Punicalagin Induces Nrf2/HO-1 Expression via Upregulation of PI3K/AKT Pathway and Inhibits LPS-Induced Oxidative Stress in RAW264.7 Macrophages

Abstract

Reactive oxygen species (ROS) and oxidative stress are thought to play a central role in potentiating macrophage activation, causing excessive inflammation, tissue damage, and sepsis. Recently, we have shown that punicalagin (PUN) exhibits anti-inflammatory activity in LPS-stimulated macrophages. However, the potential antioxidant effects of PUN in macrophages remain unclear. Revealing these effects will help understand the mechanism underlying its ability to inhibit excessive macrophage activation. Hemeoxygenase-1 (HO-1) exhibits antioxidant activity in macrophages. Therefore, we hypothesized that HO-1 is a potential target of PUN and tried to reveal its antioxidant mechanism. Here, PUN treatment increased HO-1 expression together with its upstream mediator nuclear factor-erythroid 2 p45-related factor 2 (Nrf2). However, specific inhibition of Nrf2 by brusatol (a specific Nrf2 inhibitor) dramatically blocked PUN-induced HO-1 expression. Previous research has demonstrated that the PI3K/Akt pathway plays a critical role in modulating Nrf2/HO-1 protein expression as an upstream signaling molecule. Here, LY294002, a specific PI3K/Akt inhibitor, suppressed PUN-induced HO-1 expression and led to ROS accumulation in macrophages. Furthermore, PUN inhibited LPS-induced oxidative stress in macrophages by reducing ROS and NO generation and increasing superoxide dismutase (SOD) 1 mRNA expression. These findings provide new perspectives for novel therapeutic approaches using antioxidant medicines and compounds against oxidative stress and excessive inflammatory diseases including tissue damage, sepsis, and endotoxemic shock.

Cytoprotective effect of chlorogenic acid against hydrogen peroxide-induced oxidative stress in MC3T3-E1 cells through PI3K/Akt-mediated Nrf2/HO-1 signaling pathway

“…Many investigations have confirmed that upregulation of HO-1 contributes to the cellular defense mechanism in response to oxidative insults [20, 34, 37]. The present study showed that CGA treatment significantly upregulated HO-1 protein expression in a dose- and time-dependent manner, indicating that CGA exhibited antioxidant activity by upregulation HO-1 expression.…”

Haem oxygenase‐1 up‐regulation by rosiglitazone via ROS‐dependent Nrf2‐antioxidant response elements axis or PPARγ attenuates LPS‐mediated lung inflammation

“…Accumulating evidence indicates that rosiglitazone exerts anti‐inflammatory effects through up‐regulation of HO‐1 in the pulmonary system (Liu et al ., ; Kronke et al ., ; Li et al ., ; Xu et al ., ), suggesting a possible therapeutic application for treatment of inflammatory diseases (Belvisi and Mitchell, ). In our previous study, we found that rosiglitazone suppressed LPS‐induced nuclear translocation of phosphorylated NF‐κB (p65) and expression of adhesion molecules through a PPARγ‐dependent, up‐regulation of HO‐1 (Cho et al ., ).…”

“…Indeed, c‐Src is an upstream component of proline‐rich tyrosine kinase 2 (Pyk2) phosphorylation stimulated by TZDs (Peng et al ., ; Dewar et al ., ), which is regulated by ROS (Ke et al ., ), leading to HO‐1 expression in various cell types (Han et al ., ; Chi et al ., ; Yang et al ., ). Activated Akt triggers nuclear factor erythroid‐2‐related factor (Nrf2)/HO‐1 expression which could protect against cellular injury and promote cell survival (Deng et al ., ; Xu et al ., ). However, whether rosiglitazone‐induced HO‐1 expression mediated through NOX/ROS, c‐Src, Pyk2, Akt and Nrf2 was still unknown in HPAEpiCs.…”

Punicalagin attenuates palmitate‐induced lipotoxicity in HepG2 cells by activating the Keap1‐Nrf2 antioxidant defense system

“…However, whether and how punicalagin protects hepatocyte from FFA‐induced lipotoxicity remains unclear. Since activation of Nrf2 pathway by punicalagin was only observed in RAW264.7 cells , the current work has been designed to explore the mediating effect of punicalagin on Nrf2 pathway in HepG2 cells and potential protective effect on palmitate‐induced hepatoxicity.…”