Heme Modulates Bladder Contractility Through the HO-CO-sGC-cGMP Pathway: Insights into Sickle Cell Disease-Associated...

Area of Science:

• Physiology
• Biochemistry
• Pharmacology

Background:

• Intravascular hemolysis in sickle cell disease elevates plasma heme.
• Heme's role in bladder function is unknown, despite its physiological importance and potential toxicity.
• The heme oxygenase (HO)-carbon monoxide (CO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) pathway influences smooth muscle tone.

Purpose of the Study:

• To investigate if heme regulates detrusor smooth muscle contractility via the HO-CO-sGC-cGMP pathway.
• To determine the direct effects of heme on bladder function.

Main Methods:

• Functional analysis of detrusor smooth muscle strips from C57BL/6 mice using myography.
• Exposure to heme with and without HO (1J) and sGC (ODQ) inhibitors.
• Measurement of contractile responses to carbachol, KCl, and electrical field stimulation (EFS).
• Biochemical assays to quantify cGMP levels in detrusor tissue.

Main Results:

• Heme induced concentration-dependent relaxation of detrusor smooth muscle.
• HO and sGC inhibitors attenuated heme-induced relaxation and decreased maximal contractile responses.
• Heme increased detrusor cGMP levels, an effect blocked by inhibitors.
• Heme reduced maximal contractile responses to various stimuli, an effect abolished by inhibitors.

Conclusions:

• Heme modulates bladder contractility by activating the HO-CO-sGC-cGMP pathway, leading to detrusor relaxation.
• Excess heme in hemolytic disorders may cause detrusor hypocontractility and voiding dysfunction.
• The HO-CO-sGC-cGMP pathway represents a potential therapeutic target for heme-related bladder dysfunction.