The Voltage-Gated Calcium Channel α2δ Subunit in Neuropathic Pain

Spinal neuron-glial crosstalk and ion channel dysregulation in diabetic neuropathic pain

Diabetic neuropathic pain (DNP) is one of the most prevalent complications of diabetes, characterized by a high global prevalence and a substantial affected population with limited effective therapeutic options. Although DNP is closely associated with hyperglycemia, an increasing body of research suggests that elevated blood glucose levels are not the sole inducers of DNP. The pathogenesis of DNP is intricate, involving the release of inflammatory mediators, alterations in synaptic plasticity, demyelination of nerve fibers, and ectopic impulse generation, yet the precise mechanisms remain to be elucidated. The spinal dorsal horn coordinates dynamic interactions between peripheral and central pain pathways, wherein dorsal horn neurons, microglia, and astrocytes synergize with Schwann cell-derived signals to process nociceptive information flow. Abnormally activated neurons can alter signal transduction by modifying the local microenvironment, compromising myelin integrity, and diminishing trophic support, leading to neuronal sensitization and an amplifying effect on peripheral pain signals, which in turn triggers neuropathic pain. Ion channels play a pivotal role in signal conduction, with the modulation of sodium, potassium, and calcium channels being particularly crucial for the regulation of pain signals. In light of the rising incidence of diabetes and the current scarcity of effective DNP treatments, a thorough investigation into the interactions between neurons and glial cells, especially the mechanisms of ion channel function in DNP, is imperative for identifying potential drug targets, developing novel therapeutic strategies, and thereby enhancing the prospects for DNP management.

CKD-Associated Pruritus is Associated with Greater Use of Antidepressants and Anti-pruritus Medications

INTRODUCTION

Chronic kidney disease-associated pruritus (CKD-aP) is a common, yet underdiagnosed condition among patients on hemodialysis. Considering the lack of established treatment pathways, we sought to evaluate the use of antidepressant, systemic antihistamines, or gabapentinoid medications among patients with CKD-aP in the year following pruritus assessment.

METHODS

We included 6209 patients on hemodialysis in the analysis. We retrospectively extracted clinical and patient-reported data from electronic health records. The intensity of CKD-aP was assessed by KDQOL-36 and 5-D Itch questionnaires. Prescription of antidepressant, antihistamine, and gabapentinoids was ascertained by the occurrence of a relevant active medical order in patients' medical records.

RESULTS

We observed a consistent and graded association between the severity of CKD-aP and the use of antidepressant, systemic antihistamines, and gabapentinoid medications. This association remained consistent and intensified over the duration of the year after pruritus screening. This trend was robust even after accounting for potential confounding factors.

CONCLUSIONS

Patterns of antipruritic medication use in a cohort of patients with CKD-aP was identified and the frequent use of off-label treatments in the absence of approved therapies was highlighted. These observations reflect clinical practices aimed at managing severe pruritus but do not imply a causal relationship between the medications and pruritus severity. Even though we cannot exclude the possibility that these drugs have been prescribed to treat medical conditions warranting their use, previous evidence suggested that doctors may also use such medications in an attempt to buffer CKD-aP. These findings underline the importance of further elucidating current treatment strategies adopted in clinical practice to address CKD-aP.

Quantification of crisugabalin (HSK16149) in biological matrix by LC-MS/MS method: An application to rat pharmacokinetic and tissue distribution studies

Crisugabalin (HSK16149), a novel VGCC α2δ ligand, has been approved for the treatment of adult diabetic peripheral neuropathic pain (DPNP) and postherpetic neuralgia (PHN). In this study, an LC-MS/MS method was developed for the determination of crisugabalin in rat plasma and tissues homogenate. Samples were extracted by protein precipitation and separated on a Hypersil GOLD aQ column with methanol and 2 mM ammonium acetate in water containing 0.1 % formic acid as mobile phase. Crisugabalin and its internal standard HSK7891 were ionized by electrospray ionization source and detected by multiple reaction monitoring with transitions of m/z 210.9 → 134.4 and m/z 246.0 → 129.3. Over the range of 0.0100-10.0 μg/mL, the selectivity, linearity, precision and accuracy, matrix effect, stability, recovery and dilution integrity of crisugabalin were validated in rat plasma. Validation was also performed in rat liver homogenate at concentrations ranging from 0.0200-20.0 μg/g. The method was then successfully applied to determine the pharmacokinetics and tissue distribution of crisugabalin. In rats, orally administered crisugabalin was completely and rapidly absorbed with a peak time of about 0.57 h, and was mainly distributed to kidney, bladder and liver tissues. Crisugabalin exhibited linear pharmacokinetics over the oral dose range of 3-30 mg/kg.

A nociceptive-nociplastic spectrum of myofascial orofacial pain: insights from neuronal ion channel studies

Myofascial orofacial pain, traditionally viewed as a nociceptive pain condition, also exhibits characteristics consistent with nociplastic pain-pain arising from altered nociception without clear evidence of tissue damage. Evidence supporting myofascial orofacial pain as nociplastic pain includes clinical observations of central sensitisation in patients, even in the absence of visible inflammation. Sensitisation is characterised by heightened responsiveness of nociceptive neurons to normal stimuli or activation by normally subthreshold stimuli, either in the peripheral or central nervous system. It is linked to maladaptive neuroplastic changes, including increased functional potentiation and altered expression of neuronal ion channels, receptors and neurotransmitters. This mini-review presents insights from existing evidence regarding altered nociception and its relation to changes in the expression of neuronal ion channels in myofascial orofacial pain. Increased expression of transient receptor potential (TRP) vanilloid 1 channels (TRPV1), TRPV4, TRP ankyrin 1 channels (TRPA1), Piezo2 channels, P2X3 purinergic receptors, N-Methyl-D-Aspartate (NMDA) receptors and voltage-gated calcium channels in the trigeminal ganglion of rodents has been observed in association with myofascial orofacial pain. This evidence highlights the role of neuronal ion channels in the pathophysiology of myofascial orofacial pain and supports the involvement of nociplastic mechanisms.