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Substance P induced changes in CD74 and CD44 in the rat bladder
Katherine L Meyer-Siegler1, Pedro L Vera
1Research and Development Service, Bay Pines Veterans Affairs Medical Center, Bay Pines, Florida 33744, USA. Katherine.Siegler@med.va.gov
Purpose:
Substance P (SP) induces rat bladder inflammation along with release of the proinflammatory cytokine, macrophage migration inhibitory factor (MIF). To describe the mechanism of MIF action we examined changes in the amount of CD74 (membrane receptor for MIF), CD44 and phospho-(p-ERK)1/2 in the bladder.
Materials And Methods:
In anesthetized rats the bladder was isolated by cutting the ureters and urine was replaced by saline as intraluminal fluid (ILF). One hour after subcutaneous SP (40 mug/kg) or saline administration the ILF and bladder were collected. Bladder tissue was analyzed for CD74 and CD44 by immunohistochemistry. Western blot analysis determined the relative amounts of bladder tissue MIF, CD74, CD44 and p-ERK1/2. ILF immunoprecipitation followed by Western blot analysis was performed to identify an association of MIF with CD74 and/or CD44.
Results:
SP induced significant MIF release from the bladder and increased CD74 and CD44 bladder immunostaining. SP treatment increased the total amount of bladder CD74 protein and mRNA, intracellular domain CD44, p-ERK1/2 and soluble CD44 in the ILF. Finally, MIF was found to be associated with soluble CD44 in the ILF.
Conclusions:
CD74 is present in the rat urothelium. SP increases CD74 and intracellular domain CD44 in the bladder, while stimulating the release of soluble CD44 and MIF into the ILF. MIF interacts with soluble CD44 in the ILF and it is available to bind with CD74 in the bladder to exert proinflammatory effects. Therefore, a mechanistic model is emerging to explain the proinflammatory effects of MIF in this acute model of bladder inflammation. Possible clinical implications are discussed.
Insights
Substance P (SP) triggers bladder inflammation and macrophage migration inhibitory factor (MIF) release. MIF interacts with soluble CD44 and binds to CD74, driving proinflammatory effects in the bladder.
Area of Science:
- Urology
- Immunology
- Cell Biology
Background:
- Substance P (SP) is known to induce bladder inflammation.
- Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine released during SP-induced inflammation.
- The precise mechanism of MIF's action in bladder inflammation requires further elucidation.
Purpose of the Study:
- To investigate the mechanism of MIF action in SP-induced rat bladder inflammation.
- To examine changes in CD74, CD44, and phospho-ERK1/2 levels in the bladder.
- To determine the association between MIF, CD74, and CD44.
Main Methods:
- Rats were treated with SP or saline.
- Bladder tissue and intraluminal fluid (ILF) were collected.
- Immunohistochemistry and Western blot analysis were used to quantify MIF, CD74, CD44, and p-ERK1/2.
- ILF immunoprecipitation identified MIF-CD74/CD44 associations.
Main Results:
- SP induced significant MIF release and increased CD74 and CD44 expression in the bladder.
- SP treatment elevated bladder CD74 mRNA and protein, intracellular CD44, and p-ERK1/2.
- Soluble CD44 and MIF were detected in the ILF, with MIF associated with soluble CD44.
Conclusions:
- CD74 is present in the rat urothelium.
- SP upregulates CD74 and intracellular CD44, releasing soluble CD44 and MIF.
- MIF interacts with soluble CD44 and binds to CD74, mediating proinflammatory effects in bladder inflammation.
