A247 ACTIVATION OF VISCERAL AFFERENT NEURONS INVOLVED IN NOCICEPTION BY A BACTERIUM ASSOCIATED WITH INFLAMMATORY BOWEL DISEASE
Bibliographic record
Abstract
Abstract Background Inflammatory bowel disease (IBD) is characterized by chronic relapsing inflammation of the gastrointestinal tract. Severe abdominal pain is a common symptom of IBD, yet effective pain treatments are limited. Proteolytic activity is elevated in IBD compared to healthy individuals. Recently, protease production by the gut bacterium Bacteroides vulgatus has been correlated with the severity of IBD. Aims Since proteases acting on protease-activated receptor 2 (PAR-2) can activate visceral pain pathways, we test the hypothesis that mediators from B. vulgatus activate visceral pain pathways and can directly activate dorsal root ganglia (DRG) neurons, altering pain signalling. Methods The effects of B. vulgatus ATCC 8482 supernatant or brain heart infusion (BHI) growth media on nociceptive neurons were assessed using ex-vivo single-unit afferent nerve recordings from C57bl/6 mouse colons. To further examine cellular mechanisms, Ca2+ imaging was performed on dissociated DRG neurons following the superfusion of B. vulgatus culture supernatant. As TRPV1 is an ion channel expressed mainly on nociceptive neurons, the effect of B vulgatus culture supernatant on Ca2+ influx in response to the TRPV1 agonist capsaicin was also quantified. “N” represents mice, while “n” represents single afferent units or DRG neurons. Results Perfusion of B. vulgatus supernatant (1:20) through the lumen of murine colons significantly increased basal firing frequency by 50% (p < 0.001, N = 8, n = 38) and mechanosensitivity of colonic afferent axons by 48% (p < 0.05, N = 8). Interestingly, only the putative nociceptor high-threshold units were activated upon perfusion of this bacterial supernatant (p < 0.01, N = 8, n = 13), while the wide-dynamic range units were unaffected (p > 0.05, N = 8, n = 30). The BHI growth media did not alter basal activity (p > 0.05, N = 6, n = 23) or afferent nerve mechanosensitivity (p > 0.05, N = 6). Superfusion of B. vulgatus supernatant (1:100) increased intracellular [Ca2+] by 16% (p < 0.0001, N= 7, n = 51). Furthermore, exposure to the B. vulgatus supernatant significantly elevated Ca2+ influx in response to the TRPV1 agonist capsaicin (100 nM; p < 0.0001, n = 77, N = 7), while the BHI media did not alter intracellular [Ca2+] in response to capsaicin (p > 0.05, n = 66, N = 7). Conclusions Mediators released by Bacteroides vulgatus can activate visceral afferent nerves involved in nociception. Additionally, B. vulgatus can directly modulate DRG neuronal Ca2+ homeostasis and sensitize TRPV1 in these neurons. Future studies will explore whether proteases are responsible. Funding Agencies CIHR
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".