Ming-Mu-Di-Huang-Pill Activates SQSTM1 via AMPK-Mediated Autophagic KEAP1 Degradation and Protects RPE Cells from Oxidative Damage

Abstract

Oxidative stress and diminished autophagy in the retinal pigment epithelium (RPE) play crucial roles in the pathogenesis of age-related macular degeneration (AMD). Enhancing autophagy has recently been identified as an important strategy to protect RPE cells from oxidative damage. Ming-Mu-Di-Huang-Pill (MMDH pill) is a traditional herbal medicine used to treat AMD, and its molecular mechanism is not well understood. The aim of the present study was to investigate whether the MMDH pill relieved acute oxidative damage by activating autophagy in an in vitro and in vivo model of sodium iodate (NaIO3). The results showed that NaIO3 induced cell death and inhibited proliferation. The MMDH pill increased cell viability, restored the activities of antioxidant enzymes, and reduced reactive oxygen species (ROS) fluorescence intensity. The MMDH pill mediated Kelch-like ECH-associated protein 1 (Keap1) degradation and decreased oxidative damage, which was blocked in autophagy inhibitor (chloroquine) or sequestosome-1 (SQSTM1) siRNA-treated RPE cells. Furthermore, we indicated that the MMDH pill could promote adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and autophagy adaptor-SQSTM1 expression, which could stimulate autophagic degradation of Keap1. In addition, the MMDH pill increased nuclear factor (erythroid-derived 2)-like 2 (Nrf2) nuclear translocation in a SQSTM1-dependent manner and induced the expression of the downstream antioxidant factors heme oxygenase-1 (HO-1) and nicotinamide adenine dinucleotide phosphate quinone dehydrogenase 1 (NQO1). In conclusion, MMDH pill plays a protective role in relieving NaIO3-induced oxidative stress by activating the AMPK/SQSTM1/Keap1 pathway. The MMDH pill may be useful to treat AMD by maintaining redox homeostasis and autophagy.

Role of AMPK-regulated autophagy in retinal pigment epithelial cell homeostasis: A review

“…In AMD, RPE cannot downregulate, indicating dysfunctional autophagy in AMD RPE. [45] CHEN et al [56] showed that Ming-Mu-Di-Huang-Pill (MMDH) promotes AMPK phosphorylation and p62 expression, and LC3-II protein expression, suggesting that MMDH slices enhance autophagic flux, and that p62 stimulates autophagic degradation of KEAP1, releases nuclear factor erythroid 2-related factor 2 (NRF2), and induces Heme oxygenase-1 and NAD (P)H: quinone oxidoreductase 1 expression, preventing oxidative damage in RPE cells, which contributes to the treatment of AMD. Yu et al [57] found that phosphorylation of p62 by AMPK in the RPE promotes the binding of p62 to KEAP1 and leads to the release of NRF2 from the NRF2-KEAP1 complex, which promotes GSH, prevents intracellular ROS production, and reduces oxidative stress, which may be associated with autophagy.…”

Baicalin Attenuates H2O2-Induced Oxidative Stress by Regulating the AMPK/Nrf2 Signaling Pathway in IPEC-J2 Cells

“…Nrf2 is a redox-sensitive transcription factor that inhibits oxidative stress production by regulating the expression of antioxidant enzyme genes, and AMPK is an important energy metabolism signal pathway gene that affects mitochondrial function and autophagy. AMPK and Nrf2 have an important regulatory effect on oxidative stress and synergize with other transcription factors to produce an antioxidant and antiinflammatory effect [9,10]. In addition, activating AMPK induced mitochondrial autophagy, which reduced ROS overproduction, intestinal epithelium barrier injury, and mitochondrial dysfunction [11].…”

Poria acid alleviates oxidative damage in mice with dry age-related macular degeneration by activating the Nrf2/HO-1 signaling pathway

“…Nrf2 can be found in the cytoplasm as a dimer formed with Kelch-like ECH-associated protein 1 (Keap1), however, when subjected to stimuli such as oxidative stress, it will dissociate from Keap1 and transferred to the nucleus where it binds to ARE, and regulate the expression of ARE-mediated phase II detoxi cation and antioxidant enzymes, including heme oxygenase-1 (HO-1), glutamate-Cysteine ligase (GCL) and NAD(P)H: quinone oxidoreductase (NQO1) (9), among which, HO-1 showed to be an important antioxidant enzyme that reduces cell damage (10). The upregulation of Nrf2 protects retinal cells from oxidative damage and rescues the function of the retina (11)(12)(13) Recent studies have demonstrated, the Nrf2/HO-1 signaling pathway can be activated by abundant bioactive compounds from natural products to regulate the traumatic and stressed status of the retina (14).…”