Unfolded Protein Response Pathways Correlatively Modulate Endoplasmic Reticulum Stress Responses in Rat Retinal Müller Cells

Ultrasound biomicroscopy in the management of complex cataract and intraocular lens: A review

Ultrasound biomicroscopy (UBM) is an invaluable investigation for imaging anterior segment structures. Although it is operator-dependent and time consuming, unlike optical-based imaging techniques, it is able to image structures posterior to the iris, such as the zonules, ciliary body and part of the pars plana. It is especially useful in advanced cataracts, traumatic cataracts, subluxed lenses, posterior polar cataracts, and congenital and developmental anomalies affecting the anterior segment. It provides diagnostic information in eyes with complex cataracts or intraocular lens (IOL)-related pathology, and aids in surgical planning in order to minimise complications. In this review, we describe the UBM features of various lenticular pathologies and demonstrate its application in the diagnosis and surgical management of lens and IOL-related pathologies.

Polyethylene microplastics induced inflammation via the miR-21/IRAK4/NF-κB axis resulting to endoplasmic reticulum stress and apoptosis in muscle of carp

As a widespread environmental pollutant, microplastics pose a great threat to the tissues and organs of aquatic animals. The carp's muscles are necessary for movement and survival. However, the mechanism of injury of polyethylene microplastics (PE-MPs) to carp muscle remains unclear. Therefore, in this study, PE-MPs with the diameter of 8 μm and the concentration of 1000 ng/L were used to feed carp for 21 days, and polyethylene microplastic treatment groups was established. The results showed that PE-MPs could cause structural abnormalities and disarrangement of muscle fibers, and aggravate oxidative stress in muscles. Exposure to PE-MPs reduced microRNA (miR-21) in muscle tissue, negatively regulated Interleukin-1 Receptor Associated Kinase 4 (IRAK4), activated Nuclear Factor Kappa-B (NF-κB) pathway, induced inflammation, and led to endoplasmic reticulum stress and apoptosis. The present study provides different targets for the prevention of muscle injury induced by polyethylene microplastics.

Mitochondria and Endoplasmic Reticulum Stress in Retinal Organoids from Patients with Vision Loss

Activating transcription factor 6 (ATF6), a key regulator of the unfolded protein response, plays a key role in endoplasmic reticulum function and protein homeostasis. Variants of ATF6 that abrogate transcriptional activity cause morphologic and molecular defects in cones, clinically manifesting as the human vision loss disease achromatopsia (ACHM). ATF6 is expressed in all retinal cells. However, the effect of disease-associated ATF6 variants on other retinal cell types remains unclear. Herein, this was investigated by analyzing bulk RNA-sequencing transcriptomes from retinal organoids generated from patients with ACHM, carrying homozygous loss-of-function ATF6 variants. Marked dysregulation in mitochondrial respiratory complex gene expression and disrupted mitochondrial morphology in ACHM retinal organoids were identified. This indicated that loss of ATF6 leads to previously unappreciated mitochondrial defects in the retina. Next, gene expression from control and ACHM retinal organoids were compared with transcriptome profiles of seven major retinal cell types generated from recent single-cell transcriptomic maps of nondiseased human retina. This indicated pronounced down-regulation of cone genes and up-regulation in Müller glia genes, with no significant effects on other retinal cells. Overall, the current analysis of ACHM patient retinal organoids identified new cellular and molecular phenotypes in addition to cone dysfunction: activation of Müller cells, increased endoplasmic reticulum stress, disrupted mitochondrial structure, and elevated respiratory chain activity gene expression.

Copper induced intestinal inflammation response through oxidative stress induced endoplasmic reticulum stress in Takifugu fasciatus

Copper (Cu) pollution in aquaculture water has seriously threatened the healthy and sustainable development of the aquaculture industry. Recently, many researchers have studied the toxic effects of Cu exposure on fish. However, the relationship between endoplasmic reticulum stress (ERS) and the inflammatory response, as well as its possible mechanisms, remain unclear. Particularly, information related to fish intestines must be expanded. Our study initially investigated the mechanisms underlying intestinal toxicity and inflammation resulting from Cu-induced ERS in vivo and in vitro in Takifugu fasciatus. In vivo study, T. fasciatus were treated with different concentrations (control, 20, and 100 µg/L) of Cu exposure for 28 days, causing intestinal oxidative stress, ERS, inflammatory responses, and histopathological and ultrastructural damage. Transcriptomic data further showed that Cu exposure caused ERS, as well as inflammatory responses, in the intestinal tracts of T. fasciatus. In vitro experiments on the intestinal cells of T. fasciatus showed that Cu exposure treatment (7.5 µg/mL) for 24 h induced ERS and increased mitochondrial numbers and inflammatory responses. In contrast, the addition of 4-phenylbutyric acid (4-PBA) alleviated ERS and inflammatory response in the Cu-exposed group. Furthermore, the reactive oxygen species (ROS) inhibitor, N-Acetyl-l-cysteine (NAC), effectively alleviated Cu-induced ERS. In conclusion, our in vivo and in vitro studies have confirmed that oxidative stress triggers the ERS pathway, which is involved in the intestinal inflammatory response. Our study provides new insights into the relationship among Cu-induced oxidative stress, ERS, and inflammatory responses in fish, as well as for the healthy culture of fish in aqueous environments.

Rhein protects retinal Müller cells from high glucose-induced injury via activating the AMPK/Sirt1/PGC-1α pathway

Oxidative stress, inflammation and apoptosis are important pathogenic factors of diabetic retinopathy (DR). In the current study, we aimed to evaluate the potential role of Rhein, a natural anthraquinone compound found in rhubarb, in high glucose (HG)-induced Müller cells (MIO-M1). Cell Counting Kit‑8 assay, TUNEL assay, Western blot analysis, Reverse transcription quantitative polymerase chain reaction (RT-qPCR), and ELISA were conducted to assess the effects of Rhein on Müller cells. Additionally, the EX-527, an Sirt1 inhibitor, was used to study whether the effects of Rhein, on HG-induced Müller cells were mediated by activation of the Sirt1 signaling pathway. Our data showed that Rhein improved cell viability of HG-induced Müller cells. Rhein reduced the ROS and MDA production and increased the activities of SOD and CAT in Müller cells in response to HG stimulation. Rhein decreased the production of VEGF, IL-1β, IL-6 and TNF-α. Moreover, Rhein attenuated HG-induced apoptosis, evidenced by increase in Bcl-2 level and decreases in the Bax, caspase-3 expression. It was also found that EX-527 counteracted Rhein-mediated anti-inflammatory, antioxidant and anti-apoptosis effects on Müller cells. The protein levels of p-AMPK and PGC-1α were also upregulated by Rhein. In conclusion, these findings support that Rhein may ameliorate HG-induced inflammation, oxidative stress, apoptosis and protect against mitochondrial dysfunction by the activation of the AMPK/Sirt1/PGC-1α signaling pathway.

High glucose induces HSP47 expression and promotes the secretion of inflammatory factors through the IRE1α/XBP1/HIF-1α pathway in retinal Müller cells

Diabetic retinopathy, a common complication of diabetes, is the leading cause of blindness globally. Müller cells are key players in diabetes-associated retinal inflammation and dysfunction. However, the pathological changes of Müller cells in response to high glucose (HG) and the underlying mechanism remain unclear. The aim of the present study was to investigate the key role of heat shock protein 47 (HSP47) in HG-induced unfolded protein and inflammatory responses. Primary mouse Müller cells were starved in serum-free DMEM overnight and then treated with HG (30 mM) for 0, 6, 12 or 24 h. It was observed that HG (30 mM) significantly induced the protein expression of HSP47, inositol-requiring transmembrane kinase and endonuclease-1α (IRE1α) and spliced X-box-binding protein 1 (XBP1s) in primary mouse Müller cells compared with the untreated group. In addition, the immunoprecipitation results revealed that HSP47 directly interacted with IRE1α, and this interaction was significantly enhanced by HG exposure for 12 or 24 h compared with the untreated group. Furthermore, small interfering RNA-mediated silencing of HSP47 significantly suppressed HG-induced activation of the IRE1α/XBP1s/hypoxia inducible factor-1 subunit α (HIF-1α) pathway and upregulation of the mRNA expression levels of the inflammatory cytokines vascular endothelial growth factor, platelet-derived growth factor subunit B, inducible nitric oxide synthase and angiopoietin-2 in Müller cells. Furthermore, overexpression of IRE1α or HIF-1α partially attenuated HSP47-siRNA-mediated inhibition of inflammatory cytokine expression in Müller cells. Collectively, these results indicated that HG may induce HSP47 expression and promote the inflammatory response through enhancing the interaction between HSP47 and IRE1α, and activating the IRE1α/XBP1s/HIF-1α pathway in retinal Müller cells.

The Impacts of Unfolded Protein Response in the Retinal Cells During Diabetes: Possible Implications on Diabetic Retinopathy Development

Diabetic retinopathy (DR) is a vision-threatening, chronic, and challenging eye disease in the diabetic population. Despite recent advancements in the clinical management of diabetes, DR remains the major cause of blindness in working-age adults. A better understanding of the molecular and cellular basis of DR development will aid in identifying therapeutic targets. Emerging pieces of evidence from recent research in the field of ER stress have demonstrated a close association between unfolded protein response (UPR)-associated cellular activities and DR development. In this minireview article, we shall provide an emerging understating of how UPR influences DR pathogenesis at the cellular level.

Modulating Expression of Thioredoxin Interacting Protein (TXNIP) Prevents Secondary Damage and Preserves Visual Function in a Mouse Model of Ischemia/Reperfusion

Retinal neurodegeneration, an early characteristic of several blinding diseases, triggers glial activation, resulting in inflammation, secondary damage and visual impairment. Treatments that aim only at neuroprotection have failed clinically. Here, we examine the impact of modulating thioredoxin interacting protein (TXNIP) to the inflammatory secondary damage and visual impairment in a model of ischemia/reperfusion (IR). Wild type (WT) and TXNIP knockout (TKO) mice underwent IR injury by increasing intraocular pressure for 40 min, followed by reperfusion. An additional group of WT mice received intravitreal TXNIP-antisense oligomers (ASO, 100 µg/2 µL) 2 days post IR injury. Activation of Müller glial cells, apoptosis and expression of inflammasome markers and visual function were assessed. IR injury triggered early TXNIP mRNA expression that persisted for 14 days and was localized within activated Müller cells in WT-IR, compared to sham controls. Exposure of Müller cells to hypoxia-reoxygenation injury triggered endoplasmic reticulum (ER) stress markers and inflammasome activation in WT cells, but not from TKO cells. Secondary damage was evident by the significant increase in the number of occluded acellular capillaries and visual impairment in IR-WT mice but not in IR-TKO. Intervention with TXNIP-ASO prevented ischemia-induced glial activation and neuro-vascular degeneration, and improved visual function compared to untreated WT. Targeting TXNIP expression may offer an effective approach in the prevention of secondary damage associated with retinal neurodegenerative diseases.