Treatment of migraine: update on new therapies

Alkaloids from the rhizomes of Ligusticum striatum exert antimigraine effects through regulating 5-HT1B receptor and c-Jun

ETHNOPHARMACOLOGICAL RELEVANCE

Migraine is a prevalent, complex, painful, and disabling neurovascular disorder that places an enormous social and economic burden on patients. Rhizome Chuanxiong (RCX), the dried rhizomes of Ligusticum striatum DC., has been widely used in the clinic for the treatment of migraine for centuries in China. Total alkaloids (TAs) are considered to be important effective ingredients of L. striatum, especially for cardiovascular and cerebrovascular diseases. However, there has been no study published, to date, reporting the antimigraine effects of TAs from RCX (RCXTAs).

AIM OF THE STUDY

The present study was designed to evaluate the antimigraine effects of RCXTAs and explore the underlying mechanisms in an experimental migraine rat model.

MATERIALS AND METHODS

RCXTAs were prepared in accordance with our previous optimized preparation process. A nitroglycerin-induced migraine model in rats and a reserpine-induced migraine model in mice were established to investigate the effects of RCXTAs on monoamine neurotransmitters in brain tissue, including 5-hydroxytryptamine (5-HT) and its metabolite (5-HIAA). Migraine rats or mice were divided into six groups as follows: control; model; zolmitriptan (1.67 mg/kg); and low-, medium-, and high-dose RCXTAs (12.5, 25, and 50 mg/kg, respectively). The levels of 5-HT and 5-HIAA in the brains of rats and mice were determined by using the enzyme-linked immunosorbent assay method. Pathological changes in the brains of migraine rats were examined by immunohistochemistry. The protein expression of 5-HT_1B receptor, c-Fos, and c-Jun in the periaqueductal gray (PAG) of migraine rats was measured by Western blot.

RESULTS

After preventive administration of RCXTAs to the nitroglycerin-induced migraine rats, the levels of 5-HT and 5-HIAA in the brain tissue were generally upregulated in all three RCXTA dose groups, a finding that was similar to that observed in the control group. Additionally, the 5-HT and 5-HIAA levels were significantly increased in the medium- and high-dose RCXTA groups when compared with the model group (p < 0.01). Therapeutical administration of RCXTAs to reserpine-induced migraine mice also inhibited the reduction of 5-HT and 5-HIAA in the brain (p < 0.01). Both immunohistochemistry and Western blot tests showed that RCXTAs pretreatment has significantly upregulated 5-HT_1B receptor expression and downregulated c-Jun expression in the nitroglycerin-induced migraine rats.

CONCLUSIONS

RCXTAs exerted significant preventive and therapeutic effects on migraine via increasing the levels of 5-HT and 5-HIAA. Upregulation of the expression of monoamine neurotransmitter 5-HT_1B receptor and downregulation of the expression of c-Jun were the possible mechanisms.

Topiramate protects apoE-deficient mice from kidney damage without affecting plasma lipids

Topiramate is an anticonvulsant drug also prescribed for migraine prophylaxis that acts through several mechanisms of action. Several studies indicate that topiramate induces weight loss and a moderate reduction of plasma lipids and glucose. Based on these favourable metabolic effects, aim of this study was to evaluate if topiramate could modulate atherosclerosis development and protect target organs of dysmetabolic conditions. Thirty apoE-deficient mice were divided into three groups and fed for 12 weeks a high fat diet (Control) or the same diet containing topiramate at 0.125% and 0.250%. Body weight, water and food intake were monitored throughout the study. Plasma lipids and glucose levels were measured and a glucose tolerance test was performed. Atherosclerosis development was evaluated in the whole aorta and at the aortic sinus. Histological analysis of liver, kidney and adipose tissue was performed. Topiramate did not affect weight gain and food intake. Glucose tolerance and plasma lipids were not changed and, in turn, atherosclerosis development was not different among groups. Topiramate did not modify liver and adipose tissue histology. Conversely, in the kidneys, the treatment reduced the occurrence of glomerular lipidosis by decreasing foam cells accumulation and reducing the expression of inflammatory markers. Blood urea nitrogen levels were also reduced by treatment. Our results indicate that topiramate does not affect atherosclerosis development, but preserves kidney structure and function. The study suggests that topiramate could be investigated in drug repurposing studies for the treatment of glomerular lipidosis.

The safety and efficacy of the 5-HT 1F receptor agonist lasmiditan in the acute treatment of migraine

INTRODUCTION

Migraine is among the most disabling disorders worldwide, with a significant therapeutic need. Triptans are drugs of choice in the acute attack treatment, but they are contraindicated in patients with vascular conditions due to their potential vasoconstrictive properties. Further limitations include side effects, inconsistency in therapeutic action and possible non-response. Lasmiditan, a highly selective 5-HT1F receptor agonist, is a novel acute anti-migraine substance devoid of vasoconstriction. Areas covered: This article reviews the clinical efficacy and safety of oral and intravenous lasmiditan as a possible acute migraine treatment. We analyze all currently available results in Phase I to III studies. Expert opinion: Lasmiditan is a promising acute migraine therapy, in particular for patients at cardiovascular risk. Phase II and the first Phase III clinical trials show a significant better headache response in comparison to placebo. The efficacy of lasmiditan proves that vasoconstriction is not essential for acute migraine therapy and thereby points, in addition to a well-established trigeminal contribution, to central neuronal mechanisms in migraine pathophysiology. Lasmiditan penetrates the blood-brain barrier and CNS associated adverse events are common, but mostly in mild to moderate severity. The results of long-term Phase III studies will determine if these adverse events represent a limitation in clinical practice.

Association between functional gastrointestinal disorders and migraine in children and adolescents: a case-control study

BACKGROUND

Functional gastrointestinal disorders and migraine are both common causes of medical attention. We have previously shown an association between migraine and infant colic. In this case-control study, we aimed to establish whether there is an association between migraine and other functional gastrointestinal disorders in children and adolescents.

METHODS

We included children and adolescents aged 6-17 years presenting to the emergency department of four tertiary hospitals in France and Italy. Patients diagnosed with either migraine or tension-type headache by the hospital's paediatric neurologist were enrolled as cases. Patients presenting to the emergency department with minor trauma and no history of recurrent headache were enrolled as controls. Investigators masked to a patient's group allocation diagnosed functional gastrointestinal disorders using the Rome III diagnostic criteria. Univariable and multivariable analyses were done to identify specific disorders and baseline factors associated with migraines and tension-type headache.

FINDINGS

Between Nov 1, 2014, and Jan 31, 2015, we enrolled 648 controls and 424 cases (257 patients with migraine and 167 with tension-type headache). 83 (32%) children and adolescents in the migraine group were diagnosed with functional gastrointestinal disorders compared with 118 (18%) in the control group (p<0·0001). Multivariable logistic regression showed a significant association between migraine and three gastrointestinal disorders: functional dyspepsia (odds ratio 10·76, 95% CI 3·52-32·85; p<0·0001), irritable bowel syndrome (3·47, 1·81-6·62; p=0·0002), and abdominal migraine (5·87, 1·95-17·69; p=0·002). By contrast, there was an inverse association between migraine and functional constipation (0·34, 0·14-0·84, p=0·02). 41 (25%) participants with tension-type headache had functional gastrointestinal disorders, which did not significantly differ from the prevalence of these disorders in the control group (p=0·07); no significant association was noted between any functional gastrointestinal disease and tension-type headaches.

INTERPRETATION

Three abdominal-pain-related functional gastrointestinal disorders were associated with migraine in children and adolescents. These findings are of value to the diagnosis and management of these common diseases. Future studies should investigate whether antimigraine drugs are of benefit in functional gastrointestinal disorders.

FUNDING

None.

Fathoming the kynurenine pathway in migraine: why understanding the enzymatic cascades is still critically important

Kynurenine pathway, the quantitatively main branch of tryptophan metabolism, has been long been considered a source of nicotinamide adenine dinucleotide, although several of its products, the so-called kynurenines, are endowed with the capacity to activate glutamate receptors, thus potentially influencing a large group of functions in the central nervous system (CNS). Migraine, a largely unknown pathology, is strictly related to the glutamate system in the CNS pathologic terms. Despite the large number of studies conducted on migraine etio-pathology, the kynurenine pathway has been only recently linked to this disease. Nonetheless, some evidence suggests an intriguing role for some kynurenines, and an exploratory study on the serum kynurenine level might be helpful to better understand possible alterations of the kynurenine pathway in patients suffering from migraine.

Understanding migraine using dynamic network biomarkers

Background

Mathematical modeling approaches are becoming ever more established in clinical neuroscience. They provide insight that is key to understanding complex interactions of network phenomena, in general, and interactions within the migraine-generator network, in particular.

Purpose

In this study, two recent modeling studies on migraine are set in the context of premonitory symptoms that are easy to confuse for trigger factors. This causality confusion is explained, if migraine attacks are initiated by a transition caused by a tipping point.

Conclusion

We need to characterize the involved neuronal and autonomic subnetworks and their connections during all parts of the migraine cycle if we are ever to understand migraine. We predict that mathematical models have the potential to dismantle large and correlated fluctuations in such subnetworks as a dynamic network biomarker of migraine.

Topiramate and cognitive impairment: evidence and clinical implications

Topiramate is an antiepileptic drug (AED) with multiple mechanisms of action that has been shown to be effective in a number of neuropsychiatric disorders. However, cognitive dysfunction is frequently observed in such patients, often representing a relevant challenge in their management. Moreover, there is a long-held recognition that AEDs may profoundly affect cognitive functions. This paper reviews available data on cognitive adverse events in patients with neurological disorders treated with topiramate, discussing the role of different contributing factors such as the pharmacological properties of the drug, the specific features of the brain disorder, and other variables pertinent to the discussion. All studies agree that up to 10% of patients may complain of treatment-emergent adverse events on cognition. Such problems occur early during treatment (i.e. within 6 weeks) and emerge in a dose-dependent fashion, suggesting that such prevalence may be significantly reduced using the drug in monotherapy and adopting individualized doses and titration schedules. The magnitude of the problem is generally mild to moderate and the subjective perception of the patient needs to be taken into account. In fact, apart from language problems, data are not conclusive. Comparisons with new AEDs are limited to levetiracetam and lamotrigine, in both cases generally disfavoring topiramate, while data regarding first-generation AEDs show clear differences only for verbal fluency.

Emerging therapeutic options for acute migraine: focus on the potential of lasmiditan

The serotonin receptor agonist triptan drugs (5-HT1B/1D receptor agonists) have been in use for over 20 years in the abortive management of migraine. Although clearly effective, their ability to produce vasoconstriction in cerebral and coronary arteries, thought to be mediated by their high affinity for the 5-HT1B receptor, has been a limitation to their use in certain patient populations. Variable potency triptan binding at the 5-HT1F receptor occurs in addition to binding at the 5-HT1B and 5-HT1D receptors. A more selective serotonin agonist without 5-HT1B-mediated vasoconstriction might prove efficacious yet safer. The 5-HT1F receptor has been targeted as a site of action for such a drug. In experimental models, 5-HT1F receptor agonists have been shown to block neurogenic inflammation and c-Fos expression in neural tissue and, as well, show no evidence of vasoconstriction in vascular tissue models in vitro. In clinical trials, efficacy in the abortive management of migraine has been established. Lasmiditan (LY573144), a selective 5-HT1F receptor agonist (K1=2.21 μM), showed efficacy in its primary endpoint, with a 2-hour placebo-subtracted headache response of 28.8%, though with frequent reports of dizziness, paresthesias, and vertigo. Study results support an emerging central neuronal mechanism of migraine pathophysiology. This review traces the history and use of 5-HT1F receptor agonists, now referred to as neurally acting anti-migraine agents in migraine management.

Neuromagnetic abnormality of motor cortical activation and phases of headache attacks in childhood migraine

The cerebral cortex serves a primary role in the pathogenesis of migraine. This aberrant brain activation in migraine can be noninvasively detected with magnetoencephalography (MEG). The objective of this study was to investigate the differences in motor cortical activation between attacks (ictal) and pain free intervals (interictal) in children and adolescents with migraine using both low- and high-frequency neuromagnetic signals. Thirty subjects with an acute migraine and 30 subjects with a history of migraine, while pain free, were compared to age- and gender-matched controls using MEG. Motor cortical activation was elicited by a standardized, validated finger-tapping task. Low-frequency brain activation (1∼50 Hz) was analyzed with waveform measurements and high-frequency oscillations (65–150 Hz) were analyzed with wavelet-based beamforming. MEG waveforms showed that the ictal latency of low-frequency brain activation was significantly delayed as compared with controls, while the interictal latency of brain activation was similar to that of controls. The ictal amplitude of low-frequency brain activation was significantly increased as compared with controls, while the interictal amplitude of brain activation was similar to that of controls. The ictal source power of high-frequency oscillations was significantly stronger than that of the controls, while the interictal source power of high-frequency oscillations was significantly weaker than that of controls. The results suggest that aberrant low-frequency brain activation in migraine during a headache attack returned to normal interictally. However, high-frequency oscillations changed from ictal hyper-activation to interictal hypo-activation. Noninvasive assessment of cortical abnormality in migraine with MEG opens a new window for developing novel therapeutic strategies for childhood migraine by maintaining a balanced cortical excitability.

St. John's wort reversal of meningeal nociception: a natural therapeutic perspective for migraine pain

Despite a number of antimigraine drugs belonging to different pharmacological classes are available, there is a huge unmet need for better migraine pharmacotherapy. We here demonstrated the capability of Hypericum perforatum, popularly called St. John's wort (SJW), to relieve meningeal nociception in an animal model induced by administration of the nitric oxide (NO) donors glyceryl trinitrate (GTN) and sodium nitroprusside (SNP). GTN and SNP produced a delayed meningeal inflammation, as showed by the upregulation of interleukin (IL)-1β and inducible NO synthase (iNOS), and a prolonged cold allodynia and heat hyperalgesia with a time-course consistent with NO-induced migraine attacks. A single oral administration of a SJW dried extract (5mg/kg p.o.) counteracted the nociceptive behaviour and the overexpression of IL-1β and iNOS. To clarify the cellular pathways involved, the expression of protein kinase C (PKC) and downstream effectors was detected. NO donors increased expression and phosphorylation of PKCγ, PKCɛ and transcription factors, such as nuclear factor (NF)-κB, cyclic AMP response element binding protein (CREB), Signal Transducer and Activator of Transcription (STAT)-1. All these molecular events were prevented by SJW and hypericin, a SJW main component. In conclusion, SJW counteracted the NO donor-induced pain hypersensitivity and meningeal activation by blocking PKC-mediated pathways involving NF-κB, CREB, STAT1. These results might suggest SJW as an innovative and safe perspective for migraine pain.

A case of migraine without aura that was successfully treated with an herbal medicine

OBJECTIVE

Migraine is a common neurologic condition characterized by the disabling effects it has on the patient. Despite recent progress in drug development, better pharmacotherapies against migraine are still needed. This report describes an herbal medicine that has a strong pain-relieving effect against migraine.

PATIENT

This case involved a 49-year-old woman with a 16-year history of headaches. Migraine without aura had been diagnosed at age 47 years. Despite taking antiepileptic drugs as prophylaxis, she had migraines almost three times a week, especially in the morning. As a result, 3 months before her visit to the study clinic she was prescribed sumatriptan, which she had to take for each attack. However, sumatriptan sometimes failed to work as a painkiller, and the patient did not want to continue taking it because she was worried about overuse.

INTERVENTION AND OUTCOME

According to traditional Japanese (Kampo) and Chinese herbal medicine, the patient was prescribed an oral sanno-shashin-to (Xie Xin Tang) extract formula to take at night to prevent her migraines. Soon after she started taking the formula, the intensity of her morning headaches markedly decreased, to the extent that triptans were no longer needed. Furthermore, her residual headaches quickly disappeared after the additional administration of the formula in the morning.

CONCLUSIONS

Sanno-shashin-to might have both prophylactic and therapeutic effects against migraine without aura. Although the underlying mechanism behind the effectiveness of this herbal medicine against migraine has not been fully elucidated, it is a possible option for the treatment of this type of headache.

Acute and preventive treatment of migraine

PURPOSE OF REVIEW

Migraine remains underdiagnosed and undertreated despite advances in the understanding of its pathophysiology and management. This article focuses on acute and preventive treatment of migraine, including the mechanisms of action, dosing and side effects of medications, and strategies for the most effective care.

RECENT FINDINGS

Best practice suggests that acute migraine treatment should be stratified based on the severity of the individual event, with a goal of returning the patient to full function within 2 hours of treatment. Migraine prevention strategies continue to be underused in the United States. More than 1 in 4 patients with migraines may be candidates for preventive therapy. To obtain the best results from preventive therapy, slow titration to an adequate dose for an adequate timeframe with good documentation of the results is recommended.

SUMMARY

This article reviews several options for managing acute attacks, including information on expected efficacy, dosing, and adverse effects. Strategies for effective application of acute therapies are discussed. Prevention can be added to acute therapy depending on headache characteristics such as frequency, severity, disability, and the presence of comorbid conditions. The mechanisms of action of preventive medications and strategies for their most effective use are discussed.

Management of acute and chronic migraine

PURPOSE OF REVIEW

We highlight the recent clinical trials for the management of acute and chronic migraine.

RECENT FINDINGS

In women with menstrual migraine, triptans seem to be well tolerated irrespective of whether or not patients are taking oestrogen-containing contraceptives or have comorbidities that indicate increased cardiovascular risk. The new acute drug, telcagepant, a calcitonin gene-related peptide (CGRP) antagonist, is safe for long-term use (up to 18 months) in migraine patients with stable coronary artery disease in whom the use of triptans is not advisable. From the pooled analysis of the two Phase III Research Evaluating Migraine Prophylaxis Therapy studies of onabotulinumtoxinA (BOTOX) in chronic migraineurs, it clearly emerged that efficacy increases overtime (up to 56 weeks) and paralleled self-perceived improvement in quality of life. Effectiveness was also observed in patients with severely disabling headaches, who met criteria for triptan abuse and were refractory to several prophylactic treatments. Finally, combination of preventive pharmacological agents with different action mechanisms may be the next frontier in therapeutic advancements for treating migraine.

SUMMARY

Although triptans are safe and well tolerated, CGRP antagonists may be an option for nonresponsive patients or those in whom the use of triptans is not advisable. New drugs and combinations of old therapeutic options may help patients with severe forms of headache.

Frovatriptan: a review of its use in the acute treatment of migraine

Frovatriptan (Migard®; Frova®) is an orally administered triptan approved for the acute treatment of adults with migraine, with or without aura. This article reviews the pharmacology of frovatriptan, focusing on its efficacy and tolerability. The precise mechanism of action of frovatriptan is unknown, but is thought to stem from agonism at serotonin 5-HT(1B) and 5-HT(1D) receptors, resulting in inhibition of intracranial and extracerebral artery vasodilation, along with possible anti-inflammatory and pain inhibiting effects. Frovatriptan appears to be functionally selective for 5-HT receptors in human basilar arteries over coronary arteries, which could translate into a low cardiovascular risk. In contrast to other triptans, frovatriptan has a long terminal elimination half-life in blood of ≈26 hours, which can be expected to be associated with a sustained treatment effect. Oral frovatriptan 2.5 mg was efficacious in patients with moderate to severe migraine attacks; in randomized, double-blind trials the proportion of patients with headache response at 2 hours (primary endpoint) was consistently significantly higher in frovatriptan than placebo groups. Frovatriptan was generally well tolerated in short-term clinical trials and when used over the longer term. The most frequent treatment-emergent adverse events occurring at a frequency ≥1% higher in frovatriptan than placebo recipients were dizziness, fatigue, headache, paraesthesia, flushing, skeletal pain, hot or cold sensation, dry mouth, chest pain and dyspepsia. In a study in patients with coronary artery disease, or who were at high risk of coronary artery disease, there was no increase over placebo in the occurrence of clinically significant ECG changes or in cardiac rhythm disturbances. In a further trial, frovatriptan administered early in a migraine attack was more efficacious than placebo followed by later administration of frovatriptan as pain progressed. Three crossover trials compared early administration of frovatriptan 2.5 mg with almotriptan 12.5 mg, rizatriptan 10 mg and zolmitriptan 2.5 mg in patients with migraine. There were no significant between-group differences in patient drug preference scores (primary endpoint) or in other endpoints, except for headache recurrence, which favoured frovatriptan in two of the trials. The trials did not test noninferiority of frovatriptan to the comparator. In a placebo-controlled trial that included a sumatriptan active treatment arm, sumatriptan 100 mg was significantly more efficacious than frovatriptan 2.5 mg for this primary endpoint. Frovatriptan was generally better tolerated than all four triptan comparators. In summary, frovatriptan was an efficacious acute treatment for moderate to severe migraine attacks and had a favourable tolerability profile, although in a single trial, it was not as efficacious as sumatriptan. Administration of frovatriptan early in an attack while the attack was at a mild level of intensity was more efficacious than late administration. Furthermore, in clinical trials adopting this early administration strategy, frovatriptan was not significantly less efficacious than almotriptan, rizatriptan and zolmitriptan, appeared to have a more sustained treatment effect, and was better tolerated than the comparators. Frovatriptan provides an alternative treatment for migraine, especially in patients who have had adverse events or frequent headache recurrences with triptans or other antimigraine drugs, and who are amenable to adopting an early administration strategy.

Overview of migraine treatment

SUMMARY Migraine is ranked as the 19th top cause of disability worldwide by WHO. Despite advancements in migraine-specific acute treatment, only a minority of patients utilize these medications. Specific pharmacologic treatments consist of the ergot alkaloids and triptans (serotonin 5-HT1B/1D receptor agonists). Both classes are regarded as relatively safe and effective; however, there is a greater concern for vasoconstrictive effects with the ergots, which limits their use. Triptans transformed migraine therapy, setting in motion revolutionary research that heightened our understanding of migraine mechanisms. However, one in three migraineurs may be triptan nonresponders and there is a group of migraine patients that remains ‘refractory’ to conventional pharmacologic migraine therapy. This article discusses the approach to migraine management, reviews currently available acute and preventive pharmacologic and nonpharmacologic treatment options for migraine headache, as well as briefly focuses on novel and upcoming medicines presently under investigation.

Prevalence, clinical features and potential therapies for fibromyalgia in primary headaches

Fibromyalgia (FM) syndrome is predominantly related to generation and persistence of central sensitization, which is an aggravating factor for chronic headaches. This review aims to examine the last 11 years of studies on FM and primary headache comorbidity, focusing on prevalence, clinical features and treatments. Chronic forms of migraine and tension-type headache show a high frequency of FM comorbidity. The symptoms characterizing headache patients presenting with FM comorbidity are high headache frequency, poor sleep quality, pericranial tenderness, anxiety and reduction of physical performances. The effects of headache-preventive drugs on factors favoring FM comorbidity were poorly evaluated. Nonpharmacological approaches such as transcranial magnetic stimulation may be an option for treatment of chronic migraine associated with FM.

Effect of systemic kynurenine on cortical spreading depression and its modulation by sex hormones in rat

BACKGROUND

The aura symptoms in migraine are most likely due to cortical spreading depression (CSD). CSD is favored by NMDA receptor activation and increased cortical excitability. The latter probably explains why migraine with aura may appear when estrogen levels are high, like during pregnancy. Kynurenic acid, a derivative of tryptophan metabolism, is an endogenous NMDA receptor antagonist whose cerebral concentrations can be augmented by systemic administration of its precursor L-kynurenine.

OBJECTIVE

To determine if exogenous administration of L-kynurenine is able to influence KCl-induced CSD in rat, if the effect is sex-dependent and if it differs in females between the phases of the estrous cycle.

METHODS

Adult Sprague-Dawley rats (n=8/group) received intraperitoneal (i.p.) injections of L-kynurenine (L-KYN, 300 mg/kg), L-KYN combined with probenecid (L-KYN+PROB) that increases cortical concentration of KYNA by blocking its excretion from the central nervous system, probenecid alone (PROB, 200 mg/kg) or NaCl. Cortical kynurenic acid concentrations were determined by HPLC (n=7). Thirty minutes after the injections, CSDs were elicited by application of 1M KCl over the occipital cortex and recorded by DC electrocorticogram. In NaCl and L-KYN groups, supplementary females were added and CSD frequency was analyzed respective to the phases of the estrous cycle determined by vaginal smears.

RESULTS

In both sexes, PROB, L-KYN and L-KYN+PROB increased cortical kynurenic acid level. PROB, L-KYN and L-KYN+PROB with increasing potency decreased CSD frequency in female rats, while in males such an effect was significant only for L-KYN+PROB. The inhibitory effect of L-KYN on CSD frequency in females was most potent in diestrus.

CONCLUSION

L-Kynurenine administration suppresses CSD, most likely by increasing kynurenic acid levels in the cortex. Females are more sensitive to this suppressive effect of L-kynurenine than males. These results emphasize the role of sex hormones in migraine and open interesting novel perspectives for its preventive treatment.

The use of plants for the production of therapeutic human peptides

Peptides have unique properties that make them useful drug candidates for diverse indications, including allergy, infectious disease and cancer. Some peptides are intrinsically bioactive, while others can be used to induce precise immune responses by defining a minimal immunogenic region. The limitations of peptides, such as metabolic instability, short half-life and low immunogenicity, can be addressed by strategies such as multimerization or fusion to carriers, to improve their pharmacological properties. The remaining major drawback is the cost of production using conventional chemical synthesis, which is also difficult to scale-up. Over the last 15 years, plants have been shown to produce bioactive and immunogenic peptides economically and with the potential for large-scale synthesis. The production of peptides in plants is usually achieved by the genetic fusion of the corresponding nucleotide sequence to that of a carrier protein, followed by stable nuclear or plastid transformation or transient expression using bacterial or viral vectors. Chimeric plant viruses or virus-like particles can also be used to display peptide antigens, allowing the production of polyvalent vaccine candidates. Here we review progress in the field of plant-derived peptides over the last 5 years, addressing new challenges for diverse pathologies.

Recurrent headaches with visual disturbance

Headache, particularly migraine, is the commonest neurological problem with which patients present to general practitioners and neurologists. Episodic migraine affects up to 18% of women and 6% of men. Acute migraine attacks can be severely disabling and chronic migraine is even more disabling. Of the mental and neurological disorders, migraine ranks eighth worldwide in terms of disability. Migraine is one of the primary headaches and may occur with or without aura. Differentiation from other severe primary headaches, such as cluster headache, is important for management. The vast majority of patients with migraine can be satisfactorily helped and treated. This involves acute and prophylactic drug therapy and management of triggers. In patients with migraine, medication overuse headache and chronic migraine need to be identified and treated.