Oxadiazolone bioisosteres of pregabalin and gabapentin.

A series of oxadiazolone bioisosteres of pregabalin 1 and gabapentin 2 were prepared, and several were found to exhibit similar potency for the alpha(2)-delta subunit of voltage-gated calcium channels. Oxadiazolone 9 derived from 2 achieved low brain uptake but was nevertheless active in models of osteoarthritis. The high clearance associated with compound 9 was postulated to be a consequence of efflux by OAT and/or OCT, and was attenuated on co-administration with cimetidine or probenecid.

[3H] pregabalin binding is increased in ipsilateral dorsal horn following chronic constriction injury.

Pregabalin, a 3-substituted analogue of gamma-amino butyric acid has recently been approved for treatment of neuropathic pain. We have investigated the anatomical binding profile of [(3)H] pregabalin following chronic constriction injury (CCI) and compared this with alpha 2 delta 1 subunit expression using in situ hybridisation. We report here that the intensity and distribution pattern of [(3)H] pregabalin binding is altered in the ipsilateral dorsal horn following CCI and this is associated with a corresponding increase in alpha 2 delta 1 mRNA in the ipsilateral dorsal root ganglion (DRG). It is likely that increased DRG mRNA production leads to increased alpha 2 delta 1 protein production and subsequent transport by primary afferents to the dorsal horn. The increased expression of calcium channel subunits and protein in central terminals is interesting, given that abnormal activity within sensory nerves is likely to significantly contribute to the symptomatology of neuropathic pain. The upregulation of pregabalin binding sites in sensory nerve terminals may occur as part of the response to nerve damage in neuropathic pain patients, and therefore, preferential actions of pregabalin at these sites may contribute to its mechanism of action in man.

The Expression of Inflammatory Mediators in Bladder Pain Syndrome.

BACKGROUND: Bladder pain syndrome (BPS) pathology is poorly understood. Treatment strategies are empirical, with limited efficacy, and affected patients have diminished quality of life. OBJECTIVE: We examined the hypothesis that inflammatory mediators within the bladder contribute to BPS pathology. DESIGN, SETTING, AND PARTICIPANTS: Fifteen women with BPS and 15 women with stress urinary incontinence without bladder pain were recruited from Cork University Maternity Hospital from October 2011 to October 2012. During cystoscopy, 5-mm bladder biopsies were taken and processed for gene expression analysis. The effect of the identified genes was tested in laboratory animals. OUTCOME MEASURES AND STATISTICAL ANALYSIS: We studied the expression of 96 inflammation-related genes in diseased and healthy bladders. We measured the correlation between genes and patient clinical profiles using the Pearson correlation coefficient. RESULTS AND LIMITATIONS: Analysis revealed 15 differentially expressed genes, confirmed in a replication study. FGF7 and CCL21 correlated significantly with clinical outcomes. Intravesical CCL21 instillation in rats caused increased bladder excitability and increased c-fos activity in spinal cord neurons. CCL21 atypical receptor knockout mice showed significantly more c-fos upon bladder stimulation with CCL21 than wild-type littermates. There was no change in FGF7-treated animals. The variability in patient samples presented as the main limitation. We used principal component analysis to identify similarities within the patient group. CONCLUSIONS: Our study identified two biologically relevant inflammatory mediators in BPS and demonstrated an increase in nociceptive signalling with CCL21. Manipulation of this ligand is a potential new therapeutic strategy for BPS. PATIENT SUMMARY: We compared gene expression in bladder biopsies of patients with bladder pain syndrome (BPS) and controls without pain and identified two genes that were increased in BPS patients and correlated with clinical profiles. We tested the effect of these genes in laboratory animals, confirming their role in bladder pain. Manipulating these genes in BPS is a potential treatment strategy.

The discovery and development of analgesics: new mechanisms, new modalities.

Despite intensive research into pain mechanisms and significant investment in research and development, the majority of analgesics available to prescribers and patients are based on mechanistic classes of compounds that have been known for many years. With considerable ingenuity and innovation, researchers continue to make the best of the mechanistic approaches available, with novel formulations, routes of administration, and combination products. Here we review some of the mechanisms and modalities of analgesics that have recently entered into clinical development, which, coupled with advances in the understanding of the pathophysiology of chronic pain, will hopefully bring the promise of new therapeutics that have the potential to provide improved pain relief for those many patients whose needs remain poorly met.

Identification of the alpha2-delta-1 subunit of voltage-dependent calcium channels as a molecular target for pain mediating the analgesic actions of pregabalin.

Neuropathic pain is a debilitating condition affecting millions of people around the world and is defined as pain that follows a lesion or dysfunction of the nervous system. This type of pain is difficult to treat, but the novel compounds pregabalin (Lyrica) and gabapentin (Neurontin) have proven clinical efficacy. Unlike traditional analgesics such as nonsteroidal antiinflammatory drugs or narcotics, these agents have no frank antiinflammatory actions and no effect on physiological pain. Although extensive preclinical studies have led to a number of suggestions, until recently their mechanism of action has not been clearly defined. Here, we describe studies on the analgesic effects of pregabalin in a mutant mouse containing a single-point mutation within the gene encoding a specific auxiliary subunit protein (alpha2-delta-1) of voltage-dependent calcium channels. The mice demonstrate normal pain phenotypes and typical responses to other analgesic drugs. We show that the mutation leads to a significant reduction in the binding affinity of pregabalin in the brain and spinal cord and the loss of its analgesic efficacy. These studies show conclusively that the analgesic actions of pregabalin are mediated through the alpha2-delta-1 subunit of voltage-gated calcium channels and establish this subunit as a therapeutic target for pain control.