Involvement of adenosine signaling pathway in migraine pathophysiology: A systematic review of clinical studies

Spinal manipulations for migraine: an updated systematic review and meta-analysis of randomized clinical trials

OBJECTIVE

This update of a systematic review evaluates the effectiveness of spinal manipulations as a treatment for migraine headaches.

BACKGROUND

Spinal manipulation therapy (SMT) is sometimes used to treat migraine headaches; however, the biological plausibility and safety of SMT have repeatedly been questioned.

METHODS

Amed, Embase, MEDLINE, CINAHL, Mantis, Index to Chiropractic Literature, and Cochrane Central were searched from inception to September 2023. Randomized clinical trials (RCTs) investigating spinal manipulations (performed by various healthcare professionals including physiotherapists, osteopaths, and chiropractors) for treating migraine headaches in human subjects were considered. Other types of manipulative therapy, i.e., cranial, visceral, and soft tissue were excluded. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used to evaluate the certainty of evidence.

RESULTS

Three more RCTs were published since our first review; amounting to a total of 6 studies with 645 migraineurs meeting the inclusion criteria. Meta-analysis of six trials showed that, compared with various controls (placebo, drug therapy, usual care), SMT (with or without usual care) has no effect on migraine intensity/severity measured with a range of instruments (standardized mean difference [SMD] - 0.22, 95% confidence intervals [CI] - 0.65 to 0.21, very low certainty evidence), migraine duration (SMD - 0.10; 95% CI - 0.33 to 0.12, 4 trials, low certainty evidence), or emotional quality of life (SMD - 14.47; 95% CI - 31.59 to 2.66, 2 trials, low certainty evidence) at post-intervention. A meta-analysis of two trials showed that compared with various controls, SMT (with or without usual care) increased the risk of AEs (risk ratio [RR] 2.06; 95% CI 1.24 to 3.41, numbers needed to harm = 6; very low certainty evidence). The main reasons for downgrading the evidence were study limitations (studies judged to be at an unclear or high risk of bias), inconsistency (for pain intensity/severity), imprecision (small sizes and wide confidence intervals around effect estimates) and indirectness (methodological and clinical heterogeneity of populations, interventions, and comparators).

CONCLUSIONS

The effectiveness of SMT for the treatment of migraines remains unproven. Future, larger, more rigorous, and independently conducted studies might reduce the existing uncertainties.

Metabolic Dysfunction in New-Onset Idiopathic Intracranial Hypertension: Identification of Novel Biomarkers

OBJECTIVE

Idiopathic intracranial hypertension (IIH) is a neurometabolic disease with an increasing incidence. The pathophysiology is unknown, but improvement of diagnosis and management requires discovery of novel biomarkers. Our objective was to identify such candidate biomarkers in IIH, and secondarily, test for associations between identified metabolites and disease severity.

METHODS

This is a prospective case-control study with collection of cerebrospinal fluid (CSF), serum, and clinical data from new-onset, treatment-naïve patients with IIH (n = 60). Patients were included consecutively from 2 tertiary headache centers in Denmark, and age, sex, and body mass index (BMI) -matched healthy controls (n = 35) were recruited. Clinical data were retrieved at ocular remission (n = 55). Samples were analyzed using non-targeted mass spectrometry.

RESULTS

Serum sphingosine 1-phosphate (S1P), adenosine, and glutamate were 0.46-fold (q < 0.0001), 0.25-fold (q = 0.0048), and 0.44-fold (q < 0.0001) lower, respectively, in IIH. CSF stearoyl-lysophosphatidylcholine (LysoPC-18) and 2-palmitoyl-lysophosphatidylcholine (LysoPC-16) were 0.42 (q = 0.0025) and 0.37 (q < 0.001) -fold lower. LysoPC-18 was higher in patients with moderate-severe versus mild papilledema (p = 0.022). LysoPC-18 correlated positively with retinal nerve fiber layer thickness (p = 0.0012, r = 0.42) and inversely with mean deviation on automated perimetry (p = 0.01, r = -0.35). Higher baseline serum S1P (p = 0.018) and lower CSF LysoPC-16 (p = 0.003) were associated with optic nerve atrophy at ocular remission. Pathway analysis suggests dysregulated lipid metabolism and redox disturbances in new-onset IIH.

INTERPRETATION

We identify perturbed metabolism in new-onset IIH. S1P and LysoPC-16 demonstrate potential prognostic value due to association with subsequent optic nerve atrophy. This association between specific, differential metabolites and outcome provides substantial evidence for novel biomarkers of clinical significance that should be the focus of further targeted studies. ANN NEUROL 2024;96:595-607.

AMPK activation attenuates central sensitization in a recurrent nitroglycerin-induced chronic migraine mouse model by promoting microglial M2-type polarization

BACKGROUND

Energy metabolism disorders and neurogenic inflammation play important roles in the central sensitization to chronic migraine (CM). AMP-activated protein kinase (AMPK) is an intracellular energy sensor, and its activation regulates inflammation and reduces neuropathic pain. However, studies on the involvement of AMPK in the regulation of CM are currently lacking. Therefore, this study aimed to explore the mechanism underlying the involvement of AMPK in the central sensitization to CM.

METHODS

Mice with recurrent nitroglycerin (NTG)-induced CM were used to detect the expression of AMPK protein in the trigeminal nucleus caudalis (TNC). Following intraperitoneal injection of the AMPK activator 5-aminoimidazole-4-carboxyamide ribonucleoside (AICAR) and inhibitor compound C, the mechanical pain threshold, activity level, and pain-like behaviors in the mice were measured. The expression of calcitonin gene-related peptide (CGRP) and cytokines, M1/M2 microglia, and NF-κB pathway activation were detected after the intervention.

RESULTS

Repeated NTG injections resulted in a gradual decrease in AMPK protein expression, and the negative regulation of AMPK by increased ubiquitin-like plant homeodomain and RING finger domain 1 (UHRF1) expression may counteract AMPK activation by increasing ADP/ATP. AICAR can reduce the hyperalgesia and pain-like behaviors of CM mice, improve the activity of mice, reduce the expression of CGRP, IL-1β, IL-6, and TNF-α in the TNC region, and increase the expression of IL-4 and IL-10. Moreover, AMPK in TNC was mainly located in microglia. AICAR could reduce the expression of inducible NO synthase (iNOS) in M1 microglia and increase the expression of Arginase 1 (Arg1) in M2 microglia by inhibiting the activation of NF-κB pathway.

CONCLUSIONS

AMPK was involved in the central sensitization of CM, and the activation of AMPK reduced neuroinflammation in NTG-induced CM mice. AMPK may provide new insights into interventions for energy metabolism disorders and neurogenic inflammation in migraine.

Novel Therapeutic Targets for Migraine

Migraine, a primary headache disorder involving a dysfunctional trigeminal vascular system, remains a major debilitating neurological condition impacting many patients' quality of life. Despite the success of multiple new migraine therapies, not all patients achieve significant clinical benefits. The success of CGRP pathway-targeted therapy highlights the importance of translating the mechanistic understanding toward effective therapy. Ongoing research has identified multiple potential mechanisms in migraine signaling and nociception. In this narrative review, we discuss several potential emerging therapeutic targets, including pituitary adenylate cyclase-activating polypeptide (PACAP), adenosine, δ-opioid receptor (DOR), potassium channels, transient receptor potential ion channels (TRP), and acid-sensing ion channels (ASIC). A better understanding of these mechanisms facilitates the discovery of novel therapeutic targets and provides more treatment options for improved clinical care.

Involvement of adenosine signaling pathway in migraine pathophysiology: a systematic review of preclinical studies

Background

Adenosine is a purinergic signaling molecule with a wide range of physiological functions including anti- and pronociceptive properties. Adenosine receptors are expressed in the trigeminovascular system, and adenosine receptor antagonist, caffeine, relieves migraine headache. We performed a systematic review of the literature of preclinical data addressing the role of adenosine in migraine pathophysiology.

Methods

PubMed and EMBASE were searched for pre-clinical studies on the role of adenosine in migraine pathophysiology on September 5^th, 2021.

Results

A total of 2510 studies were screened by title and abstract. Of these, thirteen pre-clinical studies evaluating adenosine, adenosine A1, A2A and A3 receptors were included.

These studies showed that adenosine signaling pathway is involved in controlling vascular tone. Furthermore, electrical stimulation of the trigeminal ganglion modulates the expression of adenosine A₁ and A_2A receptors in the trigeminal ganglion and trigeminal nucleus caudalis implicating adenosine signaling pathway in pain transmission.

Conclusion

Preclinical studies showed that adenosine has a dual effect on vasodilation and trigeminal pain pathway due to different receptor activation, suggesting a possible role of adenosine in migraine pathophysiology. Studies investigating pharmacological characteristics of subtypes of adenosine receptors are needed to further elucidate their role as a potential target for migraine treatment.