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Amorfrutin B Compromises Hypoxia/Ischemia-induced Activation of Human Microglia in a PPARγ-dependent Manner: Effects
Karolina Przepiórska-Drońska1, Agnieszka Wnuk1, Bernadeta Angelika Pietrzak-Wawrzyńska1
1Maj Institute of Pharmacology, Polish Academy of Sciences, Department of Pharmacology, Laboratory of Neuropharmacology and Epigenetics, Smetna Street 12, 31-343, Krakow, Poland.
Abstract:
Amorfrutin B is a selective PPARγ modulator that we demonstrated to be a promising neuroprotective compound in cellular models of stroke and perinatal asphyxia. Although neuronal mechanisms of amorfrutin B-evoked neuroprotection have been identified, none of them reflects the actions of the compound on microglia, which play a pivotal role in brain response to hypoxia/ischemia. Here, we provide evidence for amorfrutin B-induced effects on human microglia subjected to hypoxia/ischemia; the compound counteracts inflammation, and influences mitochondrial status and proliferation potential in a PPARγ-dependent manner. Post-treatment with amorfrutin B decreased the IBA1 fluorescence intensity, reduced caspase-1 activity, and downregulated IL1B/IL-1β and TNFA but not IL10/IL-10 expression, which was upregulated. Amorfrutin B also stimulated PPARγ signaling, as evidenced by increased mRNA and/or protein levels of PPARγ and PGC1α. In addition, amorfrutin B reversed the hypoxia/ischemia-evoked effects on mitochondria-related parameters, such as mitochondrial membrane potential, BCL2/BCL2 expression and metabolic activity, which were correlated with diminished proliferation potential of microglia. Interestingly, the inhibitory effect of amorfrutin B on the proliferation potential and mitochondrial function of microglia is opposite to the stimulatory effect of amorfrutin B on mouse neuronal survival, as evidenced by increased neuronal viability and reduced neurodegeneration. In summary, this study showed for the first time that amorfrutin B compromises hypoxia/ischemia-induced activation of human microglia in a PPARγ-dependent manner, which involves inhibiting inflammation, normalizing mitochondrial status, and controlling proliferation potential. These data extend the protective potential of amorfrutin B in the pharmacotherapy of hypoxic/ischemic brain injury, targeting not only neurons but also activated microglia.
Insights
Amorfrutin B protects the brain from hypoxic/ischemic injury by modulating microglia. This compound reduces inflammation and normalizes mitochondrial function in microglia, offering new therapeutic potential for brain damage.
Area of Science:
- Neuroscience
- Pharmacology
- Cell Biology
Background:
- Microglia play a critical role in the brain's response to hypoxia/ischemia.
- Previous research identified amorfrutin B as a neuroprotective agent but did not elucidate its effects on microglia.
- Understanding amorfrutin B's impact on microglia is crucial for its therapeutic application in hypoxic/ischemic brain injury.
Purpose of the Study:
- To investigate the effects of amorfrutin B on human microglia under hypoxia/ischemia.
- To determine if these effects are dependent on Peroxisome proliferator-activated receptor gamma (PPARγ) signaling.
- To evaluate amorfrutin B's influence on microglial inflammation, mitochondrial function, and proliferation.
Main Methods:
- Human microglia were subjected to hypoxia/ischemia and treated with amorfrutin B.
- Assessed microglial activation markers (IBA1), inflammatory cytokines (IL1B, TNFA, IL10), and caspase-1 activity.
- Measured PPARγ signaling, mitochondrial parameters (membrane potential, BCL2 expression, metabolic activity), and cell proliferation.
Main Results:
- Amorfrutin B counteracted inflammation by reducing IBA1 intensity, caspase-1 activity, IL1B, and TNFA, while upregulating IL10.
- The compound stimulated PPARγ signaling, increasing PPARγ and PGC1α levels.
- Amorfrutin B normalized mitochondrial function and reduced microglial proliferation, contrasting with its pro-neuronal survival effects.
Conclusions:
- Amorfrutin B inhibits hypoxia/ischemia-induced microglial activation in a PPARγ-dependent manner.
- The compound's mechanisms involve reducing inflammation, normalizing mitochondrial status, and controlling proliferation.
- These findings highlight amorfrutin B's potential as a therapeutic agent for hypoxic/ischemic brain injury, targeting both neurons and microglia.
