The Effect of Cortical Spreading Depression Induced Episodic Headache on Blood-Brain Barrier Structure and Function

Previous research has demonstrated that BBB structure and function are altered as a result of various neurological disorders including ischemic stroke, traumatic brain injury, epilepsy, and infections of the brain. Additionally, the BBB has also been shown to alter its function in response to nociception. Despite the strong evidence for BBB alterations in both neurological disorders and pain, there is still debate on whether BBB permeability is altered in episodic headache disorders such as migraine. Cortical spreading depression (CSD) in the CNS is suggested as a common mechanism contributing to both headache production and BBB changes. In previous studies examining BBB changes in response to CSD, animals were anesthetized during the study, preventing any behavioral assessments. Additionally, in studies examining CSD induced nociceptive behaviors, BBB permeability was not assessed. Therefore, this work represents the first joint assessment of nociceptive responses and BBB integrity in response to CSD. In these studies, we observed a transient increase in BBB paracellular permeability in the cortex, but not brainstem, in response to KCl induced CSD. Additionally, at corresponding time points, we found that KCl induced CSD reduced periorbital withdrawal thresholds and rearing behavior, indicative of a state of facial mechanical allodynia. Despite strong evidence for CNS involvement in headache disorders, drug development for headache disorders remains focused on peripheral targets. Difficulty in delivering drugs across the BBB may partially account for this disparity. In this work, we demonstrated that KCl induced CSD increased the CNS uptake of radiolabeled sumatriptan in both the cortex and the brainstem. We also found that KCl induced CSD increased the expression of the putative sumatriptan transporter Oatp1a4 in the brainstem, which likely underlies the observed increased brainstem permeability to sumatriptan following CSD induction. Repeated CSD events may be harmful long-term. Therefore, we also investigated whether pre-treatment with the migraine prophylactic topiramate could prevent the CSD induced increase in BBB permeability. In these studies a single dose of topiramate was not able to block CSD induced BBB changes; importantly, topiramate and other migraine prophylactic drugs are typically given chronically to reduce the occurrence and severity of attacks. Therefore further studies should be conducted to determine if chronic topiramate treatment has any protective effects on the BBB in this model. Often, changes in BBB permeability are accompanied by decreases in tight junction protein expression, including occludin, claudin-5, and ZO-1. Here, however, we did not observe any changes in expression of either occludin or claudin-5 in response to cortical KCl induced CSD. BBB permeability can also be decreased through changes in TJ protein localization. We observed a change in claudin-5, but not occludin or ZO-1, localization in rats where CSD was induced with cortical KCl injections. This was recapitulated in an in vitro model using bEnd.3 mouse brain endothelial cells. Additionally, treatment of these cells with a CSD cocktail comprised of KCl, ATP, and glutamate with a pH of 6.8 was also able to cause claudin-5 relocalization. Interestingly, potassium influx mechanisms including the Na+/K+ ATPase and Kir6 channels have been implicated in BBB regulation. We found that blockade of these mechanisms with digoxin or AMP-PNP, respectively was able to prevent KCl or CSD cocktail-induced claudin-5 relocalization. Since claudin-5 is the component of the BBB which regulates permeability to ions and small molecules, these changes may represent the BBB’s effort to re-establish membrane ionic equilibrium. Finally, this work addresses sex differences in migraine, particularly as they relate to the BBB. In previous studies, female sex hormones have been shown to facilitate both nociception and CSD production. Here, we found that female rats had a more intense response to cortical KCl induced CSD. Additionally, we demonstrated that the female sex hormone 17-β-estradiol can, on its own, induce nociceptive behaviors in rats. Finally we observed several changes in BBB structure and function related to sex hormones. Consistent with previous studies, we found that ovariectomy increased BBB permeability. When investigating estradiol induced molecular changes at the BBB, we turned our attention to the sodium/hydrogen exchanger NHE1 due to its role in regulating cell excitability, its reported functional regulation by estradiol, and in vitro data implying expression may play a role in triptan uptake. Here, we found that estradiol reduces NHE1 expression in a concentration dependent manner in GPNT rat brain endothelial cells, but not other CNS cell types such as microglia or astrocytes. Additionally, we found that testosterone did not affect its expression. These data suggest that estradiol may control CNS ion balance and excitability due to its regulation of BBB ion exchangers such as NHE1. Together, the results presented herein demonstrate that CSD induces episodic headache-like behaviors that coincide with alterations in BBB structure and function. These changes can be taken advantage of clinically, by dosing drugs at specific times to increase their access to the CNS. On the other hand, episodic headache induced BBB changes may also produce long-term deleterious effects. Therefore, further studies should be conducted to fully elucidate the mechanisms behind headache induced BBB changes so that they may be prevented through appropriate therapeutic interventions.Release after 21-May-201

Noxa in rheumatic diseases: present understanding and future impact

Impaired programmed cell death is an important contributing mechanism in the development of chronic inflammatory and autoimmune diseases. Overexpression of Bcl-2 family proteins in such diseases has led to the concept of targeted suppression of these proteins as a primary therapeutic strategy. However, limited success with this approach has prompted pharmacologists to look at the other side of the coin, with the aim of reactivating jeopardized pro-apoptotic proteins that may neutralize Bcl-2 or other anti-apoptotic molecules. In this effort, BH3-only proteins have gained recent attention as endogenous molecules for the sensitization of resistant cells to undergo apoptosis. Among the BH3-only family, Noxa stands out as exceptional for its specificity to bind Mcl-1 and Bcl-2 and blunt their biological properties. Noxa is now being tested as a promising therapeutic target in cancer biology. Nonetheless, its role and clinical application still lack validation in autoimmune diseases, including rheumatic conditions. This is partly attributed to the significant gap in our understanding of its regulatory role and how either overexpression of Noxa or delivery of BH3 mimetics could be therapeutically exploited. In this review we highlight some recent studies in RA, OA, SLE and SS suggesting that Noxa may be used as a potential therapeutic target to circumvent invasive and tissue destructive processes in these rheumatic diseases

17-β-Estradiol induces spreading depression and pain behavior in alert female rats

Aims: Test the putative contribution of 17-beta-estradiol in the development of spreading depression (SD) events and head pain in awake, non-restrained rats. Main Methods: Female, Sprague-Dawley rats were intact or underwent ovariectomy followed one week later by surgery to place electrodes onto the dura to detect epidural electroencephalographic activity (dEEG). dEEG activity was recorded two days later for 12 hours after systemic administration of 17-beta-estradiol (180 mu g/kg, i.p.). A separate set of rats were observed for changes in exploratory, ambulatory, fine, and rearing behaviors; periorbital allodynia was also assessed. Key Findings: A bolus of 17-beta-estradiol significantly elevated serum estrogen levels, increased SD episodes over a 12-hour recording period and decreased rearing behaviors in ovariectomized rats. Pre-administration of ICI 182,780, an estrogen receptor antagonist, blocked 17-beta-estradiol-evoked SD events and pain behaviors; similar results were observed when the antimigraine therapeutic sumatriptan was used. Significance: These data indicate that an estrogen receptor-mediated mechanism contributes to SD events in ovariectomized rats and pain behaviors in both ovariectomized -and intact-rats. This suggests that estrogen plays a different role in each phenomenon of migraine where intense fluctuations in concentration may influence SD susceptibility. This is the first study to relate estrogen peaks to SD development and pain behaviors in awake, freely moving female rats, establishing a framework for future preclinical migraine studies.University of Arizona Medical Pharmacology Departmental funding; NIH [5 RO1 DA 11271-18, 5 RO1 NS 42652-14]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

A Drug Repurposing Approach Reveals Targetable Epigenetic Pathways in Plasmodium vivax Hypnozoites.

Radical cure of Plasmodium vivax malaria must include elimination of quiescent "hypnozoite" forms in the liver; however, the only FDA-approved treatments are contraindicated in many vulnerable populations. To identify new drugs and drug targets, we screened the Repurposing, Focused Rescue, and Accelerated Medchem library against P. vivax liver stages and identified the DNA methyltransferase inhibitors hydralazine and cadralazine as active against hypnozoites. We then used bisulfite sequencing and immunostaining to identify cytosine modifications in the infectious stage (sporozoites) and liver stages, respectively. A subsequent screen of epigenetic inhibitors revealed hypnozoites are broadly sensitive to histone acetyltransferase and methyltransferase inhibitors, indicating that several epigenetic mechanisms are likely modulating hypnozoite persistence. Our data present an avenue for the discovery and development of improved radical cure antimalarials