Polymorphism in the SCN9A voltage-gated sodium channel gene associated with interstitial cystitis/bladder pain syndrome

Genetic polymorphisms associated with urinary tract infection in children and adults: a systematic review and meta-analysis

INTRODUCTION

The lifetime risk of urinary tract infection is known from first-degree relative studies to be highly heritable. Associations have also been observed across the life course from pediatric urinary tract infection to recurrent urinary tract infection in adulthood, suggesting lifelong susceptibility factors. Candidate gene studies and genome-wide association studies have tested for genetic associations of urinary tract infection; however, no contemporary systematic synthesis of studies is available.

OBJECTIVE

We conducted a systematic review to identify all genetic polymorphisms tested for an association with urinary tract infection in children and adults; and to assess their strength, consistency, and risk of bias among reported associations.

DATA SOURCES AND STUDY ELIGIBILITY CRITERIA

PubMed, HuGE Navigator and Embase were searched from January 1, 2005 to November 16, 2023, using a combination of genetic and phenotype key words.

STUDY APPRAISAL AND SYNTHESIS METHODS

Fixed and random effects meta-analyses were conducted using codominant models of inheritance in metan. The interim Venice criteria were used to assess their credibility of pooled associations.

RESULTS

After removing 451 duplicates, 1821 studies reports were screened, with 106 selected for full-text review, 22 were included in the meta-analysis (7 adult studies and 15 pediatric studies). Our meta-analyses demonstrated significant pooled associations for pediatric urinary tract infection with variation in CXCR1, IL8, TGF, TLR4 and VDR; all of which have plausible roles in the pathogenesis of urinary tract infection. Our meta-analyses also demonstrated a significant pooled association for adult urinary tract infection with variation in CXCR1. All significant pooled associations were graded according to their epidemiological credibility, sample sizes, heterogeneity between studies, and risk of bias.

CONCLUSION

This systematic review provides a current synthesis of the known genetic architecture of urinary tract infection in childhood and adulthood; and should provide important information for researchers analysing future genetic association studies. Although, overall, the credibility of pooled associations was weak, the consistency of findings for rs2234671 single nucleotide polymorphisms of CXCR1 in both populations suggest a key role in the urinary tract infection pathogenesis.

No Association of Polymorphisms in Nav1.7 or Nerve Growth Factor Receptor Genes with Trigeminal Neuralgia

OBJECTIVE

Trigeminal neuralgia is defined as a sudden severe shock-like pain within the distribution of the trigeminal nerve. Pain is a subjective experience that is influenced by gender, culture, environment, psychological traits, and genes. Sodium channels and nerve growth factor play important roles in the transmission of nociceptive signals and pain. The aim of this study was to investigate the occurrence of Nav1.7 sodium channel and nerve growth factor receptor TrkA gene polymorphisms (SCN9A/rs6746030 and NTRK1/rs633, respectively) in trigeminal neuralgia patients.

METHODS

Ninety-six subjects from pain specialty centers in the southeastern region of Brazil were divided into 2 groups: 48 with classical trigeminal neuralgia diagnosis and 48 controls. Pain was evaluated using the visual analog scale and multidimensional McGill Pain Questionnaire. Genomic DNA was obtained from oral swabs in all individuals and was analyzed by real-time polymerase chain reaction.

RESULTS

No association was observed between evaluated polymorphisms and trigeminal neuralgia. For allele analyses, patients and controls had similar frequencies for both genes. Genotype distribution or allele frequencies of polymorphisms analyzed here did not correlate to pain scores.

CONCLUSIONS

Although no association of evaluated polymorphisms and trigeminal neuralgia diagnosis or pain severity was observed, our data do not exclude the possibility that other genotypes affecting the expression of Nav1.7 or TrkA are associated with the disease. Further studies should investigate distinct genetic polymorphisms and epigenetic factors that may be important in expression of these molecules.

Sporadic Erythromelalgia Associated with a Homozygous Carrier of Common Missense Polymorphism in SCN9A Gene Coding for NaV1.7 Voltage-gated Sodium Channel

A 68-year-old female with a history of sporadic type and presumably secondary erythromelalgia with chronic intractable pain presented for foot surgery. The procedure was performed with combined general anesthesia and regional anesthesia consisting of the placement of a popliteal pain catheter for postoperative pain management. Subsequent whole-genome sequencing revealed that the patient was a homozygous carrier of the common missense mutation in the SCN9A gene coding for voltage-gated sodium channel (NaV1.7) - dbSNP rs6746030 (R1150W). The occurrence of this single nucleotide polymorphism (SNP) was previously suggested not to be associated with erythromelalgia but rather thought to be part of quantitative changes in the pain threshold in different cohorts of patients. The placement of the pain catheter, although controversial in patients with erythromelalgia, provided effective postoperative pain relief without any side effects.

Single nucleotide polymorphism analysis in interstitial cystitis/painful bladder syndrome

INTRODUCTION

Interstitial Cystitis (IC) is a chronic condition diagnosed based on the presence of symptoms, such as suprapubic/ pelvic pain, pressure or discomfort in association with urgency and increased urinary frequency. Confusable diseases must be excluded. However, there is no objective test or marker to establish the presence of the disease. Diagnosis and patient management is often difficult, given the poor understanding of IC pathogenesis and its unknown etiology and genetics. As an attempt to find biomarkers related to IC, we assessed the association between 20 selected single nucleotide polymorphism (SNPs) with IC and pain severity.

OBJECTIVES

To assess the presence of SNPs in IC patients' blood samples and correlate them with the disease and chronic pain condition.

METHODS

A case-control study was conducted. We selected 34 female patients with IC diagnosed according to NIDDK criteria and 23 patients in the control group (previously healthy women with only stress urinary incontinence). IC patients were allocated into two groups according to reported chronic pain severity. We selected the following SNPs for analysis: rs1800871, rs1800872, rs1800896, rs1800471, rs1800629, rs361525, rs1800497, rs6311, rs6277, rs6276, rs6313, rs2835859, rs11127292, rs2243248, rs6887695, rs3212227, rs1799971, rs12579350, rs3813034, and rs6746030. Genotyping was performed by real-time PCR (q-PCR).

RESULTS

The polymorphic allele of SNP rs11127292 exhibited a higher frequency in subjects with IC than in controls (p:0.01). The polymorphic allele of SNP rs6311 was more frequent in patients with severe pain (p:0.03). The frequency of the wild-type allele of SNP rs1799971 was higher in patients with mild to moderate pain (p:0.04).

CONCLUSION

The results indicated differences in SNP frequency among subjects, suggesting that SNPs could serve either as a marker of IC or as a marker of pain severity in IC patients. The study showed promising results regarding IC and polymorphism associations. These associations have not been previously reported.

Voltage-gated sodium channels: (NaV )igating the field to determine their contribution to visceral nociception

Chronic visceral pain, altered motility and bladder dysfunction are common, yet poorly managed symptoms of functional and inflammatory disorders of the gastrointestinal and urinary tracts. Recently, numerous human channelopathies of the voltage-gated sodium (NaV ) channel family have been identified, which induce either painful neuropathies, an insensitivity to pain, or alterations in smooth muscle function. The identification of these disorders, in addition to the recent utilisation of genetically modified NaV mice and specific NaV channel modulators, has shed new light on how NaV channels contribute to the function of neuronal and non-neuronal tissues within the gastrointestinal tract and bladder. Here we review the current pre-clinical and clinical evidence to reveal how the nine NaV channel family members (NaV 1.1-NaV 1.9) contribute to abdominal visceral function in normal and disease states.

Visceral and somatic pain modalities reveal NaV 1.7-independent visceral nociceptive pathways

KEY POINTS

Voltage-gated sodium channels play a fundamental role in determining neuronal excitability. Specifically, voltage-gated sodium channel subtype Na_V 1.7 is required for sensing acute and inflammatory somatic pain in mice and humans but its significance in pain originating from the viscera is unknown. Using comparative behavioural models evoking somatic and visceral pain pathways, we identify the requirement for Na_V 1.7 in regulating somatic (noxious heat pain threshold) but not in visceral pain signalling. These results enable us to better understand the mechanisms underlying the transduction of noxious stimuli from the viscera, suggest that the investigation of pain pathways should be undertaken in a modality-specific manner and help to direct drug discovery efforts towards novel visceral analgesics.

ABSTRACT

Voltage-gated sodium channel Na_V 1.7 is required for acute and inflammatory pain in mice and humans but its significance for visceral pain is unknown. Here we examine the role of Na_V 1.7 in visceral pain processing and the development of referred hyperalgesia using a conditional nociceptor-specific Na_V 1.7 knockout mouse (Na_V 1.7^Nav1.8 ) and selective small-molecule Na_V 1.7 antagonist PF-5198007. Na_V 1.7^Nav1.8 mice showed normal nociceptive behaviours in response to intracolonic application of either capsaicin or mustard oil, stimuli known to evoke sustained nociceptor activity and sensitization following tissue damage, respectively. Normal responses following induction of cystitis by cyclophosphamide were also observed in both Na_V 1.7^Nav1.8 and littermate controls. Loss, or blockade, of Na_V 1.7 did not affect afferent responses to noxious mechanical and chemical stimuli in nerve-gut preparations in mouse, or following antagonism of Na_V 1.7 in resected human appendix stimulated by noxious distending pressures. However, expression analysis of voltage-gated sodium channel α subunits revealed Na_V 1.7 mRNA transcripts in nearly all retrogradely labelled colonic neurons, suggesting redundancy in function. By contrast, using comparative somatic behavioural models we identify that genetic deletion of Na_V 1.7 (in Na_V 1.8-expressing neurons) regulates noxious heat pain threshold and that this can be recapitulated by the selective Na_V 1.7 antagonist PF-5198007. Our data demonstrate that Na_V 1.7 (in Na_V 1.8-expressing neurons) contributes to defined pain pathways in a modality-dependent manner, modulating somatic noxious heat pain, but is not required for visceral pain processing, and advocate that pharmacological block of Na_V 1.7 alone in the viscera may be insufficient in targeting chronic visceral pain.

The Neuropsychoanalytic Approach: Using Neuroscience as the Basic Science of Psychoanalysis

Neuroscience was the basic science behind Freud's psychoanalytic theory and technique. He worked as a neurologist for 20 years before being aware that a new approach to understand complex diseases, namely the hysterias, was needed. Solms coined the term neuropsychoanalysis to affirm that neuroscience still belongs in psychoanalysis. The neuropsychoanalytic field has continued Freud's original ideas as stated in 1895. Developments in psychoanalysis that have been created or revised by the neuropsychoanalysis movement include pain/relatedness/opioids, drive, structural model, dreams, cathexis, and dynamic unconscious. Neuroscience has contributed to the development of new psychoanalytic theory, such as Bazan's (2011) description of anxiety driven by unconscious intentions or “phantoms.” Results of adopting the “dual aspect monism” approach of idiographic psychoanalytic clinical observation combined with nomothetic investigation of related human phenomena include clarification and revision of theory, restoration of the scientific base of psychoanalysis, and improvement of clinical treatments. By imbricating psychoanalytic thinking with neuroscience, psychoanalysts are also positioned to make contributions to neuroscience research. Freud's original Project for a Scientific Psychology/Psychology for Neurologists can be carried forward in a way that moves psychoanalysis into the twenty-first century as a core contemporary science (Kandel, 1999). Neuroscience as the basic science of psychoanalysis both improves the field, and enhances its scientific and cultural status.

Seven novel modulators of the analgesic target NaV 1.7 uncovered using a high-throughput venom-based discovery approach

BACKGROUND AND PURPOSE

Chronic pain is a serious worldwide health issue, with current analgesics having limited efficacy and dose-limiting side effects. Humans with loss-of-function mutations in the voltage-gated sodium channel NaV 1.7 (hNaV 1.7) are indifferent to pain, making hNaV 1.7 a promising target for analgesic development. Since spider venoms are replete with NaV channel modulators, we examined their potential as a source of hNaV 1.7 inhibitors.

EXPERIMENTAL APPROACH

We developed a high-throughput fluorescent-based assay to screen spider venoms against hNaV 1.7 and isolate 'hit' peptides. To examine the binding site of these peptides, we constructed a panel of chimeric channels in which the S3b-S4 paddle motif from each voltage sensor domain of hNaV 1.7 was transplanted into the homotetrameric KV 2.1 channel.

KEY RESULTS

We screened 205 spider venoms and found that 40% contain at least one inhibitor of hNaV 1.7. By deconvoluting 'hit' venoms, we discovered seven novel members of the NaSpTx family 1. One of these peptides, Hd1a (peptide μ-TRTX-Hd1a from venom of the spider Haplopelma doriae), inhibited hNaV 1.7 with a high level of selectivity over all other subtypes, except hNaV 1.1. We showed that Hd1a is a gating modifier that inhibits hNaV 1.7 by interacting with the S3b-S4 paddle motif in channel domain II. The structure of Hd1a, determined using heteronuclear NMR, contains an inhibitor cystine knot motif that is likely to confer high levels of chemical, thermal and biological stability.

CONCLUSION AND IMPLICATIONS

Our data indicate that spider venoms are a rich natural source of hNaV 1.7 inhibitors that might be useful leads for the development of novel analgesics.

Multiple roles for NaV1.9 in the activation of visceral afferents by noxious inflammatory, mechanical, and human disease-derived stimuli

Chronic visceral pain affects millions of individuals worldwide and remains poorly understood, with current therapeutic options constrained by gastrointestinal adverse effects. Visceral pain is strongly associated with inflammation and distension of the gut. Here we report that the voltage-gated sodium channel subtype NaV1.9 is expressed in half of gut-projecting rodent dorsal root ganglia sensory neurons. We show that NaV1.9 is required for normal mechanosensation, for direct excitation and for sensitization of mouse colonic afferents by mediators from inflammatory bowel disease tissues, and by noxious inflammatory mediators individually. Excitatory responses to ATP or PGE2 were substantially reduced in NaV1.9(-/-) mice. Deletion of NaV1.9 substantially attenuates excitation and subsequent mechanical hypersensitivity after application of inflammatory soup (IS) (bradykinin, ATP, histamine, PGE2, and 5HT) to visceral nociceptors located in the serosa and mesentery. Responses to mechanical stimulation of mesenteric afferents were also reduced by loss of NaV1.9, and there was a rightward shift in stimulus-response function to ramp colonic distension. By contrast, responses to rapid, high-intensity phasic distension of the colon are initially unaffected; however, run-down of responses to repeat phasic distension were exacerbated in NaV1.9(-/-) afferents. Finally colonic afferent activation by supernatants derived from inflamed human tissue was greatly reduced in NaV1.9(-/-) mice. These results demonstrate that NaV1.9 is required for persistence of responses to intense mechanical stimulation, contributes to inflammatory mechanical hypersensitivity, and is essential for activation by noxious inflammatory mediators, including those from diseased human bowel. These observations indicate that NaV1.9 represents a high-value target for development of visceral analgesics.

Pharmacogenetics of chronic pain and its treatment

This paper reviews the impact of genetic variability of drug metabolizing enzymes, transporters, receptors, and pathways involved in chronic pain perception on the efficacy and safety of analgesics and other drugs used for chronic pain treatment. Several candidate genes have been identified in the literature, while there is usually only limited clinical evidence substantiating for the penetration of the testing for these candidate biomarkers into the clinical practice. Further, the pain-perception regulation and modulation are still not fully understood, and thus more complex knowledge of genetic and epigenetic background for analgesia will be needed prior to the clinical use of the candidate genetic biomarkers.

Nature and nurture of human pain

Humans are very different when it comes to pain. Some get painful piercings and tattoos; others can not stand even a flu shot. Interindividual variability is one of the main characteristics of human pain on every level including the processing of nociceptive impulses at the periphery, modification of pain signal in the central nervous system, perception of pain, and response to analgesic strategies. As for many other complex behaviors, the sources of this variability come from both nurture (environment) and nature (genes). Here, I will discuss how these factors contribute to human pain separately and via interplay and how epigenetic mechanisms add to the complexity of their effects.