Integrative miRNA–mRNA profiling of human epidermis: unique signature of SCN9A painful neuropathy, 2022, Andelic et al.

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Integrative miRNA–mRNA profiling of human epidermis: unique signature of SCN9A painful neuropathy
Andelic, Mirna; Salvi, Erika; Marcuzzo, Stefania; Marchi, Margherita; Lombardi, Raffaella; Cartelli, Daniele; Cazzato, Daniele; Mehmeti, Elkadia; Gelemanovic, Andrea; Paolini, Matilde; Pardo, Carlotta; D’Amato, Ilaria; Hoeijmakers, Janneke G J; Dib-Hajj, Sulayman; Waxman, Stephen G; Faber, Catharina G; Lauria, Giuseppe

Personalized management of neuropathic pain is an unmet clinical need due to heterogeneity of the underlying aetiologies, incompletely understood pathophysiological mechanisms and limited efficacy of existing treatments.

Recent studies on microRNA in pain preclinical models have begun to yield insights into pain-related mechanisms, identifying nociception-related species differences and pinpointing potential drug candidates.

With the aim of bridging the translational gap towards the clinic, we generated a human pain-related integrative miRNA and mRNA molecular profile of the epidermis, the tissue hosting small nerve fibres, in a deeply phenotyped cohort of patients with sodium channel-related painful neuropathy not responding to currently available therapies.

We identified four miRNAs strongly discriminating patients from healthy individuals, confirming their effect on differentially expressed gene targets driving peripheral sensory transduction, transmission, modulation and post-transcriptional modifications, with strong effects on gene targets including NEDD4.

We identified a complex epidermal miRNA–mRNA network based on tissue-specific experimental data suggesting a cross-talk between epidermal cells and axons in neuropathy pain. Using immunofluorescence assay and confocal microscopy, we observed that Nav1.7 signal intensity in keratinocytes strongly inversely correlated with NEDD4 expression that was downregulated by miR-30 family, suggesting post-transcriptional fine tuning of pain-related protein expression.

Our targeted molecular profiling advances the understanding of specific neuropathic pain fine signatures and may accelerate process towards personalized medicine in patients with neuropathic pain.

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The primary goal of this study was to investigate the role of epidermal microenvironment, the forefront of pain initiation processes in sodium channel–related neuropathy (NavNP) patients and to identify new molecular signatures demonstrable by skin biopsy.

For sodium channel signal intensity examination, we used antibody against Nav1.7 [sodium channel] by using free-floating immunofluorescence staining protocol.

Relative expression analysis revealed four miRNAs that were significantly downregulated in NavNP patients compared to HC, surviving the Bonferroni multiple test correction. Two of them, miR-30a-5p [P-value 4.40 × 10−4 , fold change (FC) −4.95] and miR-30d-5p (P-value 3.23 × 10−4 , FC −5.83), belong to the same miRNA family (miR-30 family), whereas miR-203a-3p (P-value 4.40 × 10−4 , FC −3.64) and miR-181a-2-3p (P-value 4.40 × 10−4 , FC −2.21) had no shared origin.

The identification of four downregulated miRNAs (i.e. miR-30a-5p, miR-30d-5p, miR-181a-2-3p, miR-203a-5p) in the epidermis of NavNP patients provides the first robust biomarkers describing the complex pain signalling in targeted human tissue, potentially bridging the gap with the preclinical findings. Indeed, previous studies suggesting the role of the miR-30 family in regulating peripherally expressed VGSC subunits and related pathways focused only on rodent models. We demonstrated, through functional network analysis, that the miR-30 family is required for regulation of expression of wellknown pain therapeutic targets in human epidermis.

Our analysis revealed a correlation between miR-30 family and NEDD4 that is especially interesting in the context of known interactions of NEDD4 with Nav1.7 and other sodium channels. Indeed, the NEDD4 family has been reported to participate, along with other enzymes, in clathrin-mediated Nav1.7 endocytosis and to be essential for Nav1.7 dowregulation. Preclinical studies in models of neuropathic pain have suggested that targeting Nav1.7 regulation through the modulation of this pathway may attenuate neuronal hyperexcitability and nociceptor hypersensitivity.

This study was performed in a small cohort of patients harbouring SCN9A pathogenic variants, thus limiting the generalization of the findings. However, the highly homogeneous characteristics and pain-related genetic background of our study population allowed us to overcome the limitations of the heterogeneity of neuropathic pain patients and of inter-individual differences of miRNA profile. Further miRNA mimicking combined with electrophysiological assay would strengthen the functional role of candidate miRNAs in NavNP patients, which would require patientderived 3D skin model. However, our data support the role of NEDD4 and other genes as major players for modulating neuropathic pain pathways in human skin.

 

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See also Targeting a Peripheral Sodium Channel to Treat Pain (2023, New England Journal of Medicine), which talks about new drugs targeting a similar sodium channel (Nav1.8) with the trial paper being Selective Inhibition of NaV1.8 with VX-548 for Acute Pain (2023, New England Journal of Medicine).

With the advent of the molecular era, it became clear that there are multiple subtypes of sodium channels, all sharing the same overall structure of 24 membrane-spanning segments but with different amino acid sequences and different physiological and pharmacologic properties. The various sodium-channel subtypes, NaV 1.1 to NaV 1.9, have unique expression patterns: each is produced in a cell type–specific manner. For example, the NaV 1.4 channel is produced specifically in skeletal muscle, and the NaV 1.5 channel, in cardiac myocytes.

Because the firing of pain-signaling peripheral neurons depends on the activity of their constituent sodium channels, the discovery of multiple sodium-channel genes raised the possibility of the existence of one or more “peripheral” sodium channels, necessary for the firing of pain-signaling peripheral neurons but with no role in the heart or brain. The blockade of such channels would be expected to alleviate pain without addictive potential (as shown by opiates) and without central side effects. Three subtypes of peripheral sodium channels have been identified : NaV 1.7 (encoded by the gene SCN9A), NaV 1.8 (encoded by SCN10A), and NaV 1.9 (encoded by SCN11A).

large-scale clinical studies of NaV 1.7 blockers, at clinically acceptable doses, have not shown consistent reductions in pain. Whether this reflects differences in drug distribution and pharmacodynamics, the degree of selectivity of NaV1.7 as compared with NaV1.8 blockers, or differences in the types of pain assessed in the different studies is not known.

 

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However, see also Identification and targeting of a unique NaV1.7 domain driving chronic pain (2023, PNAS).