Human Middle Meningeal Arteries Research Articles

Differential expression of components of the CGRP-receptor family in human coronary and human middle meningeal arteries: functional implications

BackgroundDifferent responses in human coronary arteries (HCA) and human middle meningeal arteries (HMMA) were observed for some of the novel CGRP receptor antagonists, the gepants, for inhibiting CGRP-induced relaxation. These differences could be explained by the presence of different receptor populations in the two vascular beds. Here, we aim to elucidate which receptors are involved in the relaxation to calcitonin gene-related peptide (CGRP), adrenomedullin (AM) and adrenomedullin 2 (AM2) in HCA and HMMA.MethodsRNA was isolated from homogenized human arteries (23 HCAs; 12 F, 11 M, age 50 ± 3 years and 26 HMMAs; 14 F, 12 M, age 51 ± 3 years) and qPCR was performed for different receptor subunits. Additionally, relaxation responses to CGRP, AM or AM2 of the human arteries were quantified using a Mulvany myograph system, in the presence or absence of the adrenomedullin 1 receptor antagonist AM22-52 and/or olcegepant.ResultsCalcitonin-like receptor (CLR) mRNA was expressed equally in both vascular beds, while calcitonin receptor (CTR) and receptor activity-modifying protein 3 (RAMP3) expression was low and could not be detected in all samples. RAMP1 expression was similar in HCA and HMMA, while RAMP2 expression was higher in HMMA. Moreover, receptor component protein (RCP) expression was higher in HMMA than in HCA. Functional experiments showed that olcegepant inhibits relaxation to all three agonists in both vascular beds. In HCA, antagonist AM22-52 did not inhibit relaxation to any of the agonists, while a trend for blocking relaxation to AM and AM2 could be observed in HMMA.ConclusionBased on the combined results from receptor subunit mRNA expression and the functional responses in both vascular tissues, relaxation of HCA is mainly mediated via the canonical CGRP receptor (CLR-RAMP1), while relaxation of HMMA can be mediated via both the canonical CGRP receptor and the adrenomedullin 1 receptor (CLR-RAMP2). Future research should investigate whether RAMP2 predominance over RAMP1 in the meningeal vasculature results in altered migraine susceptibility or in a different response to anti-migraine medication in these patients. Moreover, the exact role of RCP in CGRP receptor signalling should be elucidated in future research.

Sex differences in CGRP-induced vasodilation of human middle meningeal arteries but not human coronary arteries: implications for migraine.

Migraine prevalence and levels of calcitonin gene-related peptide (CGRP), a peptide involved in migraine pathophysiology, differ between men and women, and appear to be affected by changes in sex hormones. The present study investigated the sex-specific responses to CGRP in human isolated arteries. CGRP-induced relaxation of 62 (28 men and 34 women) human isolated middle meningeal arteries (HMMA) and 139 (69 men and 70 women) human isolated coronary arteries (HCA) was compared between men and women in groups <50 years and ≥50 years of age as a proxy for pre- and postmenopausal status in women, as well as matched-age groups for men. In HCA, no differences were observed between male and female tissue, or between the different age groups. However, in HMMA, the maximum response was significantly smaller and CGRP was less potent in females <50 compared with males <50 years of age. No differences were observed between the older age groups. Sex differences were observed for CGRP-induced relaxation of HMMA, but not HCA. These differences could arise from differential receptor expression in the vascular beds combined with the effect of sex hormones on CGRP and subsequent receptor desensitization.

Pharmacology of erenumab in human isolated coronary and meningeal arteries: Additional effect of gepants on top of a maximum effect of erenumab.

Multiple drugs targeting the calcitonin gene-related peptide (CGRP) receptor have been developed for migraine treatment. Here, the effect of the monoclonal antibody erenumab on CGRP-induced vasorelaxation was investigated in human isolated blood vessels, as well as the effect of combining erenumab with the small molecule drugs, namely rimegepant, olcegepant, or sumatriptan. Concentration-response curves to CGRP, adrenomedullin or pramlintide were constructed in human coronary artery (HCA) and human middle meningeal artery (HMMA) segments, incubated with or without erenumab and/or olcegepant. pA2 or pKb values were calculated to determine the potency of erenumab in both tissues. To study whether acutely acting antimigraine drugs exerted additional CGRP-blocking effects on top of erenumab, HCA segments were incubated with a maximally effective concentration of erenumab (3μM), precontracted with KCl and exposed to CGRP, followed by rimegepant, olcegepant, or sumatriptan in increasing concentrations. Erenumab shifted the concentration-response curve to CGRP in both vascular tissues. However, in HCA, the Schild plot slope was significantly smaller than unity, whereas this was not the case in HMMA, indicating different CGRP receptor mechanisms in these tissues. In HCA, rimegepant, olcegepant and sumatriptan exerted additional effects on CGRP on top of a maximal effect of erenumab. Gepants have additional effects on top of erenumab for CGRP-induced relaxation and could be effective in treating migraine attacks in patients already using erenumab as prophylaxis.

Blocking the CGRP Receptor: Differences across Human Vascular Beds.

Multiple drugs targeting the calcitonin gene-related peptide (CGRP) receptor have been developed for the treatment of migraine. Here, the effect of the small-molecule CGRP receptor antagonist zavegepant (0.1 nM-1 µM) on CGRP-induced relaxation in isolated human coronary arteries (HCAs) was investigated. A Schild plot was constructed and a pA2 value was calculated to determine the potency of zavegepant. The potency and Schild plot slopes of atogepant, olcegepant, rimegepant, telcagepant, ubrogepant and zavegepant in HCAs and human middle meningeal arteries (HMMAs), obtained from our earlier studies, were compared. Zavegepant shifted the concentration-response curve to CGRP in HCAs. The corresponding Schild plot slope was not different from unity, resulting in a pA2 value of 9.92 ± 0.24. No potency difference between HCAs and HMMAs was observed. Interestingly, olcegepant, atogepant and rimegepant, with a Schild plot slope < 1 in HCAs, were all >1 log unit more potent in HMMAs than in HCAs, while telcagepant, ubrogepant and zavegepant, with a Schild plot slope not different from unity, showed similar (<1 log difference) potency across both tissues. As a Schild plot slope < 1 may point to the involvement of multiple receptors, it is important to further identify the receptors involved in the relaxation to CGRP in HCAs, which may be used to improve the cardiovascular safety of future antimigraine drugs.

Characterisation of vasodilatory responses in the presence of the CGRP receptor antibody erenumab in human isolated arteries.

Migraine is associated with activation of the trigeminovascular system, release of calcitonin gene-related peptide (CGRP) and dilation of dural arteries. Novel treatments target calcitonin gene-related peptide or its receptor, which are present in all vascular beds, raising cardiovascular concerns. Erenumab is a human CGRP-receptor antibody approved for the prophylactic treatment of migraine. We characterised the relaxant responses to CGRP in the absence and presence of erenumab (1 μM) in isolated human middle meningeal, internal mammary and (proximal and distal) coronary arteries. Furthermore, in human internal mammary arteries from cardiovascularly-compromised patients, we assessed the pharmacological specificity of erenumab by investigating whether the vasodilatory responses to acetylcholine, sodium nitroprusside, pituitary adenylate cyclase activating polypeptide-38 (PACAP), vasoactive intestinal peptide and nicardipine, along with the vasoconstrictor responses to dihydroergotamine, were modified by erenumab. Calcitonin gene-related peptide induced concentration-dependent vasodilatory responses in all vessels studied that were significantly antagonised by erenumab. In human internal mammary arteries from cardiovascularly-compromised patients, the responses to acetylcholine, sodium nitroprusside, PACAP, vasoactive intestinal peptide, nicardipine and dihydroergotamine were unaffected by erenumab. Erenumab inhibits calcitonin gene-related peptide-induced vasodilatory responses in human middle meningeal arteries, human internal mammary arteries and human coronary arteries. Moreover, erenumab shows functional specificity as no interaction was observed with the relaxant responses to several vasodilators, nor the dihydroergotamine-dependent vasoconstrictor responses.

Exploration of purinergic receptors as potential anti-migraine targets using established pre-clinical migraine models.

The current understanding of mechanisms behind migraine pain has been greatly enhanced with the recent therapies targeting calcitonin gene-related peptide and its receptor. The clinical efficacy of calcitonin gene-related peptide-blocking drugs indicates that, at least in a considerable proportion of patients, calcitonin gene-related peptide is a key molecule in migraine pain. There are several receptors and molecular pathways that can affect the release of and response to calcitonin gene-related peptide. One of these could be purinergic receptors that are involved in nociception, but these are greatly understudied with respect to migraine. We aimed to explore purinergic receptors as potential anti-migraine targets. We used the human middle meningeal artery as a proxy for the trigeminal system to screen for possible anti-migraine candidates. The human findings were followed by intravital microscopy and calcitonin gene-related peptide release measurements in rodents. We show that the purinergic P2Y13 receptor fulfills all the features of a potential anti-migraine target. The P2Y13 receptor is expressed in both the human trigeminal ganglion and middle meningeal artery and activation of this receptor causes: a) middle meningeal artery contraction in vitro; b) reduced dural artery dilation following periarterial electrical stimulation in vivo and c) a reduction of CGRP release from both the dura and the trigeminal ganglion in situ. Furthermore, we show that P2X3 receptor activation of the trigeminal ganglion causes calcitonin gene-related peptide release and middle meningeal artery dilation. Both an agonist directed at the P2Y13 receptor and an antagonist of the P2X3 receptor seem to be viable potential anti-migraine therapies.

Cranioselectivity of Sumatriptan Revisited: Pronounced Contractions to Sumatriptan in Small Human Isolated Coronary Artery

Initial concerns about the coronary side-effect potential of the anti-migraine drug sumatriptan and second-generation triptans initiated cranioselectivity studies using proximal human coronary arteries. However, myocardial ischaemia may originate from both large and small human coronary arteries. We investigated the contractions to sumatriptan in proximal (internal diameter 2-3mm), distal (internal diameter 1,000-1,500μm) and small (internal diameter 500-1,000μm) human epicardial coronary arteries and compared these with contractions in the human middle meningeal artery. Concentration response curves to sumatriptan in human coronary arteries were constructed in the absence or presence of the 5-hydroxytryptamine1B (5-HT1B) receptor antagonist SB224289 and the 5-HT1D receptor antagonist BRL15572. The effect of sumatriptan on increased cyclic adenosine monophosphate (cAMP) levels induced by forskolin in proximal and distal coronary artery segments was investigated using a biochemical assay. Western blotting was used to analyse the 5-HT1B receptor density in the human arteries. Contractions in the proximal human coronary artery were significantly smaller than those in the human meningeal artery, as we showed previously. In contrast, contractions to sumatriptan in distal and small human coronary arteries were not different from those in the human meningeal artery. The 5-HT1B receptor antagonist SB224289, but not the 5-HT1D receptor antagonist BRL15572, inhibited the contraction induced by sumatriptan in the coronary arteries. Moreover, in distal, but not in proximal, coronary arteries, sumatriptan inhibited the increase in cAMP levels induced by forskolin. Contrary to our expectations, the 5-HT1B receptor expression was more pronounced in the proximal human coronary artery than in the distal and small human coronary artery. Based on functional experiments in distal and small human coronary arteries, contractions to sumatriptan are not as cranioselective as previously assumed. However, the vast clinical experience with sumatriptan and other triptans has proven that these drugs are cardiovascularly safe when contraindications are taken into account.

K ATP channels in pig and human intracranial arteries

Clinical trials suggest that synthetic ATP-sensitive K + (K ATP) channel openers may cause headache and migraine by dilating cerebral and meningeal arteries. We studied the mRNA expression profile of K ATP channel subunits in the pig and human middle meningeal artery (MMA) and in the pig middle cerebral artery (MCA). We determined the order of potency of four K ATP channel openers when applied to isolated pig MMA and MCA, and we examined the potential inhibitory effects of the Kir6.1 subunit specific K ATP channel blocker PNU-37883A on K ATP channel opener-induced relaxation of the isolated pig MMA and MCA. Using conventional RT-PCR, we detected the mRNA transcripts of the K ATP channel subunits Kir6.1 and SUR2B in all the examined pig and human intracranial arteries. Application of K ATP channel openers to isolated pig MMA and MCA in myographs caused a concentration-dependent vasodilatation with an order of potency that supports the presence of functional SUR2B K ATP channel subunits. 10 − 7 M PNU-37883A significantly inhibited the in vitro dilatory responses of the potent K ATP channel opener P-1075 in both pig MMA and MCA. In conclusion, our combined mRNA expression and pharmacological studies indicate that Kir6.1/SUR2B is the major functional K ATP channel complex in the pig MMA and MCA, and mRNA expression studies suggest that the human MMA shares this K ATP channel subunit profile. Specific blocking of Kir6.1 or SUR2B K ATP channel subunits in large cerebral and meningeal arteries may be a future anti-migraine strategy.

Magnetic resonance angiography of the human middle meningeal artery: Implications for migraine

To describe a novel noninvasive method for studying middle meningeal artery (MMA) diameter changes in vivo in humans. Dilatation of the MMA has been implicated in the pathophysiology of migraine headache, but no direct evidence has been obtained in humans. The diameter of the MMA (the extracranial part) was measured in 19 healthy volunteers before and after administration of a vasodilator (nitroglycerin (NTG), 1.2 mg sublingually) known to provoke headache. We used magnetic resonance angiography (MRA) in combination with a 47-mm microscopy coil and a semiautomatic contour detection program. The diameter of the MMA was 1.5+/-0.26 mm (mean+/-SD) before and 1.79+/-0.30 mm after NTG administration. This increase was 20.1% (95% CI=12.9-27.3; P<0.001). The mean increase in subjects who developed headache (N=11) was 0.34+/-0.19 mm as compared to 0.22 mm+/-0.20 mm in the eight subjects who did not (95% CI for difference=-0.07 to 0.31; P=0.188). MRA in combination with a 47-mm microscopy coil is a novel, noninvasive method to measure changes in the diameter of human meningeal vessels, with potential applications for migraine and other fields of neurovascular research.

Characterisation of CGRP receptors in the human isolated middle meningeal artery

Although the understanding of migraine pathophysiology is still incomplete, there seems to be little doubt that dilatation of cranial blood vessels, including meningeal arteries, is involved in the headache phase of migraine. Since calcitonin gene-related peptide (CGRP) has been implicated in this vasodilatation, the present study set out to compare the relaxant effects of the endogenous ligand h-αCGRP, and [ethylamide-Cys 2,7]h-αCGRP ([Cys(Et) 2,7]h-αCGRP), a CGRP 2 receptor agonist, on human isolated middle meningeal artery segments, precontracted with KCl. Classical Schild plot analysis was used to characterise the receptor population in this artery using BIBN4096BS and h-αCGRP 8–37 as antagonists. h-αCGRP relaxed arterial segments more potently than [Cys(Et) 2,7]h-αCGRP (pEC 50: 8.51 ± 0.16 and 7.48 ± 0.24, respectively), while the maximal responses to these agonists were not significantly different. BIBN4096BS equipotently blocked the relaxations induced by both agonists with a p A 2 of ∼ 10 and with a Schild plot slope not significantly different from unity. h-αCGRP 8–37 also antagonised the response to h-αCGRP with a p A 2 of 6.46 ± 0.16 and a Schild plot slope not different from unity. Furthermore, the results obtained from RT-PCR studies confirmed the presence of all the essential components required for a functional CGRP 1 receptor in these arteries. Considering the high antagonist potency of BIBN4096BS, coupled to the lower agonist potency of [Cys (Et) 2,7]h-αCGRP, it is reasonable to suggest a predominant role of CGRP 1 receptors in the human middle meningeal artery. This view is reinforced by Schild plot analysis, which revealed a slope of unity in all experiments, giving further evidence for a homogeneous CGRP receptor population in this vascular preparation.

Study of Cgrp-Receptors in Human Isolated Middle Meningeal Arteries Using Bibn4096Bs, Compound 1, and HαCgrp(8-37)

Calcitonin, CGRP, adrenomedullin, and amylin require both CRLR (calcitonin-gene receptor like receptor) and receptor activity modifying proteins (RAMP1, RAMP2, and RAMP3) in different combinations for expression of selective, functional receptors[1]. We investigated whether the antagonists BIBN4096BS[2], Compound 1 (WO98/11128, [3]), and CGRP(8-37) are functionally selective for CGRP receptors in human middle meningeal arteries (HMMA).

Craniovascular selectivity of eletriptan and sumatriptan in human isolated blood vessels.

Eletriptan is a 5-HT(1B/1D) receptor agonist with proven efficacy in the acute treatment of migraine. To assess the craniovascular selectivity of eletriptan and sumatriptan in blood vessels predictive of therapeutic efficacy (human middle meningeal artery) and adverse coronary side effects (human coronary artery and human saphenous vein). The authors obtained coronary artery from organ donors (n = 9), middle meningeal artery from patients (n = 11) undergoing craniotomy, and saphenous vein from patients (n = 9) undergoing coronary bypass surgery. Concentration-response curves to eletriptan and sumatriptan were constructed to obtain measurements of efficacy (maximum contraction, E(max)) and potency (concentration eliciting 50% of E(max), EC(50)). The contraction that is likely to be induced at the maximal free plasma concentration (C(max)) was determined by calculating C(max)/EC(50) ratios and by interpolation of the concentration-response curves. Eletriptan and sumatriptan induced concentration-dependent contractions of meningeal artery, coronary artery, and saphenous vein. Eletriptan was less potent than sumatriptan in coronary artery, whereas both compounds had similar potency in meningeal artery and saphenous vein. However, the potency of eletriptan and sumatriptan was higher in meningeal artery than in coronary artery (86-fold for eletriptan and 30-fold for sumatriptan) or saphenous vein (66- and 25-fold). The efficacy of eletriptan and sumatriptan was similar within tissues. The predicted contraction by eletriptan (40 mg and 80 mg) and sumatriptan (100 mg) at free C(max) observed in clinical trials was similar in meningeal artery, whereas in coronary artery and saphenous vein it was lower for 40 mg eletriptan than for sumatriptan. At therapeutic concentrations both eletriptan and sumatriptan contract middle meningeal artery more than coronary artery. This suggests that in patients with healthy coronary arteries, they have a limited propensity to cause adverse coronary side effects. However, both drugs remain contraindicated in patients with coronary artery disease.

Vasoconstriction in human isolated middle meningeal arteries: determining the contribution of 5-HT1B- and 5-HT1F-receptor activation.

Sumatriptan is a 5-HT1B/1D-receptor agonist which also has affinity for 5-HT1F-receptors. The vasoconstrictor effects of sumatriptan are thought to be 5-HT1B-receptor mediated and these receptors have been shown to be expressed in human cranial blood vessels. However, in the same tissue mRNA coding for 5-HT1F-receptors has also been identified and this study addresses the possibility of whether 5-HT1F-receptor activation contributes to vasoconstriction. The ability of two selective 5-HT1B/1D-receptor antagonists (GR125,743 and GR127,935) with no affinity for 5-HT1F-receptors, to inhibit sumatriptan evoked contractions in human isolated middle meningeal artery was investigated. Using a series of 5-HT1B/1D-receptor agonists (sumatriptan, zolmitriptan, CP122,288, L-741,519 and L-741,604), some with high affinity for 5-HTIF-receptors and the non-selective 5-HT-receptor agonists 5-HT and 5-CT, we compared the vasoconstrictor potency of these drugs in human isolated middle meningeal artery with their affinities at cloned human 5-HT1B-, 5-HT1D-and 5-HT1F-receptors expressed in CHO cell lines. GR125,743 antagonized sumatriptan evoked contractions in a competitive manner (apparent pA2 9.1) and GR127,935 antagonized sumatriptan-induced responses in a non-competitive manner (reducing the maximum contraction to 27%). There was a significant correlation between vasoconstrictor potency and 5-HT1B-receptor affinity (r=0.93, P=0.002) but not with 5-HT1D- or 5-HT1F-receptor affinity (r=0.74, P=0.06; r= 0.31, P= 0.49, respectively). These experiments show that in human middle meningeal artery vasoconstriction to sumatriptan-like agents is 5-HT1B-receptor mediated with little if any contribution from 5-HT1F-receptor activation.

Innervation of the human middle meningeal artery: immunohistochemistry, ultrastructure, and role of endothelium for vasomotility

The majority of nerve fibers in the middle meningeal artery and branching arterioles are sympathetic, storing norepinephrine and neuropeptide Y (NPY). A sparse supply of fibers contain acetylcholinesterase activity and immunoreactivity toward vasoactive intestinal peptide (VIP), peptidine histidine methionine (PHM), and calcitonin gene-related peptide (CGRP). Only few substance P and neuropeptide K immunoreactive fibers are noted. Electronmicroscopy shows axons and terminals at the adventitial medial border of the human middle meningeal artery, with a fairly large distance to the smooth muscle cells (>500 nM). Several axon profiles contain vesicles of different types, including putative sensory profiles. The perivascularly stored signal substances, norepinephrine and NPY induced vasoconstrictor. Relaxations were induced by acetylcholine and substance P, and these were significantly reduced in arteries without endothelium, while the responses to norepinephrine, NPY, VIP, PHM, and CGRP were not changed by endothelium removal. Blockade experiments showed that the vasomotor responses to norepinephrine were blocked by prazosin, to NPY by BIBP 3226, acetylcholine by atropin, substance P by RP 67580, and the human α-CGRP response by human α-CGRP 8–37.

Distribution and effects of neuropeptide Y, vasoactive intestinal peptide, substance P, and calcitonin gene-related peptide in human middle meningeal arteries: Comparison with cerebral and temporal arteries

A sparse to moderate supply of nerve fibers containing neuropeptide Y-like immunoreactivity (NPY-LI), vasoactive intestinal polypeptide (VIP-LI), substance P (SP-LI), and calcitonin gene-related peptide (CGRP-LI) was demonstrated in the walls of human middle meningeal arteries. Comparison with similar studies on human cerebral and temporal arteries indicated a similar distribution and density. The immunoreactive material in all three arterial regions was characterized by reversed-phase high pressure liquid chromatography (HPLC) and radioimmunoassay (RIA). The major peak of NPY-LI, VIP-LI, SP-LI, and CGRP-LI in each extract eluted approximately with the same elution volume as that of the corresponding synthetic analogues. The concentration of NPY in the middle meningeal arteries was lower as compared to the temporal arteries. Low concentrations of SP-LI and CGRP-LI were found in the middle meningeal arteries as compared to the cerebral arteries. In isolated ring segments of human middle meningeal and cerebral arteries, NPY caused vasoconstriction but did not potentiate the contractile response of noradrenaline. In the temporal artery, NPY did not induce contraction but potentiated the vasoconstrictor response to noradrenaline. Vasoactive intestinal polypeptide, peptide histidine methionine-27, SP, neurokinin A, and CGRP relaxed all three types of cephalic arteries. The peptide effects were not antagonized by propranolol. atropine, or cimetidine. Comparison of the responses to VIP and SP of vessels from the different regions showed a similar pattern of reactivity. The response to SP was slightly ( p < 0.05) more potent, whereas the responses to CGRP were less potent in the middle meningeal as compared to that in cerebral ( p < 0.005) vessels.

Histamine Receptors in the Isolated Human Middle Meningeal Artery. A Comparison with Cerebral and Temporal Arteries

The subtypes of histamine receptors mediating dilatation of human meningeal arteries have been tested in vitro, using "selective" antagonists, and compared with cerebral and temporal arteries previously examined. Dilatory responses were tested after preconstriction with prostaglandin F2 alpha. Both mepyramine and cimetidine caused a parallel shift to the right of the histamine concentration-response curve, suggesting the presence of both H1- and H2-receptors. Combined treatment with mepyramine and cimetidine caused further displacement of the concentration-response curve to the right. Schild analysis indicated pA2 values of 6.3 for cimetidine and 9.8 for mepyramine in situations of near complete blockade of either of the receptors. Both H1- and H2-receptors seem of importance for the histamine-induced dilatation in meningeal arteries and neither appear to dominate. The data considered in conjunction with our previous findings support the finding that experimental histamine-induced headache due to vasodilatation is intracranial of origin.