Chlorogenic Acid Increases Basal Tone with No Effect on Relaxation of Rat Ileal Smooth Muscles by Mechanisms Independent of PKG Mediated Effects on Myosin Light Chain Phosphorylation
The FASEB Journal
Chlorogenic acid (CGA) is a dietary polyphenolic compound commonly present in coffee, fruits and vegetables. The pharmacological properties of CGA include antioxidant, antibacterial, anti-inflammatory, and antithrombotic effects. Previous experimental studies have shown that CGA induces nitric oxide-sGC-PKG pathway to cause relaxation of the vascular smooth muscles. But the effects of CGA on ileal smooth muscles are still unknown. The present study is designed to test the effect of CGA on PKG mediated relaxation of rat ileal smooth muscle.
Effects of CGA on basal tension and maximum contractile tension induced by physiological salt solution (PSS) containing 140 mM potassium in isolated rat ileal rings (3mm) were determined using tissue bath apparatus. CGA effects on myosin light chain phosphorylation at maximum contractile tension were also measured by freezing the ileal rings and extracting the protein and running Western blots. The role of PKG in regulating smooth muscle relaxation is tested by incubating ileal rings with specific PKG inhibitor Rp-8-Br-cGMPS and measuring the basal tension, maximum contractile tension and myosin light chain phosphorylation as described above.
The results show that basal tension increases from 0.27±0.1 (control group) to 0.91±0.3 and 0.87±0.2 (mV) when treated with CGA (10μM) and PKG inhibitor (4μM) respectively. The peak contractile tension in response depolarization by 140 mM K+ PSS changes from 100% (control group) to 101±12.2 % and 117±17.2 % when treated with CGA and PKG inhibitor respectively. The results from Western blots show that myosin light chain phosphorylation didn’t change significantly between CGA (36.3±0.8 %) and PKG inhibitor (35.8±0.5 %) treatments.
These results suggest that CGA is involved in increasing the basal tone of ileal smooth muscles when compared with the control group. In addition, CGA did not have any effect on the peak contractile tension and myosin light chain phosphorylation, suggesting that it may not be involved in ileal smooth muscle relaxation. However, PKG inhibitor in presence of CGA did increase basal and maximum contractile tension without any corresponding changes in myosin light chain phosphorylation indicating that other mechanisms that doesn’t include PKG mediated effects on myosin light chain phosphorylation may be important in regulating basal tone of ileal smooth muscle by CGA.
Chlorogenic acid, basal tone, rat ileal smooth muscles, PKG, myosin light chain phosphorylation
Berman, Sarah; Huston, Jamie; Lail, Austin; Piquette, Nicole; and Injeti, Elisha R., "Chlorogenic Acid Increases Basal Tone with No Effect on Relaxation of Rat Ileal Smooth Muscles by Mechanisms Independent of PKG Mediated Effects on Myosin Light Chain Phosphorylation" (2019). Pharmaceutical Sciences Faculty Publications. 177.
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