Nitric oxide-generating system as an autocrine mechanism in human polymorphonuclear leucocytes

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Endothelin-1 (ET-1) increases intracellular calcium in polymorphonuclear leukocytes (PMN).
• L-arginine can inhibit ET-1's effect on PMN calcium levels.
• The interaction mechanisms between ET-1 and L-arginine in human PMN require further elucidation.

Purpose of the Study:

• To investigate the interplay between ET-1 and L-arginine in human PMN.
• To elucidate the signaling pathways involved in ET-1 and L-arginine interactions.
• To characterize the L-arginine transport system in PMN.

Main Methods:

• Measurement of L-arginine metabolism to L-citrulline.
• Quantification of cyclic GMP (cGMP) formation.
• Assessment of nitric oxide (NO) involvement using NG-monomethyl-L-arginine.
• Characterization of L-arginine transport via Na(+)-dependent and -independent components.
• Analysis of L-arginine transport regulation by NO/cGMP.

Main Results:

• ET-1 and fMLP stimulate L-arginine metabolism and cGMP production in human PMN.
• ET-1-induced cGMP formation is NO-dependent and requires L-arginine availability.
• Human PMN possess a distinct L-arginine transport system.
• This transport system is feedback-regulated by NO/cGMP under ET-1 stimulation.
• The L-arginine transport system is independent of the gamma-glutamyl cycle.

Conclusions:

• L-arginine/NO/cGMP-dependent pathways are involved in ET-1 and fMLP signaling in human PMN.
• L-arginine availability and transport are critical for PMN activation.
• These mechanisms may play a role in regulating PMN function in disease states.