Involvement of JAK-STAT signaling/function after cyclophosphamide-induced bladder inflammation in female rats

Abstract

The role of JAK-STAT signaling in urinary bladder inflammation and referred somatic sensitivity has not been addressed. The contribution of JAK-STAT signaling pathways in CYP-induced bladder hyperreflexia and referred somatic hypersensitivity was determined in CYPtreated rats using a JAK2 inhibitor, AG490. Acute (4 h; 150 mg/kg ip), intermediate (48 h; 150 mg/kg ip), or chronic (75 mg/kg ip, once every 3 days for 10 days) cystitis was induced in adult, female Wistar rats with CYP treatment. Phosphorylation status of STAT-3 was increased in urinary bladder after CYP-induced cystitis (4 h, 48 h, chronic). Blockade of JAK2 with AG490 (5-15 mg/kg ip or intravesical) significantly (P Յ 0.05) reduced bladder hyperreflexia and hind paw sensitivity in CYP-treated rats. These studies demonstrate a potential role for JAK-STAT signaling pathways in bladder hyperreflexia and referred pain induced by CYP-induced bladder inflammation. somatic sensitivity; bladder hyperreflexia; cystometry; AG490 CLINICAL SYMPTOMS OF INTERSTITIAL CYSTITIS (IC)/painful bladder syndrome (PBS) include bladder and/or pelvic pain, urinary frequency, and urgency (17, 44). The pathophysiologic mechanisms of IC/PBS are not fully understood but current research hypotheses include bladder urothelial dysfunction, mast cell activation and recruitment, and neurogenic inflammation (41). Potential mediators of urinary bladder inflammation are numerous and include cytokines (19,36,40), chemokines (55), neuropeptides (5, 49), neuroactive compounds (4), and growth factors (51, 54,56). Of these mediators, a number of cytokines have been implicated in animal models of urinary bladder inflammation and in IC/PBS human studies. For example, interleukin-6 (IL-6) expression is markedly increased in urine of IC/PBS patients (19,36). Bladder inflammation in rats and mice induced by cyclophosphamide (CYP) increased transcript and protein expression in urinary bladder of several cytokines, including 40). Furthermore, the IL-6 cytokine family member leukemia inhibitory factor (LIF) is also regulated at the transcript and protein levels in the urinary bladder by CYP-induced cystitis and increased protein expression is exhibited in the urothelium, detrusor smooth muscle, and in nerve fibers of the suburothelial plexus (7) with CYP-induced cystitis.LIF and IL-6 receptor interactions, among others (3, 12, 14, 21, 30), induce transphosphorylation of the receptor-associated Janus-activated kinases (JAK), which in turn leads to phosphorylation of the downstream signal transducer and activator of transcription (STAT) family of transcription factors (JAK-STAT pathway) (18,30). The IL-6 family of cytokines also activates mitogen-activated protein kinase (MAPK) signaling pathways and associated transcription factors (21). Inhibition of JAK-STAT3 signaling pathway by AG490, a member of the tyrphostin family of tyrosine kinase inhibitors, reduces inflammatory changes in bronchial epithelial cells (26) and neuropathic pain stemming from peripheral nerve injury (14). Previous studies (11...

Anti-hyperalgesic effects of AG490, a Janus kinase inhibitor, in a rat model of inflammatory pain

“…Additionally, in the mechanical hyperalgesia test, AG490 treatment increased the PWT at all doses tested; however, this effect was not statistically significant. Therefore, we speculate that AG490 is more effective at reducing mechanical allodynia as measured in previous studies (5,6), than for reducing mechanical hyperalgesia, as shown in the present study. It is also possible that differences in animal model, and route and dose of AG490 administration influence the effects of AG490 on the response to mechanical stimuli.…”

“…in a volume of 100 µl. As reported earlier, the in vivo pharmacological effects of AG490 were observed 4 h after treatment (5,6). Thus, the behavioral tests were performed before (baseline assessment) and 4 h after treatment.…”

“…The thermal hyperalgesia test was performed using a plantar analgesia instrument (IITC Life Science, Woodland Hills, CA, USA), as described previously (6). Briefly, rats were acclimated to the Plexiglas chambers for 30 min prior to testing.…”

Repeated variate stress in male rats induces increased voiding frequency, somatic sensitivity, and urinary bladder nerve growth factor expression

“…On day 8, 24 h after presentation of the last stressor, a lower midline abdominal incision was made under general anesthesia with 2-3% isoflurane using aseptic techniques (16,33,40,68). One end of polyethylene tubing (PE-50; Clay Adams, Parsippany, NJ) was flared with a flame and inserted in the dome of the bladder and secured in place with a 6-0 nylon purse-string suture (16,33,40,68).…”

“…One end of polyethylene tubing (PE-50; Clay Adams, Parsippany, NJ) was flared with a flame and inserted in the dome of the bladder and secured in place with a 6-0 nylon purse-string suture (16,33,40,68). The distal end of the tubing was tunneled subcutaneously to the back of the neck where it was buried in an incision in the back of the neck, out of the animal's reach (16,33,40,68). Rats received buprenorphine (0.05 mg/kg sc) starting at the time of surgery and then every 8 -12 h postoperatively for a total of four doses.…”