Increased alphaCGRP potency and CGRP-receptor antagonist affinity in isolated hypoxic porcine intramyocardial arteries

The effect of intermittent hypoxia training on migraine: a randomized controlled trial

OBJECTIVE

To study the effect of intermittent hypoxia training (IHT) for migraine.

DESIGN

A single-blind, randomized controlled trial. All participants were recruited from a rehabilitation department in an acute university-affiliated hospital.

METHODS

Participants with migraines were randomly assigned to two groups (IHT group and control group). The Migraine Disability Assessment (MIDAS), Visual Analog Scale (VAS), Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), Vascular endothelial growth factor (VEGF), calcitonin gene related peptide (CGRP) and cerebrovascular hemodynamic parameters were collected at baseline and end of the 8^th week. The attack frequencies of migraines were evaluated at 3 months.

RESULTS

Among the 48 subjects, five males and forty-three females, the ages ranged from 19 to 53 years old (mean ± SD = 31.3±7.78). MIDAS, SF-36, VAS, BAI, BDI, VEGF, CGRP and cerebrovascular hemodynamic parameters were improved after IHT intervention. There were significant differences between IHT group and the control group in MIDAS, SF-36, VAS, BAI, BDI, VEGF, CGRP and cerebrovascular hemodynamic parameters at the end of the 8^th weeks (P<0.05). Attack frequencies were improved within 3 months after IH training intervention (P<0.01), but not in the control group (P>0.05). No adverse events occurred during the study.

CONCLUSION

IHT could improve migraines after intervention up to three months. IHT could be an effective method for relieving a migraine.

Hypoxic mechanisms in primary headaches

Background Hypoxia causes secondary headaches such as high-altitude headache (HAH) and headache due to acute mountain sickness. These secondary headaches mimic primary headaches such as migraine, which suggests a common link. We review and discuss the possible role of hypoxia in migraine and cluster headache. Methods This narrative review investigates the current level of knowledge on the relation of hypoxia in migraine and cluster headache based on epidemiological and experimental studies. Findings Epidemiological studies suggest that living in high-altitude areas increases the risk of migraine and especially migraine with aura. Human provocation models show that hypoxia provokes migraine with and without aura, whereas cluster headache has not been reliably induced by hypoxia. Possible pathophysiological mechanisms include hypoxia-induced release of nitric oxide and calcitonin gene-related peptide, cortical spreading depression and leakage of the blood-brain barrier. Conclusion There is a possible link between hypoxia and migraine and maybe cluster headache, but the exact mechanism is currently unknown. Provocation models of hypoxia have yielded interesting results suggesting a novel approach to study in depth the mechanism underlying hypoxia and primary headaches.

Potentiated adrenomedullin-induced vasorelaxation during hypoxia in organ cultured porcine coronary arteries

This study describes the effect of variable oxygen supply on relaxing responses induced by α-calcitonin gene-related peptide (CGRP) and adrenomedullin (AM) on isolated pig coronary arteries in vitro. Organ culture during normoxia (21% of O₂) and hypoxia (5% of O₂) induced a significant leftward shift of the AM concentration-response curves compared with fresh vessels altering the pEC₅₀ values from 6.9 ± 0.04 to 8.0 ± 0.04, whereas the potency (pEC₅₀) of αCGRP was attenuated from 8.8 ± 0.04 to 7.6 ± 0.04. AM₂₂₋₅₂ exerted significant antagonistic effect on AM-induced vasorelaxation in hypoxic and normoxic conditions (apparent pK(B) = 6.8-7.2), whereas no antagonistic effect was observed in fresh and hyperoxic (95%) organ cultured vessels. The antagonistic effect exerted by αCGRP₈₋₃₇ (10⁻⁶·⁵-10⁻⁵·⁵ M) on αCGRP-induced vasodilatation in fresh vessels (derived from Schild plot pA₂ = 7.4 ± 0.1) was unaltered during organ culture. The antagonistic effect exerted by αCGRP₈₋₃₇ (10⁻⁶ M) on AM-induced vasorelaxation in fresh vessels (apparent pK(B) = 7.4 ± 0.1) was absent during hypoxic organ culture. The receptor activity-modifying proteins 1 (RAMP1)/calcitonin-like receptor (CLR) messenger RNA ratio was reduced and RAMP2/CLR messenger RNA ratio was increased during hypoxic and normoxic organ culture compared with fresh vessels. Hypoxic organ culture for 24-72 hours potentiated the AM-induced vasorelaxation through an AM₂₂₋₅₂-sensitive receptor but attenuated the vasorelaxant effect of CGRP through the CGRP receptors. This could possibly be explained by relatively decreased levels of RAMP1, thus favoring RAMP2 + CLR complex (=AM receptor) formation during hypoxic organ culture.

Vascular reactivity to calcitonin gene-related peptide is enhanced in subtotal nephrectomy-salt induced hypertension

In subtotal nephrectomy (SN)- and salt-induced hypertension, calcitonin gene-related peptide (CGRP) plays a compensatory role to attenuate the blood pressure increase in the absence of an increase in the neuronal synthesis and release of this peptide. Therefore, the purpose of this study was to determine whether the mechanism of this antihypertensive activity is through enhanced sensitivity of the vasculature to the dilator actions of this neuropeptide. Hypertension was induced in Sprague-Dawley rats by SN and 1% saline drinking water. Control rats were sham-operated and given tap water to drink. After 11 days, rats had intravenous (drug administration) and arterial (continuous mean arterial pressure recording) catheters surgically placed and were studied in a conscious unrestrained state. Baseline mean arterial pressure was higher in the SN-salt rats (157 ± 5 mmHg) compared with controls (128 ± 3 mmHg). Administration of CGRP (and adrenomedullin) produced a significantly greater dose-dependent decrease in mean arterial pressure in SN-salt rats compared with controls (∼2.0-fold for both the low and high doses). Interestingly, isolated superior mesenteric arterioles from SN-salt rats were significantly more responsive to the dilator effects of CGRP (but not adenomedullin) than the controls (pEC(50), SN-salt, 14.0 ± 0.1 vs. control, 12.0 ± 0.1). Analysis of the CGRP receptor proteins showed that only the receptor component protein was increased significantly in arterioles from SN-salt rats. These data indicate that the compensatory antihypertensive effects of CGRP result from an increased sensitivity of the vasculature to dilator activity of this peptide. The mechanism may be via the upregulation of receptor component protein, thereby providing a more efficient coupling of the receptor to the signal transduction pathways.