Search

Inflammation of the distal bowel is often associated with abdominal pain and hypersensitivity, but whether and which colorectal afferents contribute to the hypersensitivity is unknown. Using a mouse model of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis, we investigated colorectal hypersensitivity following intracolonic TNBS and associated changes in colorectum and afferent functions. C57BL/6 mice were treated intracolonically with TNBS or saline. Visceromotor responses to colorectal distension (15–60 mmHg) were recorded over 8 wk in TNBS- and saline-treated (control) mice. In other mice treated with TNBS or saline, colorectal inflammation was assessed by myeloperoxidase assay and immunohistological staining. In vitro single-fiber recordings were conducted on both TNBS and saline-treated mice to assess colorectal afferent function. Mice exhibited significant colorectal hypersensitivity through day 14 after TNBS treatment that resolved by day 28 with no resensitization through day 56. TNBS induced a neutrophil- and macrophage-based colorectal inflammation as well as loss of nerve fibers, all of which resolved by days 14–28. Single-fiber recordings revealed a net increase in afferent drive from stretch-sensitive colorectal afferents at day 14 post-TNBS and reduced proportions of mechanically insensitive afferents (MIAs) at days 14–28. Intracolonic TNBS-induced colorectal inflammation was associated with the development and recovery of hypersensitivity in mice, which correlated with a transient increase and recovery of sensitization of stretch-sensitive colorectal afferents and MIAs. These results indicate that the development and maintenance of colorectal hypersensitivity following inflammation are mediated by peripheral drive from stretch-sensitive colorectal afferents and a potential contribution from MIAs.

STAT3 overexpression has been detected in several cancers including head and neck squamous cell carcinoma (HNSCC). Previous studies using intratumoral administration of a STAT3 decoy oligonucleotide that abrogates STAT3-mediated gene transcription in preclinical cancer models have demonstrated antitumor efficacy. This study was conducted to observe the toxicity and biologic effects of the STAT3 decoy in a non-human primate model, in anticipation of initiating a clinical trial in HNSCC patients.Three study groups (two monkeys/sex/group) were administered a single intramuscular injection of low dose of STAT3 decoy (0.8 mg total dose/monkey), high dose of STAT3 decoy (3.2 mg total dose/monkey) or vehicle control (PBS alone) on day 1 and necropsies were performed on days 2 and 15 (one monkey/sex/group/day). Low and high doses of the decoy were administered in the muscle in a volume of 0.9 ml. Tissue and blood were harvested for toxicology and biologic analyses.Upon observation, the STAT3 decoy-treated animals exhibited behavior that was similar to the vehicle control group. Individual animal body weights remained within 1% of pretreatment weights throughout the study. Hematological parameters were not significantly different between the control and the treatment groups. Clinical chemistry fluctuations were considered within normal limits and were not attributed to the STAT3 decoy. Assessment of complement activation breakdown product (Bb) levels demonstrated no activation of the alternative pathway of complement in any animal at any dose level. At necropsy, there were no gross or microscopic findings attributed to STAT3 decoy in any organ examined. STAT3 target gene expression at the injection site revealed decreased Bcl-X(L) and cyclin D1 expression levels in the animals treated with high dose of STAT3 decoy compared to the animals injected with low dose of STAT3 decoy or the vehicle as control.Based on these findings, the no-observable-adverse-effect-level (NOAEL) was greater than 3.2 mg/kg when administered as a single dose to male and female Cynomolgus monkeys. Plans are underway to test the safety and biologic effects of intratumoral administration of the STAT3 decoy in HNSCC patients.

Afferent input contributes significantly to the pain and colorectal hypersensitivity that characterize irritable bowel syndrome. In the present study, we investigated the contributions of mechanically sensitive and mechanically insensitive afferents (MIAs; or silent afferents) to colorectal hypersensitivity. The visceromotor response to colorectal distension (CRD; 15–60 mmHg) was recorded in mice before and for weeks after intracolonic treatment with zymosan or saline. After CRD tests, the distal colorectum with the pelvic nerve attached was removed for single-fiber electrophysiological recordings. Colorectal afferent endings were located by electrical stimulation and characterized as mechanosensitive or not by blunt probing, mucosal stroking, and circumferential stretch. Intracolonic zymosan produced persistent colorectal hypersensitivity (>24 days) associated with brief colorectal inflammation. Pelvic nerve muscular-mucosal but not muscular mechanosensitive afferents recorded from mice with colorectal hypersensitivity exhibited persistent sensitization. In addition, the proportion of MIAs (relative to control) was significantly reduced from 27% to 13%, whereas the proportion of serosal afferents was significantly increased from 34% to 53%, suggesting that MIAs acquired mechanosensitivity. PGP9.5 immunostaining revealed no significant loss of colorectal nerve fiber density, suggesting that the reduction in MIAs is not due to peripheral fiber loss after intracolonic zymosan. These results indicate that colorectal MIAs and sensitized muscular-mucosal afferents that respond to stretch contribute significantly to the afferent input that sustains hypersensitivity to CRD, suggesting that targeted management of colorectal afferent input could significantly reduce patients' complaints of pain and hypersensitivity.