The Therapeutic Roles of Recombinant Hsp90α on Cornea Epithelial Injury

Effects of hypoxia in the diabetic corneal stroma microenvironment

Corneal dysfunctions associated with Diabetes Mellitus (DM), termed diabetic keratopathy (DK), can cause impaired vision and/or blindness. Hypoxia affects both Type 1 (T1DM) and Type 2 (T2DM) surprisingly, the role of hypoxia in DK is unexplored. The aim of this study was to examine the impact of hypoxia in vitro on primary human corneal stromal cells derived from Healthy (HCFs), and diabetic (T1DMs and T2DMs) subjects, by exposing them to normoxic (21% O2) or hypoxic (2% O2) conditions through 2D and 3D in vitro models. Our data revealed that hypoxia affected T2DMs by slowing their wound healing capacity, leading to significant alterations in oxidative stress-related markers, mitochondrial health, cellular homeostasis, and endoplasmic reticulum health (ER) along with fibrotic development. In T1DMs, hypoxia significantly modulated markers related to membrane permeabilization, oxidative stress via apoptotic marker (BAX), and protein degradation. Hypoxic environment induced oxidative stress (NOQ1 mediated reduction of superoxide in T1DMs and Nrf2 mediated oxidative stress in T2DMs), modulation in mitochondrial health (Heat shock protein 27 (HSP27), and dysregulation of cellular homeostasis (HSP90) in both T1DMs and T2DMs. This data underscores the significant impact of hypoxia on the diabetic cornea. Further studies are warranted to delineate the complex interactions.

Kaempferol exerts antioxidant effects in age-related diminished ovarian reserve by regulating the HSP90/NRF2 pathway

Kaempferol is the active ingredient of Er-Xian decoction (EXD), a traditional Chinese medicine formula used clinically to treat ovarian dysfunction, but the mechanism of kaempferol relieving age-related diminished ovarian reserve (AR-DOR) is still unclear. In this study, 36 volunteers and 78 DOR patients (37 patients with EXD treatment) were enrolled in the clinical research. Meanwhile, 32-week-old female mice were used to establish the AR-DOR model, and these model mice were intragastrically administered with 100 mg/kg kaempferol in the presence or absence of 200 mg/kg geranylgeranylacetone (GGA) or 1 mg/kg geldanamycin (GDA). The effects of kaempferol on serum hormone levels and oxidative stress-related indexes were detected by enzyme-linked immunosorbent assay. Antral follicle count (AFC) was determined by hematoxylin-eosin staining. The protein levels of HSP90 and nuclear factor erythroid 2-related factor 2 (NRF2) were assayed by Western blot. This study displayed that the serum anti-Mullerian hormone (AMH) level in DOR patients with EXD treatment was higher than that in DOR patients without EXD treatment. Kaempferol treatment reversed the low levels of AMH, estradiol (E2), AFC, superoxide dismutase (SOD), and catalase (CAT), as well as the high levels of follicle-stimulating hormone (FSH), reactive oxygen species (ROS), and malonaldehyde (MDA). The results showed that HSP90 was predicted to have high affinity with kaempferol, and its expression was inhibited by kaempferol, while the expression of NRF2, the target of HSP90, was up-regulated by kaempferol. However, the above effects of kaempferol were reversed by GGA. On the contrary, GDA enhanced the therapeutic effects of kaempferol on AR-DOR mice. Moreover, the treatment of kaempferol resulted in a reduction in the phosphorylation level of heat shock factor 1 (HSF1), the transcription factor associated with HSP90, and an increase in the phosphorylation level of Src, a client protein of HSP90. In summary, kaempferol exerts an antioxidant effect on AR-DOR by inhibiting HSP90 expression to up-regulate NRF2 expression. This study provides a theoretical basis for the clinical application of kaempferol in AR-DOR.

Extracellular HSP90 promotes differentiation of lens epithelial cells to fiber cells by activating LRP1-YAP-PROX1 axis

Capsular residual lens epithelial cells (CRLEC) undergo differentiation to fiber cells for lens regeneration or tansdifferentiation to myofibroblasts leading to posterior capsular opacification (PCO) after cataract surgery. The underlying regulatory mechanism remains unclear. Using human lens epithelial cell lines and the ex vivo cultured rat lens capsular bag model, we found that the lens epithelial cells secrete HSP90α extracellularly (eHSP90) through an autophagy-associated pathway. Administration of recombinant GST-HSP90α protein or its M-domain induces the elongation of rat CRLEC cells with concomitant upregulation of the crucial fiber cell transcriptional factor PROX1and its downstream targets, β- and γ-crystallins and structure proteins. This regulation is abolished by PROX1 siRNA. GST-HSP90α upregulates PROX1 by binding to LRP1 and activating LRP1-AKT mediated YAP degradation. The upregulation of GST-HSP90α on PROX1 expression and CRLEC cell elongation is inhibited by LRP1 and AKT inhibitors, but activated by YAP-1 inhibitor (VP). These data demonstrated that the capsular residue epithelial cells upregulate and secrete eHSP90α, which in turn drive the differentiation of lens epithelial cell to fiber cells. The recombinant HSP90α protein is a potential novel differentiation regulator during lens regeneration.