Garlic attenuates nitric oxide production in rat cardiac myocytes through inhibition of inducible nitric oxide synthase and the arginine transporter CAT-2 (cationic amino acid transporter-2)

2002 ◽  
Vol 102 (5) ◽  
pp. 487-493 ◽  
Author(s):  
Idit F. SCHWARTZ ◽  
Rami HERSHKOVITZ ◽  
Adrian IAINA ◽  
Ehud GNESSIN ◽  
Yoram WOLLMAN ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Antioxidant Activity ◽  
Steady State ◽  
Amino Acid ◽  
Cardiac Myocytes ◽  
Inos Mrna ◽  
Mrna Levels ◽  
Cationic Amino Acid Transporter ◽  
Cationic Amino Acid ◽  
Nitrite Production

It is now accepted that allicin, the main biologically active compound in garlic, exhibits antioxidant activity. The present study was designed to test the hypothesis that the antioxidant activity of garlic can be partially attributed to the inhibition of nitric oxide (NO) production by cytokine-induced NO synthase (iNOS). Cardiac myocytes cultured from neonatal Wistar rats were stimulated by lipopolysaccharide (LPS) and incubated for 24h with various concentrations of allicin. This resulted in marked inhibition of nitrite production. Interestingly, a low concentration of allicin (10μM) was significantly more potent in abrogating the effect of LPS on nitrite production than a higher concentration (40μM). Allicin decreased steady-state iNOS mRNA levels, and this effect was maximal when a lower concentration was used (10μM compared with 40μM). In order to explore additional effects of allicin on NO generation that might counteract the effect on iNOS, we assessed the effects of higher allicin concentrations on arginine transport. Allicin inhibited the uptake of 1mM extracellular arginine in a concentration-dependent manner. The expression of the two arginine transporters that are expressed in cardiac myocytes [CAT-1 (cationic amino acid transporter-1) and CAT-2] was studied using reverse transcription-PCR. A concentration of 200μM allicin abolished the expression of CAT-2 mRNA, 100μM significantly attenuated it, whereas 50μM had no effect. Allicin had no effect on steady-state CAT-1 mRNA levels. Our results suggest that allicin inhibits iNOS activity through two different mechanisms: at lower concentrations it decreases iNOS mRNA levels, whereas at higher concentrations it inhibits arginine transport through down-regulation of CAT-2 mRNA.

scholarly journals Nitric oxide can acutely modulate its biosynthesis through a negative feedback mechanism on l-arginine transport in cardiac myocytes

2010 ◽  
Vol 299 (2) ◽  
pp. C230-C239 ◽  
Author(s):  
Jiaguo Zhou ◽  
David D. Kim ◽  
R. Daniel Peluffo
Keyword(s):  
Nitric Oxide ◽  
Amino Acid ◽  
Cardiac Myocytes ◽  
Amino Acid Transporters ◽  
No Production ◽  
Cardiac Muscle Cells ◽  
No Donor ◽  
Rat Cardiomyocytes ◽  
Cationic Amino Acid ◽  
Intervention Point

Nitric oxide (NO) plays a central role as a cellular signaling molecule in health and disease. In the heart, NO decreases the rate of spontaneous beating and the velocity and extent of shortening and accelerates the velocity of relengthening. Since the cationic amino acid l-arginine (l-Arg) is the substrate for NO production by NO synthases (NOS), we tested whether the transporters that mediate l-Arg import in cardiac muscle cells represent an intervention point in the regulation of NO synthesis. Electrical currents activated by l-Arg with low apparent affinity in whole cell voltage-clamped rat cardiomyocytes were found to be rapidly and reversibly inhibited by NO donors. Radiotracer uptake studies performed on cardiac sarcolemmal vesicles revealed the presence of high-affinity/low-capacity and low-affinity/high-capacity components of cationic amino acid transport that were inhibited by the NO donor S-nitroso- N-acetyl-dl-penicillamine. NO inhibited uptake in a noncompetitive manner with Ki values of 275 and 827 nM for the high- and low-affinity component, respectively. Fluorescence spectroscopy experiments showed that millimolar concentrations of l-Arg initially promoted and then inhibited the release of endogenous NO in cardiomyocytes. Likewise, l-Arg currents measured in cardiac myocytes voltage clamped in the presence of 460 nM free intracellular Ca2+, a condition in which a Ca-CaM complex should activate endogenous NO production, showed fast activation followed by inhibition of l-Arg transport. The NOS inhibitor N-nitro-l-arginine methyl ester, but not blockers of downstream reactions, specifically removed this inhibitory component. These results demonstrate that NO acutely regulates its own biosynthesis by modulating the availability of l-Arg via cationic amino acid transporters.

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