Chronic PARP-1 inhibition reduces carotid vessel remodeling and oxidative damage of the dorsal hippocampus in spontaneously hypertensive rats.

Vascular remodeling during chronic hypertension may impair the supply of tissues with oxygen, glucose and other compounds, potentially unleashing deleterious effects. In this study, we used Spontaneously Hypertensive Rats and normotensive Wistar-Kyoto rats with or without pharmacological inhibition of poly(ADP-ribose)polymerase-1 by an experimental compound L-2286, to evaluate carotid artery remodeling and consequent damage of neuronal tissue during hypertension. We observed elevated oxidative stress and profound thickening of the vascular wall with fibrotic tissue accumulation induced by elevated blood pressure. 32 weeks of L-2286 treatment attenuated these processes by modulating mitogen activated protein kinase phosphatase-1 cellular levels in carotid arteries. In hypertensive animals, vascular inflammation and endothelial dysfunction was observed by NF-κB nuclear accumulation and impaired vasodilation to acetylcholine, respectively. Pharmacological poly(ADP-ribose)polymerase-1 inhibition interfered in these processes and mitigated Apoptosis Inducing Factor dependent cell death events, thus improved structural and functional alterations of carotid arteries, without affecting blood pressure. Chronic poly(ADP-ribose)polymerase-1 inhibition protected neuronal tissue against oxidative damage, assessed by nitrotyrosine, 4-hydroxinonenal and 8-oxoguanosine immunohistochemistry in the area of Cornu ammonis 1 of the dorsal hippocampus in hypertensive rats. In this area, extensive pyramidal cell loss was also attenuated by treatment with lowered poly(ADP-ribose)polymer formation. It also preserved the structure of fissural arteries and attenuated perivascular white matter lesions and reactive astrogliosis in hypertensive rats. These data support the premise in which chronic poly(ADP-ribose)polymerase-1 inhibition has beneficial effects on hypertension related tissue damage both in vascular tissue and in the hippocampus by altering signaling events, reducing oxidative/nitrosative stress and inflammatory status, without lowering blood pressure

L-2286 treatment attenuated structural and functional remodeling of carotid arteries, without affecting SBP.

<p>(A) SBP of animals, measured every 4 weeks during the treatment period. (B) IMT of carotid arteries measured by ultrasound imaging at the beginning and at the end of the study. (C, D) Relaxation properties of isolated carotid artery rings against 60 mM KCl pre-contraction, in the presence of cumulative doses of (C) ACh and (D) SNP. (E) Representative micrographs of immunostaining for NT accumulation in carotid arteries (scale bar 30 μm). (F) Representative Masson’s trichrome stained micrographs (scale bar 30 μm) and quantification of (G) collagen accumulation in carotid artery walls. Data are presented as mean±S.E.M. ^#p<0.05, ^##p<0.01 vs. WKY-C; *p<0.05, **p<0.01 vs. respective controls.</p

Representative micrographs of fluorescent staining for AIF and NF-kB cellular distribution and MKP-1 expression.

<p>(A-D) Nuclear translocation of AIF in carotid artery walls of (A) WKY-C, (B) WKY-L, (C) SHR-C and (D) SHR-L animals (scale bar: 10 μm). (E-F) Cellular level of MKP-1 in (E) WKY-C, (F) WKY-L, (G) SHR-C and (H) SHR-L animals (scale bar: 25 μm). (I-L) Subcellular distribution of NF-kB in (I) WKY-C, (J) WKY-L, (K) SHR-C and (L) SHR-L animals (scale bar: 10 μm).</p

Pharmacological PARP-1 inhibition attenuated oxidative damage and cell loss in dorsal hippocampus.

<p>(A) PAS staining to evaluate structural alterations of the dorsal hippocampus and fissural vessels. *: Lateral cerebral ventriculus (scale bar: 200 μm). (B) NT and (C) HNE staining of CA1 regions for the evaluation of nitrosative damage and lipid peroxidation of pyramidal neurons in the dorsal hippocampus (scale bar 50 μm). (D) Representative micrographs of CA1 region of the dorsal hippocampus with Cresyl violet staining (scale bar 50 μm). (E) Pyramidal neuron number in the CA1 region of dorsal hippocampus. (F-H) Representative micrographs of immunostaining for (F) 8-oxG, (G) PAR and (H) GFAP (scale bar 50 μm) «: perivascular white matter damage. (I) TUNEL positive neurons and (J) numbers relative to pyramidal cells in the CA1 region of dorsal hippocampus (scale bar 50 μm). (F-H) ► points to positively stained cell. Data are presented as mean±S.E.M. ##p<0.01 vs. WKY-C; *p<0.05, **p<0.01 vs. SHRC.</p