title: Chronic cerebral hypoperfusion-induced impairment of Aβ clearance requires HB-EGF-dependent sequential activation of HIF1α and MMP9.
abstract: Chronic cerebral hypoperfusion (CCH) manifests Alzheimer's Disease (AD) neuropathology, marked by increased amyloid beta (Aβ). Besides, hypoxia stimulates Heparin-binding EGF-like growth factor (HB-EGF) mRNA expression in the hippocampus. However, involvement of HB-EGF in CCH-induced Aβ pathology remains unidentified. Here, using Bilateral Common Carotid Artery Occlusion mouse model, we explored the mechanism of HB-EGF regulated Aβ induction in CCH. We found that HB-EGF inhibition suppressed, while exogenous-HB-EGF triggered hippocampal Aβ, proving HB-EGF-dependent Aβ increase. We also detected that HB-EGF affected the expression of primary Aβ transporters, receptor for advanced glycation end-products (RAGE) and lipoprotein receptor-related protein-1 (LRP-1), indicating impaired Aβ clearance across the blood-brain barrier (BBB). An HB-EGF-dependent loss in BBB integrity supported impaired Aβ clearance. The effect of HB-EGF on Amyloid Precursor Protein pathway was relatively insignificant, suggesting a lesser effect on Aβ generation. Delving into BBB disruption mechanism demonstrated HB-EGF-mediated stimulation of Matrix metalloprotease-9 (MMP9), which affected BBB via HB-EGF-ectodomain shedding and epidermal growth factor receptor activation. Examining the intersection of HB-EGF-regulated pathway and hypoxia revealed HB-EGF-dependent increase in transcription factor, Hypoxia-inducible factor-1alpha (HIF1α). Further, via binding to hypoxia-responsive elements in MMP9 gene, HIF1α stimulated MMP9 expression, and therefore appeared as a prominent intermediary in HB-EGF-induced BBB damage. Overall, our study reveals the essential role of HB-EGF in triggering CCH-mediated Aβ accumulation. The proposed mechanism involves an HB-EGF-dependent HIF1α increase, generating MMP9 that stimulates soluble-HB-EGF/EGFR-induced BBB disintegration. Consequently, CCH-mediated hippocampal RAGE and LRP-1 deregulation together with BBB damage impair Aβ transport and clearance where HB-EGF plays a pivotal role.
authors.affiliation: Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR campus, Lucknow, India; Developmental Toxicology Laboratory, System Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan, 31, Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India.
authors.forename: Anushruti
authors.initials: A
authors.lastname: Ashok
authors.affiliation: Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR campus, Lucknow, India; Developmental Toxicology Laboratory, System Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan, 31, Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India.
authors.forename: Nagendra Kumar
authors.initials: NK
authors.lastname: Rai
authors.affiliation: Developmental Toxicology Laboratory, System Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan, 31, Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India.
authors.forename: Waseem
authors.initials: W
authors.lastname: Raza
authors.affiliation: Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR campus, Lucknow, India; Developmental Toxicology Laboratory, System Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan, 31, Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India.
authors.forename: Rukmani
authors.initials: R
authors.lastname: Pandey
authors.affiliation: Academy of Scientific and Innovative Research (AcSIR), CSIR-IITR campus, Lucknow, India; Developmental Toxicology Laboratory, System Toxicology and Health Risk Assessment Group, CSIR-Indian Institute of Toxicology Research (CSIR-IITR), Vishvigyan Bhavan, 31, Mahatma Gandhi Marg, Lucknow 226001, Uttar Pradesh, India. Electronic address: sanghmitra@iitr.res.in.
authors.forename: Sanghamitra
authors.initials: S
authors.lastname: Bandyopadhyay
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002545:Brain Ischemia / Q000378:metabolism; D004195:Disease Models, Animal; D005786:Gene Expression Regulation / Q000502:physiology; D066257:Heparin-binding EGF-like Growth Factor / Q000235:genetics / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D051379:Mice; D010477:Perfusion; D000067759:Receptor for Advanced Glycation End Products / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D066257:Heparin-binding EGF-like Growth Factor; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D000067759:Receptor for Advanced Glycation End Products; D020780:Matrix Metalloproteinase 9; C501830:Mmp9 protein, mouse
keywords: AD; BBB; BCCAO; HB-EGF; LRP-1; RAGE