Dawid Walas

Cep126 is required for pericentriolar satellite localisation to the centrosome and for primary cilium formation

The centrosome is the primary microtubule‐organising centre of animal cells and it has crucial roles in several fundamental cellular functions, including cell division, cell polarity, and intracellular transport. The mechanisms responsible for this are not completely understood.

Systemic leukotriene B4 receptor antagonism lowers arterial blood pressure and improves autonomic function in the spontaneously hypertensive rat

Evidence indicates an association between hypertension and chronic systemic inflammation in both human hypertension and experimental animal models. Previous studies in the spontaneously hypertensive rat (SHR) support a role for leukotriene B4 (LTB4), a potent chemoattractant involved in the inflammatory response, but its mode of action is poorly understood. In the SHR, we observed an increase in T cells and macrophages in the brainstem; in addition, gene expression profiling data showed that LTB4 production, degradation and downstream signalling in the brainstem of the SHR are dynamically regulated during hypertension. When LTB4 receptor 1 (BLT1) receptors were blocked with CP‐105,696, arterial pressure was reduced in the SHR compared to the normotensive control and this reduction was associated with a significant decrease in systolic blood pressure (BP) indicators. These data provide new evidence for the role of LTB4 as an important neuro‐immune pathway in the development of hypertension and therefore may serve as a novel therapeutic target for the treatment of neurogenic hypertension.

Differences in autonomic innervation to the vertebrobasilar arteries in spontaneously hypertensive and Wistar rats

Essential hypertension is associated with hyperactivity of the sympathetic nervous system and hypoperfusion of the brainstem area controlling arterial pressure. Sympathetic and parasympathetic innervation of vertebrobasilar arteries may regulate blood perfusion to the brainstem. We examined the autonomic innervation of these arteries in pre‐hypertensive (PHSH) and hypertensive spontaneously hypertensive (SH) rats relative to age‐matched Wistar rats. Our main findings were: (1) an unexpected decrease in noradrenergic sympathetic innervation in PHSH and SH compared to Wistar rats despite elevated sympathetic drive in PHSH rats; (2) a dramatic deficit in cholinergic and peptidergic parasympathetic innervation in PHSH and SH compared to Wistar rats; and (3) denervation of sympathetic fibres did not alter vertebrobasilar artery morphology or arterial pressure. Our results support a compromised vasodilatory capacity in PHSH and SH rats compared to Wistar rats, which may explain their hypoperfused brainstem.

OS 11-05 Superior cervical ganglionectomy (SCGx) reduces sympathetic innervation of vertebrobasilar arteries but does not affect cerebrovascular remodelling in the adult spontaneously hypertensive rat (SHR).

Objective: Our hypothesis is that hypoperfusion of the brainstem is due to elevated vertebrobasilar artery resistance, triggers hypertension. We asked: is there a functional relationship between the sympathetic innervation to the vertebrobasilar system and its remodelling in the SHR? Design and Method: SHRs (11–12 weeks old) received either sham surgery or bilateral SCGx. Animals recovered for 14 days, were then perfused-fixed with 4% PFA and the vertebrobasilar arteries examined using both immunohistofluorecent staining of sympathetic (anti-D&bgr;H) and parasympathetic (anti-VAChT) fibres, and by cross sectional examination of vertebral and basilar arteries. Results: Bilateral SCGx reduced sympathetic innervation to all parts of basilar artery: anterior (SCGx 123 ± 35 vs sham 198 ± 77 fibres/mm2, p < 0.05), middle (86 ± 17 vs 204 ± 62 fibres/mm2, p < 0.001) and posterior (126 ± 29 vs 291 ± 73 fibres/mm2, p < 0.001) as well as both left (L) and right (R) vertebral arteries (VA, LVA 90 ± 33 vs 232 ± 67 fibres/mm2, p < 0.01 and RVA 88 ± 30 vs 238 ± 66 fibres/mm2, p < 0.01). The parasympathetic innervation to the vertebrobasilar arteries was unchanged after SCGx. Despite the reduction of sympathetic input there was no change to vertebrobasilar artery remodelling: the vessels’ external diameter, lumen size and wall thickness were unaffected by the SCGx. Conclusions: The SCG provides a major innervation to the vertebrobasilar arteries in the SHR but it is not the only source of sympathetic innervation. Reduction of sympathetic input to the vertebrobasilar arteries in SHR with established hypertension does not attenuate cerebrovascular remodelling at least over a 14 day period. Acknowledgements – Wellcome Trust, British Heart Foundation

Os 11-04 Impact of gonadectomy on sympatho-vagal balance in male and female normotensive rat

Objective: It is well established that autonomic nervous system and sympatho-vagal balance plays an important role in maintaining arterial blood pressure (ABP) (Salman IM., 2016) and that autonomic regulation of ABP differs between males and females (Hart EC et al., 2014). We hypothesised that sex hormones affect blood pressure via the autonomic nervous system and that the late development of hypertension in females is due to protective effects of ovarian steroids in females rather than due to detrimental effects of testosterone in males. Design and Method: We used adult, 12 months old, Wistar female and male, intact and gonadectomised rats (n = 8, per each group). Resting ABP was recorded by radio-telemetry. Heart rate (HR) and ABP variability were calculated using Spike2 software. Effect of gender and gonadectomy were assessed by two-way Anova. Results: Females had lower systolic (S)BP compared to males (121 ± 1 vs 128 ± 2 mmHg; P < 0.05). Intact (81 ± 2 mmHg) but not ovariectomised (89 ± 2 mmHg) females had lower diastolic (D)BP compared to males (91 ± 1 mmHg; P < 0.01). Moreover, intact (353 ± 6bpm) but not ovariectomised (307 ± 5 bpm) females had higher HR compared to males (353 ± 6bpm; P < 0.001). However, ovariectomy did not influence the higher respiratory rate in females vs males (91 ± 3 vs 78 ± 3 bpm; P < 0.001). Power spectra analysis of SBP shows that males (22.4 ± 3) and ovariectomised females (26.9 ± 3) had lower High Frequency percentage vs females (38 ± 3; P < 0.05) suggesting that female hormones affect ABP by modulating the parasympathetic activity. The Very Low Frequency percentage was higher in males vs females (40 ± 4 vs 28 ± 4; P < 0.05) suggesting that sympathetic vasomotor tone might play an important role in the differential regulation of SBP between males and females. Conclusions: Altogether, this results show that female hormones have a positive effect on ABP and that they affect ABP via modulating parasympathetic activity. Further analyses of BP and HR variability at different ages are needed to determine the interaction between age, BP and gender.

ISH NIA OS-06 PUTATIVE MECHANISMS FOR CEREBROVASCULAR REMODELLING IN THE SPONTANEOUSLY HYPERTENSIVE RAT (SHR) USING TRANSCRIPTOMICS.

Objective: Cerebrovascular remodeling in the SHR may be causative to the known brainstem hypoperfusion. Using RNA sequencing, we examined age-related processes that may govern remodeling of the cerebral arteries in the SHR. Design and Method: In SHR and their progenitor (normotensive) control (Wistar Kyoto, WKY), RNA-seq was performed at three ages: 5, 9, 13 weeks old. Cerebral arteries were flushed and peeled off the brain, stripped of meninges, snap frozen and RNA extracted. Ilumina platform, Ingenuity Pathway Analysis, histological examination of 5 weeks old basilar arteries by picrosirius red as well as second harmonics generation (SHG) microscopy were used. Results: In the 5, 9 and 13 week old SHR, we identified 16, 10 and 17 pathways that were altered relative to WKY rats, respectively (p < 0.05), two were common at all age groups: fibrosis and antigen presentation. Pathways affected most at the pre-hypertensive age were those involved in the immune system (Graft-vs-Host, OX40, atherosclerosis, autoimmune thyroid disease signalling, dendritic cell maturation, and antigen presentation pathway). There was a marked increase of mRNA levels of several collagen subunits: col4&agr;1, col6&agr;2, col8&agr;1, col9&agr;2 col11&agr;1, col16&agr;1, col18&agr;1 and col26&agr;1. Based on these results, we hypothesised that altered fibrotic pathways would result in increased collagen content in basilar arteries contributing to their stiffness. Unexpectedly, total collagen type I and III stained with picrosirius red was diminished in 5 week old SHR vs WKY rat in: tunica externa (19% p < 0.01), tunica media (23%, p < 0.001). However, SHG showed increased fibrillogenesis in the tunica externa (F/B ratio 0.27 ± 0.13 vs 0.43 ± 0.3 for SHR and WKY, respectively, p = 0.014), whereas tunica media was unaffected. Conclusions: Remodeling of the cerebral arteries in the SHR may be induced, in part, by inflammation before the onset of hypertension. This triggers alterations in extracellular matrix and in vascular resistance thereby contributing to cerebral hypoperfusion.

PS 04-26 PHARMACOLOGICAL ACTIVATION OF TRPV4 BY GSK1016790A ATTENUATES ARTERIOGENESIS TRIGGERED BY INCREASED SHEAR STRESS

Objective: Arteriogenesis may aid the efforts in lowering vascular resistance and improving organ blood flow if it can be controlled. A previous claim that pharmacological activation of TRPV4 channels using 4&agr;-Phorbol 12,13-didecanoate (4&agr;PDD), a non-selective agonist, enhanced arteriogenesis in the posterior cerebral circulation (Schierling et al., 2011) was examined using a highly selective TRPV4 agonist - GSK1016790A. Design and Method: Increased shear stress in the cerebral circulation was induced by bilateral occlusion of the common carotid arteries (BCL). Sprague-Dawley rats were subjected to either: sham, BCL, BCL+vehicle, BCL+4&agr;PDD, BCL+GSK1016790A. The vehicle and drugs were delivered by osmotic minipump (7 days) into the cerebral circulation via a carotid artery. Brain casts using ink/gelatine contrast medium were examined. Results: BCL increased basilar artery diameter relative to sham (348 ± 14 vs 224 ± 23 &mgr;m, respectively, p < 0.001). The vehicle control did not differ from the BCL (BCL+vehicle 360.2 ± 42.42 &mgr;m). There was a difference between BCL/vehicle and sham control (360 ± 42 vs 224 ± 23 &mgr;m respectively, p < 0.01). The two TRPV4 agonists had an opposite effect on the basilar artery diameter. BCL+4&agr;PDD group had basilar arteries that remodelled to the same extent as the BCL only group (400 ± 51 vs 348 ± 14 &mgr;m, respectively, NS) whereas infusion of GSK1016790A attenuated the remodelling induced by BCL (294 ± 22 vs 348 ± 14 &mgr;m respectively, p < 0.05). A 7 day recovery from GSK1016790A increased basilar artery diameter (407 ± 43 &mgr;m, p < 0.05). Similar findings were apparent in the vertebral arteries also. Conclusions: Activation of TRPV4 channels using a selective agonist attenuates posterior cerebral circulation arteriogenesis triggered by increased shear stress model. Thus, we do not support the contention that TRPV4 channel activity would be a therapeutic target to increase organ blood flow.