Tier 4 — mechanistic

Fisetin Induces Nrf2-Mediated HO-1 Expression Through PKC-δ and p38 in Human Umbilical Vein Endothelial Cells

Lee SE, Jeong SI, Yang H, Park CS, Jin YH, Park YS
Journal of Cellular Biochemistry 2011 Volume 112, issue 9, pages 2352-2360

Bibliography

PubMed
PMID 21520244
DOI
10.1002/jcb.23158
Funding
National Research Foundation of Korea (NRF) grant funded by the Korean Government, grant no. 2010-0005872.
Competing interests
Not explicitly stated in the published article; no competing-interests declaration was identified in the extracted text.

Study snapshot

DesignIn vitro mechanistic study combining siRNA knockdown, pharmacological inhibitors, ARE-luciferase reporter assays, immunofluorescence, HO enzyme activity assay, and an H2O2-induced cytotoxicity rescue experiment.
ModelPrimary human umbilical vein endothelial cells (HUVECs).
SampleNot explicitly reported as a numeric N; experiments described as representative of replicate assays typical for this cell-biology methodology.
InterventionFisetin 5-25 µM for 1-24 hours; PKC-δ inhibitor rottlerin and p38 inhibitor SB203580; PKC-δ, p38 and Nrf2 siRNA knockdown; H2O2-induced cell death with or without the HO-1 inhibitor ZnPP.
DurationTime-course experiments from 1 to 24 hours of fisetin exposure.
EndpointsHeme oxygenase-1 (HO-1) protein, mRNA and enzyme activity; Nrf2 nuclear translocation (western blot, immunofluorescence); Antioxidant response element (ARE)-luciferase reporter activity; PKC-δ and p38 MAPK activation; Protection against H2O2-induced HUVEC cell death

What the study showed, in plain terms

This South Korean lab study looked at how fisetin protects the cells lining our blood vessels (endothelial cells) from oxidative stress, using human umbilical vein endothelial cells (HUVECs) as the model — a standard, widely used cell type for studying blood vessel biology.

Fisetin switched on a well-known cellular antioxidant defence pathway: it activated two signalling enzymes (PKC-δ and p38), which in turn caused the master antioxidant regulator Nrf2 to move into the cell nucleus and switch on a protective gene called heme oxygenase-1 (HO-1). Blocking either PKC-δ, p38, or Nrf2 stopped fisetin from turning on HO-1, confirming this specific signalling chain.

The practical payoff was shown directly: pre-treating the endothelial cells with fisetin protected them from dying when exposed to hydrogen peroxide (a classic oxidative-stress trigger), and this protection disappeared when the researchers blocked HO-1 with a chemical inhibitor (ZnPP) — solid evidence that HO-1 induction is the actual mechanism behind fisetin's protective effect here.

This fits fisetin's broader antioxidant reputation seen elsewhere in this Data Center, and is specifically relevant to cardiovascular and endothelial health, since HO-1 induction in blood vessel cells is considered protective against the oxidative damage involved in atherosclerosis and vascular ageing.

Key findings

  • Fisetin induced HO-1 protein, mRNA and enzyme activity in HUVECs in a concentration- and time-dependent manner (5-25 µM, 1-24 hours).
  • Pharmacological inhibition or siRNA knockdown of PKC-δ or p38 MAPK abolished fisetin-induced HO-1 expression, identifying both kinases as required upstream signals.
  • Fisetin caused Nrf2 nuclear translocation (confirmed by nuclear-fraction western blot and immunofluorescence), and Nrf2 siRNA knockdown abolished fisetin-induced HO-1 induction.
  • Fisetin dose-dependently activated an antioxidant response element (ARE)-luciferase reporter, consistent with direct transcriptional activation of the Nrf2/ARE pathway.
  • Fisetin pretreatment protected HUVECs from hydrogen peroxide-induced cell death, and this protection was reversed by the HO-1 inhibitor ZnPP, confirming HO-1 as the causal protective mechanism.
  • The overall signalling chain identified is: fisetin → PKC-δ and p38 activation → Nrf2 nuclear translocation → ARE activation → HO-1 upregulation → cytoprotection against oxidative stress.

What this study can and cannot tell us

This is a single-cell-type in vitro study using primary HUVECs; there is no animal model or human vascular data to confirm this mechanism translates to protection against oxidative vascular damage in vivo.

The fisetin concentrations used (5-25 µM) are broadly consistent with other in vitro fisetin work catalogued here, but still exceed typical plasma concentrations achievable through oral fisetin supplementation given its poor bioavailability.

No formal competing-interests or funding-disclosure statement beyond the single Korean NRF grant number was identified in the extracted text of this 2011 paper; older Journal of Cellular Biochemistry articles from this era did not always include the standardised disclosure sections used in more recent publications.

Editorial review

Reviewed by the Biohack Blueprint research team

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Dr. Khaled Mahmoud, MBBChCritical Care Medicine, Longevity Science & Editorial Direction Dr. Amr Yasser, PhDCardiometabolic, Musculoskeletal, Gut & Bioavailability Dr. Abdulla Mostafa, PhDCellular Senescence, Neurological, Mitochondrial & Brain-Ageing Biology