Calcium overload is a critical step in programmed necrosis of ARPE-19 cells induced by high-concentration H₂O₂

Review Article on Molecular Mechanism of Regulation of Hypertension by Macro-elements (Na, K, Ca and Mg), Micro-elements/Trace Metals (Zn and Cu) and Toxic Elements (Pb and As)

Hypertension (HT) is a medical condition arising due to increase in blood pressure (BP) prevalent worldwide. The balanced dietary intakes of macro-elements and micro-elements including Na, K, Ca, Mg, Zn, and Cu have been described to maintain BP in humans by regulating the osmolarity of blood, cells/tissues, prevention of generation of oxidative and nitrosative stress (OANS), and endothelial damage through their functioning as important components of renin-angiotensin-aldosterone system (RAAS), antioxidant enzyme defense system, and maintenance of blood vascular-endothelial and vascular smooth muscle cell (VSMC) functions. However, inadequate/excess dietary intakes of Na/K, Ca/Mg, and Zn/Cu along with higher Pb and As exposures recognized to induce HT through common mechanisms including the followings: endothelial dysfunctions due to impairment of vasodilatation, increased vasoconstriction and arterial stiffness, blood clotting, inflammation, modification of sympathetic activity and higher catecholamine release, increased peripheral vascular resistance, and cardiac output; increased OANS due to reduced and elevated activities of extracellular superoxide dismutase and NAD(P)H oxidase, less nitric oxide bioavailability, decrease in cGMP and guanylate cyclase activity, increase in intracellular Ca2+ ions in VSMCs, and higher pro-inflammatory cytokines; higher parathyroid and calcitriol hormones; activation/suppression of RAAS resulting imbalance in blood Na+, K+, and water regulated by renin, angiotensin II, and aldosterone through affecting natriuresis/kaliuresis/diuresis; elevation in serum cholesterol and LDL cholesterol, decrease in HDL cholesterol due to defect in lipoprotein metabolism. The present study recommends the need to review simple dietary mineral intervention studies/supplementation trials before keeping their individual dietary excess intakes/exposures in consideration because their interactions lead to elevation and fall of their concentrations in body affecting onset of HT.

Scaffolds with high oxygen content support osteogenic cell survival under hypoxia

Regeneration of large bone defects is a significant clinical challenge with variable success, but tissue engineering strategies are promising for rapid and effective bone regeneration. Maintaining an adequate oxygen level within implanted scaffolds is a major obstacle in bone tissue engineering. We developed a new oxygen-generating scaffold by electrospinning polycaprolactone with calcium peroxide (CaO2) nanocuboids (CPNCs) and characterized the physical, chemical, and biological properties of the resulting composites. Our scaffolds are highly porous and composed of submicron fibers that include CPNC as confirmed with XRD and FTIR analyses. Scaffolds containing CPNC provided controlled oxygen release for 14-days and supported cell proliferation while protecting preosteoblasts from hypoxia-induced cell death. Oxygen-generating scaffolds also facilitated bone mimetic defect contraction in vitro. The results suggest that our approach can be used to develop tissue-engineered products which target bone defects.

EYE-503: A Novel Retinoic Acid Drug for Treating Retinal Neurodegeneration

Retinal neurodegeneration is a major cause of vision loss. Retinoic acid signaling is critical for the maintenance of retinal function, and its dysfunction can cause retinal neurodegeneration. However, the therapeutic effects of retinoic acid drugs on retinal neurodegeneration remain unclear. In this study, we designed a novel retinoic acid drug called EYE-503 and investigated its therapeutic effects of EYE-503 on retinal neurodegeneration. The optic nerve crush (ONC) model was selected for the retinal neurodegeneration study. H&E staining, TUNEL staining, immunofluorescence staining, and visual electrophysiology assays were performed to determine the role of EYE-503 in retinal neurodegeneration in vivo. The CCK-8 assay, EdU incorporation assay, PI staining, and flow cytometry assays were performed to investigate the effects of EYE-503 administration on retinal neurodegeneration in vitro. The potential mechanism of EYE-503 in retinal neurodegeneration was investigated by network pharmacology and Western blots. The results showed that EYE-503 administration had no detectable cytotoxicity and tissue toxicity. EYE-503 administration alleviated ONC-induced retinal injury and optic nerve injury in vivo. EYE-503 administration attenuated retinal ganglion cell apoptosis, inhibited reactive gliosis, and retarded the progression of retinal neurodegeneration. Mechanistically, EYE-503 regulated retinal neurodegeneration by targeting the JNK/p38 signaling pathway. This study suggests that EYE-503 is a promising therapeutic agent for retinal neurodegenerative diseases.

Injectable Hydrogel Guides Neurons Growth with Specific Directionality

Visual disabilities affect more than 250 million people, with 43 million suffering from irreversible blindness. The eyes are an extension of the central nervous system which cannot regenerate. Neural tissue engineering is a potential method to cure the disease. Injectability is a desirable property for tissue engineering scaffolds which can eliminate some surgical procedures and reduce possible complications and health risks. We report the development of the anisotropic structured hydrogel scaffold created by a co-injection of cellulose nanofiber (CNF) solution and co-polypeptide solution. The positively charged poly (L-lysine)-r-poly(L-glutamic acid) with 20 mol% of glutamic acid (PLLGA) is crosslinked with negatively charged CNF while promoting cellular activity from the acid nerve stimulate. We found that CNF easily aligns under shear forces from injection and is able to form hydrogel with an ordered structure. Hydrogel is mechanically strong and able to support, guide, and stimulate neurite growth. The anisotropy of our hydrogel was quantitatively determined in situ by 2D optical microscopy and 3D X-ray tomography. The effects of PLLGA:CNF blend ratios on cell viability, neurite growth, and neuronal signaling are systematically investigated in this study. We determined the optimal blend composition for stimulating directional neurite growth yielded a 16% increase in length compared with control, reaching anisotropy of 30.30% at 10°/57.58% at 30°. Using measurements of calcium signaling in vitro, we found a 2.45-fold increase vs. control. Based on our results, we conclude this novel material and unique injection method has a high potential for application in neural tissue engineering.

Carnosine Counteracts the Molecular Alterations Aβ Oligomers-Induced in Human Retinal Pigment Epithelial Cells

Age-related macular degeneration (AMD) has been described as a progressive eye disease characterized by irreversible impairment of central vision, and unfortunately, an effective treatment is still not available. It is well-known that amyloid-beta (Aβ) peptide is one of the major culprits in causing neurodegeneration in Alzheimer's disease (AD). The extracellular accumulation of this peptide has also been found in drusen which lies under the retinal pigment epithelium (RPE) and represents one of the early signs of AMD pathology. Aβ aggregates, especially in the form of oligomers, are able to induce pro-oxidant (oxidative stress) and pro-inflammatory phenomena in RPE cells. ARPE-19 is a spontaneously arising human RPE cell line validated for drug discovery processes in AMD. In the present study, we employed ARPE-19 treated with Aβ oligomers, representing an in vitro model of AMD. We used a combination of methods, including ATPlite, quantitative real-time PCR, immunocytochemistry, as well as a fluorescent probe for reactive oxygen species to investigate the molecular alterations induced by Aβ oligomers. In particular, we found that Aβ exposure decreased the cell viability of ARPE-19 cells which was paralleled by increased inflammation (increased expression of pro-inflammatory mediators) and oxidative stress (increased expression of NADPH oxidase and ROS production) along with the destruction of ZO-1 tight junction protein. Once the damage was clarified, we investigated the therapeutic potential of carnosine, an endogenous dipeptide that is known to be reduced in AMD patients. Our findings demonstrate that carnosine was able to counteract most of the molecular alterations induced by the challenge of ARPE-19 with Aβ oligomers. These new findings obtained with ARPE-19 cells challenged with Aβ1-42 oligomers, along with the well-demonstrated multimodal mechanism of action of carnosine both in vitro and in vivo, able to prevent and/or counteract the dysfunctions elicited by Aβ oligomers, substantiate the neuroprotective potential of this dipeptide in the context of AMD pathology.

Protrusion of KCNJ13 Gene Knockout Retinal Pigment Epithelium Due to Oxidative Stress–Induced Cell Death

Purpose

This study was performed to elucidate the mechanisms of morphological abnormalities in a Leber congenital amaurosis 16 (LCA16) cell model using KCNJ13 knockout (KO) retinal pigment epithelial cells derived from human iPS cells (hiPSC-RPE).

Methods

In KCNJ13 KO and wild-type hiPSC-RPE cells, ZO-1 immunofluorescence was performed, and confocal images were captured. The area and perimeter of each cell were measured. To detect cell death, ethidium homodimer III (EthD-III) staining and LDH assay were used. Scanning electron microscopy (SEM) was used to observe the cell surface. The expression levels of oxidative stress-related genes were examined by quantitative PCR. To explore the effects of oxidative stress, tert-butyl hydroperoxide (t-BHP) was administered to the hiPSC-RPE cells. Cell viability was tested by MTS assay, whereas oxidative damage was monitored by oxidized (GSSG) and reduced glutathione levels.

Results

The area and perimeter of KCNJ13-KO hiPSC-RPE cells were enlarged. EthD-III-positive cells were increased with more dead cells in the protruded region. The KO RPE had significantly higher LDH levels in the medium. SEM observations revealed aggregated cells having broken cell surfaces on the KO RPE sheet. The KCNJ13-deficient RPE showed increased expression levels of oxidative stress-related genes and total glutathione levels. Furthermore, t-BHP induced a significant increase in cell death and GSSG levels in the KO RPE.

Conclusions

We suggest that in the absence of the Kir.7.1 potassium channel, human RPE cells are vulnerable to oxidative stress and ultimately die. The dying/dead cells form aggregates and protrude from the surviving KCNJ13-deficient RPE sheet.

Citrulline protects human retinal pigment epithelium from hydrogen peroxide and iron/ascorbate induced damages

Oxidative stress plays an important role in the ageing of the retina and in the pathogenesis of retinal diseases such as age‐related macular degeneration (ARMD). Hydrogen peroxide is a reactive oxygen species generated by the photo‐excited lipofuscin that accumulates during ageing in the retinal pigment epithelium (RPE), and the age‐related accumulation of lipofuscin is associated with ARMD. Iron also accumulates with age in the RPE that may contribute to ARMD as an important source of oxidative stress. The aim of this work was to investigate the effects of L‐Citrulline (CIT), a naturally occurring amino acid with known antioxidant properties, on oxidative stressed cultured RPE cells. Human RPE (ARPE‐19) cells were exposed to hydrogen peroxide (H₂O₂) or iron/ascorbate (I/A) for 4 h, either in the presence of CIT or after 24 h of pretreatment. Here, we show that supplementation with CIT protects ARPE‐19 cells against H₂O₂ and I/A. CIT improves cell metabolic activity, decreases ROS production, limits lipid peroxidation, reduces cell death and attenuates IL‐8 secretion. Our study evidences that CIT is able to protect human RPE cells from oxidative damage and suggests potential protective effect for the treatment of retinal diseases associated with oxidative stress.

Molecular Mechanisms of Retinal Pigment Epithelium Dysfunction in Age-Related Macular Degeneration

The retinal pigment epithelium (RPE), situated upon Bruch’s membrane, plays multiple roles in the ocular system by interacting with photoreceptors and. Therefore, dysfunction of the RPE causes diseases related to vision loss, such as age-related macular degeneration (AMD). Despite AMD being a global cause of blindness, the pathogenesis remains unclear. Understanding the pathogenesis of AMD is the first step for its prevention and treatment. This review summarizes the common pathways of RPE dysfunction and their effect in AMD. Potential treatment strategies for AMD based on targeting the RPE have also been discussed.

ATR prevents Ca2+ overload-induced necrotic cell death through phosphorylation-mediated inactivation of PARP1 without DNA damage signaling

Hyperactivation of PARP1 is known to be a major cause of necrotic cell death by depleting NAD⁺/ATP pools during Ca²⁺ overload which is associated with many ischemic diseases. However, little is known about how PARP1 hyperactivity is regulated during calcium overload. In this study we show that ATR kinase, well known for its role in DNA damage responses, suppresses ionomycin, glutamate, or quinolinic acid‐induced necrotic death of cells including SH‐SY5Y neuronal cells. We found that the inhibition of necrosis requires the kinase activity of ATR. Specifically, ATR binds to and phosphorylates PARP1 at Ser179 after the ionophore treatments. This site‐specific phosphorylation inactivates PARP1, inhibiting ionophore‐induced necrosis. Strikingly, all of this occurs in the absence of detectable DNA damage and signaling up to 8 hours after ionophore treatment. Furthermore, little AIF was released from mitochondria/cytoplasm for nuclear import, supporting the necrotic type of cell death in the early period of the treatments. Our results reveal a novel ATR‐mediated anti‐necrotic mechanism in the cellular stress response to calcium influx without DNA damage signaling.

Oxidative and Nitrosative Stress in Age-Related Macular Degeneration: A Review of Their Role in Different Stages of Disease

Although the exact pathogenetic mechanisms leading to age-related macular degeneration (AMD) have not been clearly identified, oxidative damage in the retina and choroid due to an imbalance between local oxidants/anti-oxidant systems leading to chronic inflammation could represent the trigger event. Different in vitro and in vivo models have demonstrated the involvement of reactive oxygen species generated in a highly oxidative environment in the development of drusen and retinal pigment epithelium (RPE) changes in the initial pathologic processes of AMD; moreover, recent evidence has highlighted the possible association of oxidative stress and neovascular AMD. Nitric oxide (NO), which is known to play a key role in retinal physiological processes and in the regulation of choroidal blood flow, under pathologic conditions could lead to RPE/photoreceptor degeneration due to the generation of peroxynitrite, a potentially cytotoxic tyrosine-nitrating molecule. Furthermore, the altered expression of the different isoforms of NO synthases could be involved in choroidal microvascular changes leading to neovascularization. The purpose of this review was to investigate the different pathways activated by oxidative/nitrosative stress in the pathogenesis of AMD, focusing on the mechanisms leading to neovascularization and on the possible protective role of anti-vascular endothelial growth factor agents in this context.

Sunitinib and Imatinib Display Differential Cardiotoxicity in Adult Rat Cardiac Fibroblasts That Involves a Role for Calcium/Calmodulin Dependent Protein Kinase II

Background: Tyrosine kinase inhibitors (TKIs) have dramatically improved cancer treatment but are known to cause cardiotoxicity. The pathophysiological consequences of TKI therapy are likely to manifest across different cell types of the heart, yet there is little understanding of the differential adverse cellular effects. Cardiac fibroblasts (CFs) play a pivotal role in the repair and remodeling of the heart following insult or injury, yet their involvement in anti-cancer drug induced cardiotoxicity has been largely overlooked. Here, we examine the direct effects of sunitinib malate and imatinib mesylate on adult rat CF viability, Ca²⁺ handling and mitochondrial function that may contribute to TKI-induced cardiotoxicity. In particular, we investigate whether Ca²⁺/calmodulin dependent protein kinase II (CaMKII), may be a mediator of TKI-induced effects. Methods: CF viability in response to chronic treatment with both drugs was assessed using MTT assays and flow cytometry analysis. Calcium mobilization was assessed in CFs loaded with Fluo4-AM and CaMKII activation via oxidation was measured via quantitative immunoblotting. Effects of both drugs on mitochondrial function was determined by live mitochondrial imaging using MitoSOX red. Results: Treatment of CFs with sunitinib (0.1-10 μM) resulted in concentration-dependent alterations in CF phenotype, with progressively significant cell loss at higher concentrations. Flow cytometry analysis and MTT assays revealed increased cell apoptosis and necrosis with increasing concentrations of sunitinib. In contrast, equivalent concentrations of imatinib resulted in no significant change in cell viability. Both sunitinib and imatinib pre-treatment increased Angiotensin II-induced intracellular Ca²⁺ mobilization, with only sunitinib resulting in a significant effect and also causing increased CaMKII activation via oxidation. Live cell mitochondrial imaging using MitoSOX red revealed that both sunitinib and imatinib increased mitochondrial superoxide production in a concentration-dependent manner. This effect in response to both drugs was suppressed in the presence of the CaMKII inhibitor KN-93. Conclusions: Sunitinib and imatinib showed differential effects on CFs, with sunitinib causing marked changes in cell viability at concentrations where imatinib had no effect. Sunitinib caused a significant increase in Angiotensin II-induced intracellular Ca²⁺ mobilization and both TKIs caused increased mitochondrial superoxide production. Targeted CaMKII inhibition reversed the TKI-induced mitochondrial damage. These findings highlight a new role for CaMKII in TKI-induced cardiotoxicity, particularly at the level of the mitochondria, and confirm differential off-target toxicity in CFs, consistent with the differential selectivity of sunitinib and imatinib.

Spermidine Attenuates Oxidative Stress-Induced Apoptosis via Blocking Ca2+ Overload in Retinal Pigment Epithelial Cells Independently of ROS

Retinal pigment epithelial (RPE) cells occupy the outer layer of the retina and perform various biological functions. Oxidative damage to RPE cells is a major risk factor for retinal degeneration that ultimately leads to vision loss. In this study, we investigated the role of spermidine in a hydrogen peroxide (H₂O₂)-induced oxidative stress model using human RPE cells. Our findings showed that 300 μM H₂O₂ increased cytotoxicity, apoptosis, and cell cycle arrest in the G2/M phase, whereas these effects were markedly suppressed by 10 μM spermidine. Furthermore, spermidine significantly reduced H₂O₂-induced mitochondrial dysfunction including mitochondrial membrane potential and mitochondrial activity. Although spermidine displays antioxidant properties, the generation of intracellular reactive oxygen species (ROS) upon H₂O₂ insult was not regulated by spermidine. Spermidine did suppress the increase in cytosolic Ca²⁺ levels resulting from endoplasmic reticulum stress in H₂O₂-stimulated human RPE cells. Treatment with a cytosolic Ca²⁺ chelator markedly reversed H₂O₂-induced cellular dysfunction. Overall, spermidine protected against H₂O₂-induced cellular damage by blocking the increase of intracellular Ca²⁺ independently of ROS. These results suggest that spermidine protects RPE cells from oxidative stress, which could be a useful treatment for retinal diseases.

Age-Related Macular Degeneration: Role of Oxidative Stress and Blood Vessels

Age-related macular degeneration (AMD) is a common irreversible ocular disease characterized by vision impairment among older people. Many risk factors are related to AMD and interact with each other in its pathogenesis. Notably, oxidative stress and choroidal vascular dysfunction were suggested to be critically involved in AMD pathogenesis. In this review, we give an overview on the factors contributing to the pathophysiology of this multifactorial disease and discuss the role of reactive oxygen species and vascular function in more detail. Moreover, we give an overview on therapeutic strategies for patients suffering from AMD.

Not All Stressors Are Equal: Mechanism of Stressors on RPE Cell Degeneration

Age-related macular degeneration (AMD) is a major cause of irreversible blindness among the elderly population. Dysfunction and degeneration of the retinal pigment epithelial (RPE) layer in the retina underscore the pathogenesis of both dry and wet AMD. Advanced age, cigarette smoke and genetic factors have been found to be the prominent risk factors for AMD, which point to an important role for oxidative stress and aging in AMD pathogenesis. However, the mechanisms whereby oxidative stress and aging lead to RPE cell degeneration are still unclear. As cell senescence and cell death are the major outcomes from oxidative stress and aging, here we review the mechanisms of RPE cell senescence and different kinds of cell death, including apoptosis, necroptosis, pyroptosis, ferroptosis, with an aim to clarify how RPE cell degeneration could occur in response to AMD-related stresses, including H₂O₂, 4-Hydroxynonenal (4-HNE), N-retinylidene-N-retinyl-ethanolamine (A2E), Alu RNA and amyloid β (Aβ). Besides those, sodium iodate (NaIO₃) induced RPE cell degeneration is also discussed in this review. Although NaIO₃ itself is not related to AMD, this line of study would help understand the mechanism of RPE degeneration.

Sublethal exposure of small few-layer graphene promotes metabolic alterations in human skin cells

Small few-layer graphene (sFLG), a novel small-sized graphene-related material (GRM), can be considered as an intermediate degradation product of graphene. GRMs have a promising present and future in the field of biomedicine. However, safety issues must be carefully addressed to facilitate their implementation. In the work described here, the effect of sub-lethal doses of sFLG on the biology of human HaCaT keratinocytes was examined. A one-week treatment of HaCaTs with sub-lethal doses of sFLG resulted in metabolome remodeling, dampening of the mitochondrial function and a shift in the redox state to pro-oxidant conditions. sFLG raises reactive oxygen species and calcium from 24 h to one week after the treatment and this involves the activation of NADPH oxidase 1. Likewise, sFLG seems to induce a shift from oxidative phosphorylation to glycolysis and promotes the use of glutamine as an alternative source of energy. When sub-toxic sFLG exposure was sustained for 30 days, an increase in cell proliferation and mitochondrial damage were observed. Further research is required to unveil the safety of GRMs and degradation-derived products before their use in the workplace and in practical applications.

Retinal pigment epithelium and age-related macular degeneration: A review of major disease mechanisms

Age‐related macular degeneration (AMD) is a progressive degenerative disease that is the leading cause of vision loss in the elderly population. Degeneration/dysregulation of the retinal pigment epithelium (RPE), a supportive monolayer of cells underlying the photoreceptors, is commonly seen in patients with AMD. While treatment exists for the neovascular/wet form of AMD, there is currently no cure for the non‐exudative/dry form of AMD, making it imperative to understand the pathogenesis of this disease. Although our understanding of the aetiology of AMD has increased over the years, the underlying disease mechanism has not yet been identified, mainly due to the multifactorial nature of this disease. Herein, we review some of the commonly proposed degeneration pathways of RPE cells and their role in the pathogenesis of AMD; including activation of the complement cascade, oxidative stress‐induced cell death mechanisms, dysfunctional mitochondria and the role of crystallins in AMD disease progression.

Di-(2-ethyl hexyl) phthalate induces necroptosis in chicken cardiomyocytes by triggering calcium overload

Di-(2-ethyl hexyl)phthalate (DEHP) is a kind of plasticizer that can cause cardiovascular disorders in animals, but its specific mechanism of action has not been determined. We aimed to investigate whether taxifolin (TAX) can antagonize the cytotoxicity of DEHP on cardiomyocytes. Chicken cardiomyocytes were treated with DEHP (500 μM) and/or TAX (0.5 μM) for 24 h. Ca²⁺ staining showed that the concentration of Ca²⁺ in the cytoplasm of cardiomyocytes was significantly increased under DEHP stimulation. However, in the DEHP + TAX group, the Ca²⁺ concentration was largely restored. In addition, the results of necroptosis--fluorescent and flow cytometry analysis showed that the DEHP group had severe necroptosis compared with the control group. The necrotic rate in the DEHP + TAX group was significantly lower than that in the DEHP group. At the mRNA and protein levels, the expression of the necrotic-calcium pathway genes RIPK1, RIPK3, MLKL, FAS, Caspase-8, CAMKII, and SERCA in the DEHP group increased to varying degrees relative to the control group. However, TAX improved this injury. Compared with the DEHP group, the expression of these genes was significantly decreased in the DEHP + TAX group. The present study indicate that DEHP could trigger cardiomyocyte necroptosis through Ca²⁺ overload, which could be alleviated by TAX.

Mitochondria as Potential Targets and Initiators of the Blue Light Hazard to the Retina

Commercially available white light-emitting diodes (LEDs) have an intense emission in the range of blue light, which has raised a range of public concerns about their potential risks as retinal hazards. Distinct from other visible light components, blue light is characterized by short wavelength, high energy, and strong penetration that can reach the retina with relatively little loss in damage potential. Mitochondria are abundant in retinal tissues, giving them relatively high access to blue light, and chromophores, which are enriched in the retina, have many mitochondria able to absorb blue light and induce photochemical effects. Therefore, excessive exposure of the retina to blue light tends to cause ROS accumulation and oxidative stress, which affect the structure and function of the retinal mitochondria and trigger mitochondria-involved death signaling pathways. In this review, we highlight the essential roles of mitochondria in blue light-induced photochemical damage and programmed cell death in the retina, indicate directions for future research and preventive targets in terms of the blue light hazard to the retina, and suggest applying LED devices in a rational way to prevent the blue light hazard.

A derivative of betulinic acid protects human Retinal Pigment Epithelial (RPE) cells from cobalt chloride-induced acute hypoxic stress

The Retinal Pigment Epithelium (RPE) is a monolayer of cells located above the choroid. It mediates human visual cycle and nourishes photoreceptors. Hypoxia-induced oxidative stress to RPE is a vital cause of retinal degeneration such as the Age-related Macular Degeneration. Most of these retinal diseases are irreversible with no efficient treatment, therefore protecting RPE cells from hypoxia stress is an important way to prevent or slow down the progression of retinal degeneration. Betulinic acid (BA) and betulin (BE) are pentacyclic triterpenoids with anti-oxidative property, but little is known about their effect on RPE cells. We investigated the protective effect of BA, BE and their derivatives against cobalt chloride-induced hypoxia stress in RPE cells. Human ARPE-19 cells were exposed to BA, BE and their eighteen derivatives (named as H3H20) that we customized through replacing moieties at C3 and C28 positions. We found that cobalt chloride reduced cell viability, increased Reactive Oxygen Species (ROS) production as well as induced apoptosis and necrosis in ARPE-19 cells. Interestingly, the pretreatment of 3-O-acetyl-glycyl- 28-O-glycyl-betulinic acid effectively protected cells from acute hypoxia stress induced by cobalt chloride. Our immunoblotting results suggested that this derivative attenuated the cobalt chloride-induced activation of Akt, Erk and JNK pathways. All findings were further validated in human primary RPE cells. In summary, this BA derivate has protective effect against the acute hypoxic stress in human RPE cells and may be developed into a candidate agent effective in the prevention of prevalent retinal diseases.

Oxidative stress induces ferroptotic cell death in retinal pigment epithelial cells

The dysfunction and cell death of retinal pigment epithelial (RPE) cells are hallmarks of late-stage dry (atrophic) age-related macular degeneration (AMD), for which no effective therapy has yet been developed. Previous studies have indicated that iron accumulation is a source of excess free radical production in RPE, and age-dependent iron accumulation in RPE is accelerated in patients with dry AMD. Although the pathogenic role of oxidative stress in RPE in the development of dry AMD is widely accepted, the mechanisms of oxidative stress-induced RPE cell death remain elusive. Here, we show that ferroptotic cell death, a mode of regulated necrosis mediated by iron and lipid peroxidation, is implicated in oxidative stress-induced RPE cell death in vitro. In ARPE-19 cells we observed that the ferroptosis inhibitors ferrostatin-1 and deferoxamine (DFO) rescued tert-butyl hydroperoxide (tBH)-induced RPE cell death more effectively than inhibitors of apoptosis or necroptosis. tBH-induced RPE cell death was accompanied by the three characteristics of ferroptotic cell death: lipid peroxidation, glutathione depletion, and ferrous iron accumulation, which were all significantly attenuated by ferrostatin-1 and DFO. Exogenous iron overload enhanced tBH-induced RPE cell death, but this effect was also attenuated by ferrostatin-1 and DFO. Furthermore, mRNA levels of numerous genes known to regulate iron metabolism were observed to be influenced by oxidative stress. Taken together, our observations suggest that multiple modes of cell death are involved in oxidative stress-induced RPE cell death, with ferroptosis playing a particularly important role.

Glutathione depletion induces ferroptosis, autophagy, and premature cell senescence in retinal pigment epithelial cells

Glutathione (GSH) protects against oxidative damage in many tissues, including retinal pigment epithelium (RPE). Oxidative stress-mediated senescence and death of RPE and subsequent death of photoreceptors have been observed in age-related macular degeneration (AMD). Although the consequences of GSH depletion have been described previously, questions remain regarding the molecular mechanisms. We herein examined the downstream effects of GSH depletion on stress-induced premature senescence (SIPS) and cell death in human RPE cells. Briefly, cultured ARPE-19 cells were depleted of GSH using: (1) incubation in cystine (Cys₂)-free culture medium; (2) treatment with buthionine sulphoximine (BSO, 1000 µM) to block de novo GSH synthesis for 24-48 h; or (3) treatment with erastin (10 µM for 12-24 h) to inhibit Cys₂/glutamate antiporter (system x_c^-). These treatments decreased cell viability and increased both soluble and lipid reactive oxygen species (ROS) generation but did not affect mitochondrial ROS or mitochondrial mass. Western blot analysis revealed decreased expression of ferroptotic modulator glutathione peroxidase 4 (GPX4). Increased autophagy was apparent, as reflected by increased LC3 expression, autophagic vacuoles, and autophagic flux. In addition, GSH depletion induced SIPS, as evidenced by increased percentage of the senescence-associated β-galactosidase-positive cells, increased senescence-associated heterochromatin foci (SAHF), as well as cell cycle arrest at the G1 phase. GSH depletion-dependent cell death was prevented by selective ferroptosis inhibitors (8 μM Fer-1 and 600 nM Lip-1), iron chelator DFO (80 μM), as well as autophagic inhibitors Baf-A1 (75 nM) and 3-MA (10 mM). Inhibiting autophagy with Baf-A1 (75 nM) or 3-MA (10 mM) promoted SIPS. In contrast, inducing autophagy with rapamycin (100 nM) attenuated SIPS. Our findings suggest that GSH depletion induces ferroptosis, autophagy, and SIPS. In addition, we found that autophagy is activated in the process of ferroptosis and reduces SIPS, suggesting an essential role of autophagy in ferroptosis and SIPS.

Differential effects of graphene materials on the metabolism and function of human skin cells

Graphene-related materials (GRMs) such as graphene oxide (GO) and few-layer graphene (FLG) are used in multiple biomedical applications; however, there is still insufficient information available regarding their interactions with the main biological barriers such as skin. In this study, we explored the effects of GO and FLG on HaCaTs human skin keratinocytes, using NMR-based metabolomics and fluorescence microscopy to evaluate the global impact of each GRM on cell fate and damage. GO and FLG at low concentrations (5 μg mL-1) induced a differential remodeling of the metabolome, preceded by an increase in the level of radical oxygen species (ROS) and free cytosolic Ca2+. These changes are linked to a concentration-dependent increase in cell death by triggering apoptosis and necrosis, the latter being predominant at higher concentrations of the nanostructures. In addition, both compounds reduce the ability of HaCaT cells to heal wounds. Our results demonstrate that the GO and FLG used in this study, which mainly differ in their oxidation state, slightly trigger differential effects on HaCaTs cells, but with evident outcomes at the cellular and molecular levels. Their behavior as pro-apoptotic/necrotic substances and their ability to inhibit cell migration, even at low doses, should be considered in the development of future applications.

Study on Chemical Profile and Neuroprotective Activity of Myrica rubra Leaf Extract

The chemical profile of Myrica rubra (a native species in China) leaf extract was investigated by UPLC-PDA-HRMS, and the neuroprotective activity of two characteristic constituents, myricanol and myricetrin, was evaluated with N2a cells using H₂O₂-inducedoxidative challenge through a series of methods, e.g., MTT assay, ROS assay and [Ca2+]i assay. Among the 188 constituents detected in the extract of Myrica rubra leaf, 116 were identified definitely or tentatively by the comprehensive utilization of precise molecular weight and abundant multistage fragmentation information obtained by quadrupole orbitrap mass spectrometry. In addition, 14 potential new compounds were reported for the first time. This work established an example for the research of microconstituents in a complex analyte and revealed that suppression of H₂O₂-induced cytotoxicity in N2a cells was achieved by the pretreatment with myricanol. The evidence suggested myricanol may potentially serve as a remedy for prevention and therapy of neurodegenerative diseases induced by oxidative stress.

Esculetin Neutralises Cytotoxicity of t-BHP but Not of H2O2 on Human Leukaemia NB4 Cells

The coumarin esculetin shows antioxidant action on some cell types, both by scavenging ROS and by decreasing ROS production. We have previously demonstrated the induction of apoptosis by esculetin on NB4 human leukaemia cells by an ill-defined mechanism related to ROS levels. In this work, we analyze the effect of the simultaneous treatment with esculetin and two oxidants to observe the early events in the mechanism of esculetin-induced apoptosis. Our results show that, from the early time of 15 min, esculetin acts synergistically with H₂O₂ to decrease cell viability and metabolic activity and to increase apoptosis in NB4 cells. In contrast, the early oxidative effects of t-BHP are neutralised by esculetin, protecting human leukaemia NB4 cells from apoptosis. Esculetin seems to restrict the increase in peroxides caused by H₂O₂ or t-BHP in the time interval analyzed. These results contribute to a better understanding of the cytotoxic effect caused by esculetin on NB4 cells. At the same time, the early neutralisation of exogenous oxidants could be of interest to prevent diseases related to oxidative stress imbalance.

Calcium alterations signal either to senescence or to autophagy induction in stem cells upon oxidative stress

Intracellular calcium ([Ca2+]i) has been reported to play an important role in autophagy, apoptosis and necrosis, however, a little is known about its impact in senescence. Here we investigated [Ca2+]i contribution to oxidative stress-induced senescence of human endometrium-derived stem cells (hMESCs). In hMESCs sublethal H2O2-treatment resulted in a rapid calcium release from intracellular stores mediated by the activation of PLC/IP3/IP3R pathway. Notably, further senescence development was accompanied by persistently elevated [Ca2+]i levels. In H2O2-treated hMESCs, [Ca2+]i chelation by BAPTA-AM (BAPTA) was sufficient to prevent the expansion of the senescence phenotype, to decrease endogenous reactive oxygen species levels, to avoid G0/G1 cell cycle arrest, and finally to retain proliferation. Particularly, loading with BAPTA attenuated phosphorylation of the main DNA damage response members, including ATM, 53BP1 and H2A.X and reduced activation of the p53/p21/Rb pathway in H2O2-stimulated cells. Next, we revealed that BAPTA induced an early onset of AMPK-dependent autophagy in H2O2-treated cells as confirmed by both the phosphorylation status of AMPK/mTORC1 pathway and the dynamics of the LC3 lipidization. Summarizing the obtained data we can assume that calcium chelation is able to trigger short-term autophagy and to prevent the premature senescence of hMESCs under oxidative stress.

Calcium Signaling During Meiotic Cell Cycle Regulation and Apoptosis in Mammalian Oocytes

Calcium (Ca⁺⁺ ) is one of the major signal molecules that regulate various aspects of cell functions including cell cycle progression, arrest, and apoptosis in wide variety of cells. This review summarizes current knowledge on the differential roles of Ca⁺⁺ in meiotic cell cycle resumption, arrest, and apoptosis in mammalian oocytes. Release of Ca⁺⁺ from internal stores and/or Ca⁺⁺ influx from extracellular medium causes moderate increase of intracellular Ca⁺⁺ ([Ca⁺⁺ ]i) level and reactive oxygen species (ROS). Increase of Ca⁺⁺ as well as ROS levels under physiological range trigger maturation promoting factor (MPF) destabilization, thereby meiotic resumption from diplotene as well as metaphase-II (M-II) arrest in oocytes. A sustained increase of [Ca⁺⁺ ]i level beyond physiological range induces generation of ROS sufficient enough to cause oxidative stress (OS) in aging oocytes. The increased [Ca⁺⁺ ]i triggers Fas ligand-mediated oocyte apoptosis. Further, OS triggers mitochondria-mediated oocyte apoptosis in several mammalian species. Thus, Ca⁺⁺ exerts differential roles on oocyte physiology depending upon its intracellular concentration. A moderate increase of [Ca⁺⁺ ]i as well as ROS mediate spontaneous resumption of meiosis from diplotene as well as M-II arrest, while their high levels cause meiotic cell cycle arrest and apoptosis by operating both mitochondria- as well as Fas ligand-mediated apoptotic pathways. Indeed, Ca⁺⁺ regulates cellular physiology by modulating meiotic cell cycle and apoptosis in mammalian oocytes. J. Cell. Physiol. 232: 976-981, 2017. © 2016 Wiley Periodicals, Inc.

Optochemokine Tandem for Light-Control of Intracellular Ca2

An optochemokine tandem was developed to control the release of calcium from endosomes into the cytosol by light and to analyze the internalization kinetics of G-protein coupled receptors (GPCRs) by electrophysiology. A previously constructed rhodopsin tandem was re-engineered to combine the light-gated Ca²⁺-permeable cation channel Channelrhodopsin-2(L132C), CatCh, with the chemokine receptor CXCR4 in a functional tandem protein tCXCR4/CatCh. The GPCR was used as a shuttle protein to displace CatCh from the plasma membrane into intracellular areas. As shown by patch-clamp measurements and confocal laser scanning microscopy, heterologously expressed tCXCR4/CatCh was internalized via the endocytic SDF1/CXCR4 signaling pathway. The kinetics of internalization could be followed electrophysiologically via the amplitude of the CatCh signal. The light-induced release of Ca²⁺ by tandem endosomes into the cytosol via CatCh was visualized using the Ca²⁺-sensitive dyes rhod2 and rhod2-AM showing an increase of intracellular Ca²⁺ in response to light.

In vivo observation of the pH alternation in mitochondria for various external stimuli

The pH of mitochondria (pHm) has a close relationship with many biological processes. Here we developed a new indicator Mito-pH-1 for the ratiometric fluorescence detection of the mitochondria pH value, which has excellent tolerance to environmental change. And Mito-pH-1 has been used for the first time to monitor the change of pHm under temperature and H2O2 stimuli in living cells.

Cellular and molecular mechanistic insight into the DNA-damaging potential of few-layer graphene in human primary endothelial cells

Despite graphene being proposed for a multitude of biomedical applications, there is a dearth in the fundamental cellular and molecular level understanding of how few-layer graphene (FLG) interacts with human primary cells. Herein, using human primary umbilical vein endothelial cells as model of vascular transport, we investigated the basic mechanism underlying the biological behavior of graphene. Mechanistic toxicity studies using a battery of cell based assays revealed an organized oxidative stress paradigm involving cytosolic reactive oxygen stress, mitochondrial superoxide generation, lipid peroxidation, glutathione oxidation, mitochondrial membrane depolarization, enhanced calcium efflux, all leading to cell death by apoptosis/necrosis. We further investigated the effect of graphene interactions using cDNA microarray analysis and identified potential adverse effects by down regulating key genes involved in DNA damage response and repair mechanisms. Single cell gel electrophoresis assay/Comet assay confirmed the DNA damaging potential of graphene towards human primary cells.

Diosmetin protects against retinal injury via reduction of DNA damage and oxidative stress

Visual impairment is a global public health problem that needs new candidate drugs. Chrysanthemum is a traditional Chinese drug, famous for its eye-protective function, with an unclear mechanism of action. To determine how chrysanthemum contributes to vision, we identified, for the first time, the component of chrysanthemum, diosmetin (DIO), which acts in protecting the injured retina in an adriamycin (ADR) improving model. We observed that DIO could attenuate the apoptosis of retinal cells in Sprague–Dawley rats and verified this effect in cultured human retinal pigment epithelium (RPE) cells, ARPE-19. Our further study on the mechanism revealed the counteractive effect of DIO on the attenuation of DNA damage and oxidative stress, which occurs in a wide range of retinal disorders. These results collectively promise the potential value of DIO as a retinal-protective agent for disorders that lead to blindness. In addition, we identified, for the first time, the component of chrysanthemum, DIO, which acts in protecting the injured retina.

RPE necroptosis in response to oxidative stress and in AMD

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly. The underlying mechanism of non-neovascular AMD (dry AMD), also named geographic atrophy (GA) remains unclear and the mechanism of retinal pigment epithelial (RPE) cell death in AMD is controversial. We review the history and recent progress in understanding the mechanism of RPE cell death induced by oxidative stress, in AMD mouse models, and in AMD patients. Due to the limitation of toolsets to distinguish between apoptosis and necroptosis (or necrosis), most previous research concludes that apoptosis is a major mechanism for RPE cell death in response to oxidative stress and in AMD. Recent studies suggest necroptosis as a major mechanism of RPE cell death in response to oxidative stress. Moreover, ultrastructural and histopathological studies support necrosis as major mechanism of RPE cells death in AMD. In this review, we discuss the mechanism of RPE cell death in response to oxidative stress, in AMD mouse models, and in human AMD patients. Based on the literature, we hypothesize that necroptosis is a major mechanism for RPE cell death in response to oxidative stress and in AMD.

4-Acetoxyphenol Prevents RPE Oxidative Stress-Induced Necrosis by Functioning as an NRF2 Stabilizer

PURPOSE

Oxidative stress has been suggested to be a major risk factor for the pathogenesis of AMD. Retinal pigment epithelial (RPE) cells are essential for maintaining the homeostasis of the retina, and RPE cell death and the resultant photoreceptor apoptosis have been observed in dry AMD, especially in geographic atrophy. The purpose of this article was to identify and repurpose the Food and Drug Administration-approved natural compound 4-Acetoxyphenol (4-AC), and to evaluate its effect and mechanism in protecting against oxidative stress-induced RPE necrosis.

METHODS

We exposed ARPE-19 cells to tert-Butyl hydroperoxide (tBHP) after pretreatment with 4-AC, and measured cell viability by MTT assay. Aggregation of RIPK3 and HMGB1 nuclear release were analyzed by transfected reporter genes. Reactive oxygen species (ROS) were measured using a commercially available ROS detection system. The importance of the NRF2/NQO1/HO-1 pathway in mediating 4-AC function was corroborated by siRNA studies, qRT-PCR, and immunostaining.

RESULTS

We have identified a natural antioxidant, 4-AC, which demonstrates strong abilities to protect RPE cells from oxidative stress-induced necrosis. Mechanistically, 4-AC blocked the increase of cellular ROS induced by oxidative stress, and upregulated NQO1 and HO-1 genes by stabilizing and inducing the nuclear translocation of NRF2 transcription factor. The NQO1, HO-1, and NRF2 were further shown to be required for 4-AC protection of RPE cells from death induced by tBHP. The tBHQ, an NRF2 stabilizer, consistently mimicked the protective effect of 4-AC against tBHP-induced RPE death.

CONCLUSIONS

The compound 4-AC protects ARPE-19 cells from oxidative stress-induced necrosis through upregulation of NQO1 and HO-1 genes by stabilization of NRF2.

Na(+)-Ca(2+) exchanger targeting miR-132 prevents apoptosis of cardiomyocytes under hypoxic condition by suppressing Ca(2+) overload

During ischemia-reperfusion (IR) injury of the heart, Ca(2+) overload occurs, leading to cardiomyocyte dysfunction and eventual cell death by apoptosis. Since preventing Ca(2+) overload during IR injury has been reported to protect cardiomyocytes, interrupting Ca(2+) signaling cascades leading to Ca(2+) overload may exert protective effect on cardiomyocytes under hypoxic condition. One of the key regulators of the intracellular Ca(2+) level during IR injury is Na(+)-Ca(2+) exchanger 1 (NCX1), whose down-regulation during IR injury conferred protection of heart. In the present study, we examined whether down-regulation of NCX1 using exogenous microRNA ameliorates apoptosis of cardiomyocytes under hypoxic condition. Here, we identified miR-132 as a novel microRNA targeting the NCX1, whose expression increased during hypoxia. Delivery of miR-132 suppressed the increase of intracellular Ca(2+) in cardiomyocytes under hypoxia, and the expressions of apoptotic molecules, such as Bax, cytochrome C, and caspase 3, and the number of apoptotic cells were also decreased by exogenous miR-132 treatment. These results suggest the potential of miR-132 as an effective therapeutic agent against IR damage to heart by preventing Ca(2+) overload during hypoxic condition and warrant further studies to validate its anti-apoptotic effect in vivo.

Gossypol Acetic Acid Prevents Oxidative Stress-Induced Retinal Pigment Epithelial Necrosis by Regulating the FoxO3/Sestrin2 Pathway

The late stage of dry age-related macular degeneration (AMD), or geographic atrophy (GA), is characterized by extensive retinal pigment epithelial (RPE) cell death, and a cure is not available currently. We have recently demonstrated that RPE cells die from necrosis in response to oxidative stress, providing a potential novel mechanism for RPE death in AMD. In this study, we screened U.S. Food and Drug Administration-approved natural compounds and identified gossypol acetic acid (GAA) as a potent inhibitor of oxidative stress-induced RPE cell death. GAA induces antioxidative response and inhibits accumulation of excessive reactive oxygen species in cells, through which it prevents the activation of intrinsic necrotic pathway in response to oxidative stress. Sestrin2 (SESN2) is found to mediate GAA function in antioxidative response and RPE survival upon oxidative stress. Moreover, Forkhead box O3 transcription factor (FoxO3) is further found to be required for GAA-mediated SESN2 expression and RPE survival. Mechanistically, GAA promotes FoxO3 nuclear translocation and binding to the SESN2 enhancer, which in turn increases its transcriptional activity. Taken together, we have identified GAA as a potent inhibitor of oxidative stress-induced RPE necrosis by regulating the FoxO3/SESN2 pathway. This study may have significant implications in the therapeutics of age-related diseases, especially GA.

[Application of the Ca2+ indicator fluo-3 and fluo-4 in the process of H2O2 induced apoptosis of A549 cell]

BACKGROUND AND OBJECTIVE

Lung cancer is a common malignant tumor all over the world, and Ca(2+) is a critical regulator for apoptosis of cancer cells. The monitoring of cytoplastic Ca(2+) level in real-time will contribute to further investigate the molecular mechanisms of apoptosis mediated by Ca2+ in lung cancer cells. To evaluate the Ca(2+) indicator fluo-3 and fluo-4 in the process of H2O2 induced the apoptosis of lung adenocarcinoma A549 cells. The cytoplastic Ca(2+) concentration ([Ca(2+)]i) was determined in real-time, and the correlations between [Ca(2+)]i and cell apoptosis were investigated. The differences in fluorescence intensity and measured value were compared between the two Ca(2+) indicators.

METHODS

Cells were loaded with the Ca(2+) indicator fluo-3 or fluo-4 for 1 h, and then stimulated with 50 mM H2O2. Laser scanning confocal microscope was applied to perform real-time monitoring on the variation of [Ca(2+)]i in selected cells. DAPI staining was used to observe apoptosis in H2O2 treated cells.

RESULTS

Our results showed that the fluorescence intensity of fluo-4 was stronger than that of fluo-3 in the same condition of dye concentration, loading time and image acquisition parameters before or after H2O2 stimulation. The cytoplastic [Ca(2+)]i was rapidly elevated in H2O2 stimulated A549 cells. The range of [Ca(2+)]i in selected cells loaded with fluo-3 was 112.2 nM-1,069.6 nM, and that in selected cells loaded with fluo-4 was 7.6 nM-505.4 nM. Moreover, the apoptotic rate was significantly increased in H2O2 treated cells, compared with untreated ones (P<0.01).

CONCLUSION

In summary, H2O2 promoted Ca(2+) release in A549 cells, and induced cell apoptosis. Ca(2+) indicator fluo-4 was probably more applicable to measure [Ca(2+)]i in cells with less content of Ca(2+).

Calcium entry via connexin hemichannels in lens epithelium

Exposure to hyposmotic solution causes release of ATP from lens cells via hemichannels. Because hemichannel opening feasibly could swamp the cells with calcium, we carried out studies to measure the magnitude of the increase in cytoplasmic calcium concentration caused by hemichannel opening. In studies on porcine lens epithelial cells in primary culture, propidium iodide (PI) uptake was measured as an index of hemichannel opening. PI uptake was increased significantly in cells exposed to hyposmotic solution. The PI increase under hyposmotic conditions was suppressed by GAP 27, a connexin inhibitor peptide. In studies on cells loaded with Fura-2, continuous exposure to hyposmotic solution caused a cytoplasmic calcium concentration increase that peaked within ∼30 s then remained elevated at or below the peak response for more than 60 min. The peak calcium concentration was 186 ± 2.3 nM compared to a baseline value of 98.0 ± 1.4 nM. The calcium concentration increased a lot further in cells exposed to A23187 (2.5 μM) or the sodium-calcium exchange inhibitor SN-6 (10 μM) added after the onset of the calcium rise in hyposmotic solution. The cytoplasmic calcium increase in hyposmotic solution was abolished by GAP 27. Calcium returned to baseline in cells exposed to hyposmotic solution then treated with GAP 27 starting 2 min after the onset of the calcium rise. The calcium increase in hyposmotic solution did not occur when calcium was eliminated from the bathing medium. The responses to hyposmotic and hyperosmotic stress were different. There was no detectable increase in calcium or PI entry in cells exposed to hyperosmotic solution (500mOsm). In summary, GAP 27-sensitive accumulation of PI by cultured lens epithelium points to connexin hemichannel opening and associated calcium entry. Even though connexins form channels with a large carrying capacity, calcium entry does not increase the cytoplasmic calcium concentration beyond a tolerable physiological range.

Acetylcholinesterase function in apoptotic retina pigment epithelial cells induced by H2O2

AIM

To investigate the acetylcholinesterase (AChE) expression involved in retina pigment epithelial (RPE) apoptosis induced by higher concentrations H2O2.

METHODS

The human retinal pigment epithelium cell line ARPE-19 was from ATCC (Rockville, MD). Cultured ARPE-19 cells were treated with H2O2 at 0, 250, 500, 1 000, 2 000µmol/L and cell viability was measured with MTT assay. AChE expression and DNA fragments were analyzed by immunocytochemistry, TUNEL and PARP-1 Western blotting.

RESULTS

Immunofluorescence detected AChE exist in the normal human retinal tissue. When H2O2 >500µmol/L, AChE expression showed an increase after 2h, and this concentration was selected for the present study. RPE cell was induced with 1 000µmol/L H2O2 for 2h, compared to the control group, cell activity decline detected by MTT, AChE and PARP-1 protein expression was significantly increased detected by Western blotting. AChE immunofluorescence staining was positive in RPE cell after H2O2 incubate 2h. In addition, pretreatment with 100µmol/L epigallocatechin gallate (EGCG), cell viability increased from 31.20%±3.90% to 70.23%±12.96%.

CONCLUSION

AChE is weakly expressed in normal human RPE cells. Stimulation with H2O2 caused the stable increase of AChE expression in RPE cells, which may indicate that AChE may be an important role in AMD.

Induction of necrotic cell death by oxidative stress in retinal pigment epithelial cells

Age-related macular degeneration (AMD) is a degenerative disease of the retina and the leading cause of blindness in the elderly. Retinal pigment epithelial (RPE) cell death and the resultant photoreceptor apoptosis are characteristic of late-stage dry AMD, especially geographic atrophy (GA). Although oxidative stress and inflammation have been associated with GA, the nature and underlying mechanism for RPE cell death remains controversial, which hinders the development of targeted therapy for dry AMD. The purpose of this study is to systematically dissect the mechanism of RPE cell death induced by oxidative stress. Our results show that characteristic features of apoptosis, including DNA fragmentation, caspase 3 activation, chromatin condensation and apoptotic body formation, were not observed during RPE cell death induced by either hydrogen peroxide or tert-Butyl hydroperoxide. Instead, this kind of cell death can be prevented by RIP kinase inhibitors necrostatins but not caspase inhibitor z-VAD, suggesting necrotic feature of RPE cell death. Moreover, ATP depletion, receptor interacting protein kinase 3 (RIPK3) aggregation, nuclear and plasma membrane leakage and breakdown, which are the cardinal features of necrosis, were observed in RPE cells upon oxidative stress. Silencing of RIPK3, a key protein in necrosis, largely prevented oxidative stress-induced RPE death. The necrotic nature of RPE death is consistent with the release of nuclear protein high mobility group protein B1 into the cytoplasm and cell medium, which induces the expression of inflammatory gene TNFα in healthy RPE and THP-1 cells. Interestingly, features of pyroptosis or autophagy were not observed in oxidative stress-treated RPE cells. Our results unequivocally show that necrosis, but not apoptosis, is a major type of cell death in RPE cells in response to oxidative stress. This suggests that preventing oxidative stress-induced necrotic RPE death may be a viable approach for late-stage dry AMD.

Effect of ionized serum calcium on outcomes in acute kidney injury needing renal replacement therapy: secondary analysis of the acute renal failure trial network study

BACKGROUND

Hypocalcemia is very common in critically ill patients. While the effect of ionized calcium (iCa) on outcome is not well understood, manipulation of iCa in critically ill patients is a common practice. We analyzed all-cause mortality and several secondary outcomes in patients with acute kidney injury (AKI) by categories of serum iCa among participants in the Acute Renal Failure Trial Network (ATN) Study.

METHODS

This is a post hoc secondary analysis of the ATN Study which was not preplanned in the original trial. Risk of mortality and renal recovery by categories of iCa were compared using multiple fixed and adjusted time-varying Cox regression models. Multiple linear regression models were used to explore the impact of baseline iCa on days free from ICU and hospital.

RESULTS

A total of 685 patients were included in the analysis. Mean age was 60 (SD=15) years. There were 502 male patients (73.3%). Sixty-day all-cause mortality was 57.0%, 54.8%, and 54.4%, in patients with an iCa<1, 1-1.14, and ≥1.15 mmol/L, respectively (p=0.87). Mean of days free from ICU or hospital in all patients and the 28-day renal recovery in survivors to Day 28 were not significantly different by categories of iCa. The hazard for death in a fully adjusted time-varying Cox regression survival model was 1.7 (95% CI: 1.3-2.4) comparing iCa<1 to iCa≥1.15 mmol/L. No outcome was different for levels of iCa>1 mmol/L.

CONCLUSION

Severe hypocalcemia with iCa<1 mmol/L independently predicted mortality in patients with AKI needing renal replacement therapy.

Retinal deimination and PAD2 levels in retinas from donors with age-related macular degeneration (AMD)

Deimination is a form of protein posttranslational modification carried out by the peptidyl arginine deiminases (PADs) enzymes. PAD2 is the principal deiminase expressed in the retina. Elevated levels of PAD2 and protein deimination are present in a number of human neurological diseases, with or without ocular manifestation. To define the association of deimination with the pathogenesis of age-related macular degeneration (AMD), we studied protein deimination and PAD2 levels in retinas of AMD donor eyes compared to age-matched non-AMD retinas. Eyes from non-AMD and AMD donors were fixed in 4% paraformaldehyde and 0.5% glutaraldehyde in phosphate buffer. Retina and retinal pigment epithelium (RPE) from donor eyes were processed for immunohistochemical detection and western blotting using antibodies to PAD2 and citrulline residues. The ganglion cell, inner plexiform, inner nuclear and outer nuclear layers were labeled by both PAD2 and citrulline antibodies. Changes in the localization of deiminated residues and PAD2 were evident as the retinal layers were remodeled coincident with photoreceptor degeneration in AMD retinas. Immunodetection of either PAD2 or citrulline residues could not be evaluated in the RPE layer due to the high autofluorescence levels in this layer. Interestingly, higher deimination immunoreactivity was detected in AMD retinal lysates. However, no significant changes in PAD2 were detected in the AMD and non-AMD retinas and RPE lysates. Our observations show increased levels of protein deimination but not PAD2 in AMD retinas and RPE, suggesting a reduced rate of turnover of deiminated proteins in these AMD retinas.

Daily calcium intake and its relation to blood pressure, blood lipids, and oxidative stress biomarkers in hypertensive and normotensive subjects

Several studies revealed that low calcium intake is related to high prevalence of cardiovascular diseases such as hypertension. The prevalence of hypertension is high in Koreans along with their low dietary calcium consumption. Thus, the aim of this study was to evaluate the status of calcium intake between the hypertension and normotension groups and to investigate the correlation between dietary calcium intake and blood pressure, blood lipid parameters, and blood/urine oxidative stress indices. A total of 166 adult subjects participated in this study and were assigned to one of two study groups: a hypertension group (n = 83) who had 140 mmHg or higher in systolic blood pressure (SBP) or 90 mmHg or higher in diastolic blood pressure (DBP), and an age- and sex-matched normotension group (n = 83, 120 mmHg or less SBP and 80 mmHg or less DBP). The hypertension group consumed 360.5 mg calcium per day, which was lower than that of the normotension group (429.9 mg) but not showing significant difference. In the hypertension group, DBP had a significant negative correlation with plant calcium (P < 0.01) after adjusting for age, gender, body mass index (BMI), and energy intake. In the normotension group, total calcium and animal calcium intake were significantly and positively correlated with serum triglycerides. No significant relationship was found between calcium intake and blood/urine oxidative stress indices in both groups. Overall, these data suggest reconsideration of food sources for calcium consumption in management of the blood pressure or blood lipid profiles in both hypertensive and normotensive subjects.

Calcium imaging in gentamicin ototoxicity: increased intracellular calcium relates to oxidative stress and late apoptosis

OBJECTIVES

To estimate intracellular calcium changes in gentamicin (GM) ototoxicity using calcium imaging. To investigate GM-induced physiologic changes in auditory cells including cell viability, apoptosis, and oxidative stress.

METHODS

Varying concentrations of GM were applied to the HEI-OC1 cochlear cell line. Calcium imaging tracked changes in intracellular calcium concentration during GM cytotoxicity. Cell viability and intracellular reactive oxygen species (ROS) levels also were measured.

RESULTS

Little change in calcium levels occurred in HEI-OC1 cells exposed to less than 35 mM GM. However, calcium rose continuously in cells exposed to more than 60 mM GM. With administration of intermediate concentrations of 40 or 50 mM GM, calcium increased variably in different cells, returning to baseline in some cases, or rising continuously in others. Upon increase of GM concentration, intracellular calcium concentration and ROS were increased, and cell viability was decreased due to late apoptosis.

CONCLUSION

This study shows that GM increased intracellular calcium, ROS, and late apoptosis of HEI-OC1 cells derived from cochlear tissue. Increase of intracellular calcium is related to GM-induced apoptosis and oxidative stress. Calcium imaging can be used to determine change of intracellular calcium concentrations and apoptosis in GM ototoxicity.

Calcium binding protein-mediated regulation of voltage-gated calcium channels linked to human diseases

Calcium ion entry through voltage-gated calcium channels is essential for cellular signalling in a wide variety of cells and multiple physiological processes. Perturbations of voltage-gated calcium channel function can lead to pathophysiological consequences. Calcium binding proteins serve as calcium sensors and regulate the calcium channel properties via feedback mechanisms. This review highlights the current evidences of calcium binding protein-mediated channel regulation in human diseases.