Nitric oxide increases adrenomedullin receptor function in rat mesangial cells

Area of Science:

• Nephrology
• Molecular Biology
• Cell Biology

Background:

• Adrenomedullin (ADM) exhibits antiproliferative effects on rat mesangial cells, suggesting potential renoprotective properties.
• Nitric oxide (NO) has complex roles, capable of both cytoprotective and cytotoxic actions in cellular systems.

Purpose of the Study:

• To investigate whether nitric oxide (NO) stimulates the adrenomedullin (ADM) system in rat mesangial cells.
• To elucidate the signaling pathways involved in the interaction between NO and ADM.

Main Methods:

• Rat mesangial cells were treated with NO donors (GSNO, SNAP), a guanylate cyclase inhibitor (ODQ), and a cGMP analog (8-bromo-cGMP).
• Measurements included ADM radioligand binding, ADM-induced intracellular cAMP accumulation, and ADM receptor gene expression via TaqMan real-time PCR.

Main Results:

• NO donors (GSNO, SNAP) significantly increased maximal ADM binding to its receptor.
• NO donors and 8-bromo-cGMP altered the EC50 for ADM binding, indicating enhanced signal transduction.
• ADM receptor gene expression was downregulated by NO donors and 8-bromo-cGMP, but not by 8-bromo-cAMP.

Conclusions:

• Nitric oxide (NO) enhances ADM signal transduction via a cGMP-dependent pathway, partly by increasing ADM receptor availability.
• A feedback mechanism at the mRNA level counteracts the effects of NO on ADM receptor gene expression.
• This interplay between NO and ADM signaling may contribute to the cytoprotective effects of NO on mesangial cells.