Uric acid enhances PKC-dependent eNOS phosphorylation and mediates cellular ER stress: A mechanism for uric acid-induced endothelial dysfunction.
Level 5 - mechanism / opinion, no new human data
In vitro bench research on cultured human cells
PubMed 26935704 · doi:10.3892/ijmm.2016.2491
What was done
Human umbilical vein endothelial cells (HUVECs) were incubated with uric acid (6, 9, or 12 mg/dl) for 6 to 48 hours with or without the ROS scavenger PEG-SOD, the ER stress inhibitor 4-PBA, or the PKC inhibitor polymyxin B. Investigators evaluated nitric oxide production, eNOS activity, intracellular ROS, ER stress levels, intracellular calcium levels, calmodulin expression, eNOS phosphorylation (Ser1177 and Thr495), and the eNOS-calmodulin interaction using fluorescence microscopy and western blot analysis. Apoptosis was measured using annexin V staining.
What was found
The abstract reports that uric acid increased HUVEC apoptosis and decreased eNOS activity and nitric oxide production in a dose- and time-dependent manner, but provides no specific numerical values. Intracellular ROS increased after 3 hours, and ER stress markers increased after 6 hours. Uric acid did not change intracellular calcium, calmodulin, total eNOS levels, or eNOS Ser1177 phosphorylation, but it enhanced PKC-dependent eNOS Thr495 phosphorylation and reduced the interaction between eNOS and calmodulin. Depleting ROS, inhibiting ER stress, and reducing PKC activity each prevented the uric acid-induced reduction in eNOS activity and nitric oxide release, as well as the increase in apoptosis.
Why it matters
This study outlines an intracellular pathway linking elevated uric acid to reduced nitric oxide bioavailability and endothelial cell death. It provides a plausible cellular mechanism for how hyperuricemia might directly promote endothelial dysfunction in cardiovascular disease.
Limits
The abstract reports no numerical effect sizes, dispersion measures, or sample sizes/replicate counts. As an in vitro study performed exclusively on cultured umbilical vein endothelial cells, it does not assess whole-vessel physiology, animal models, or clinical hyperuricemia in humans.
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