1/5/8 in cells transfected with BMP9-unresponsive ALK1 HHT mutants and in HHT patient blood outgrowth ECs. We propose that tacrolimus repurposing has therapeutic potential in HHT.

cell biology↗

bioRxiv2016

A modification-specific peptide-based immunization approach using CRM197 carrier protein: Development of a selective vaccine against pyroglutamate Aβ peptides

Strategies aimed at reducing cerebral accumulation of the amyloid-{beta} (A{beta}) peptides have therapeutic potential in Alzheimers disease (AD). A{beta} immunization has proven to be effective at promoting A{beta} clearance in animal models but adverse effects have hampered its clinical evaluation. The first anti-A{beta} immunization clinical trial, which assessed a full-length A{beta}1-42 vaccine, increased the risk of encephalitis most likely because of autoimmune pro-inflammatory T helper 1 (Th1) response against all forms of A{beta}. Immunization against less abundant but potentially more pathologically relevant A{beta} products, such as N-terminally-truncated pyroglutamate-3 A{beta} (A{beta}pE3), could provide efficacy and improve tolerability in A{beta} immunotherapy. Here, we describe a selective vaccine against A{beta}pE3 using the diphtheria toxin mutant CRM197 as carrier protein for epitope presentation. CRM197 is currently used in licensed vaccines and has demonstrated excellent immunogenicity and safety in humans. In mice, our A{beta}pE3:CRM197 vaccine triggered the production of specific anti-A{beta}pE3 antibodies that did not cross-react with A{beta}1-42, non-cyclized A{beta}E3, or N-terminally-truncated pyroglutamate-11 A{beta} (A{beta}pE11). A{beta}pE3:CRM197 antiserum strongly labeled A{beta}pE3 in insoluble protein extracts and decorated cortical amyloid plaques in human AD brains. Anti-A{beta}pE3 antibodies were almost exclusively of the IgG1 isotype, suggesting an anti-inflammatory Th2 response bias to the A{beta}pE3:CRM197 vaccine. To the best of our knowledge, this study shows for the first time that CRM197 has potential as a safe and suitable vaccine carrier for active and selective immunization against specific protein sequence modifications or conformations, such as A{beta}pE3.

neuroscience↗

bioRxiv2016

A mouse model of hereditary hemorrhagic telangiectasia generated by transmammary-delivered immunoblocking of BMP9 and BMP10

Hereditary hemorrhagic telangiectasia (HHT) is a potentially life-threatening genetic vascular disorder caused by loss-of-function mutations in the genes encoding activin receptor-like kinase 1 (ALK1), endoglin, Smad4, and bone morphogenetic protein 9 (BMP9). Injections of mouse neonates with BMP9/10 blocking antibodies lead to HHT-like vascular defects in the postnatal retinal angiogenesis model. Mothers and newborns share the same immunity through the transfer of maternal antibodies during breastfeeding. Here, we investigated whether the transmammary delivery route could improve the ease and consistency of administering anti-BMP9/10 antibodies in the postnatal retinal angiogenesis model. We found that anti-BMP9/10 antibodies, when intraperitoneally injected into lactating dams, are efficiently transferred into the circulation of breastfed neonatal pups. Strikingly, pups receiving anti-BMP9/10 antibodies via breastfeeding displayed consistent and robust vascular pathology in the retina, which included hypervascularization and defects in arteriovenous specification, as well as the presence of multiple and massive arteriovenous malformations. Furthermore, RNA-Seq analyses of neonatal retinas identified an increase in the key pro-angiogenic factor, angiopoietin-2, as the most significant change in gene expression triggered by the transmammary delivery of anti-BMP9/10 antibodies. Transmammary-delivered BMP9/10 immunoblocking in the mouse neonatal retina is therefore a practical, noninvasive, reliable, and robust model of HHT vascular pathology.

cell biology↗