The Effect of A2E on the Ca<sup>2+</sup>-PKC Signaling Pathway in Human RPE Cells Exposed to Blue Light

Luo, Maomei; Wang, Shu; Tang, Yun; Zeng, Chun; Cai, Shanjun

doi:https://doi.org/10.1155/2022/2233223

Journal of Ophthalmology

On this page

Abstract Background Methods Results Discussion Conclusion Abbreviations Data Availability Disclosure Conflicts of Interest Authors’ Contributions Acknowledgments References Copyright Related Articles

Research Article | Open Access

Volume 2022 | Article ID 2233223 | https://doi.org/10.1155/2022/2233223

The Effect of A2E on the Ca²⁺-PKC Signaling Pathway in Human RPE Cells Exposed to Blue Light

Maomei Luo,^1,2,3Shu Wang,^1,3Yun Tang,³Chun Zeng,^1,3and Shanjun Cai^1,3

Academic Editor: Ana Raquel Santiago

Received02 Mar 2022

Accepted30 Aug 2022

Published18 Oct 2022

Abstract

Aims. In a model of blue light-induced damage in N-retinylidene-N-retinylethanolamine (A2E)-loaded human retinal pigment epithelial (RPE) cells, we examined the effect of A2E on the calcium (Ca²⁺)-protein kinase C (PKC) signaling pathway. Methods. Primary human RPE cells were cultured, and the cells in the 4th–6th passages were used in this study. The cells were divided into 5 groups: control cells (no A2E, no blue light), blue light-treated cells, blue light + chloroquine-treated cells, blue light + A2E-treated cells, and blue light + A2E + chloroquine-treated cells. The cells were first treated with chloroquine (15 μM for 12 h) and then loaded with A2E (25 μM for 2 h).The blue light intensity was 2000 ± 500 lux, and the duration was 6 h. After blue light exposure, the cells were cultured for 24 h. Fluo-3/AM staining was used to determine the level of cytoplasmic Ca²⁺, and the cells were photographed using a laser scanning confocal microscope to analyze the fluorescence intensity. The intracellular levels of inositol triphosphate (IP3) and diacylglycerol (DAG) were measured by enzyme-linked immunosorbent assay (ELISA). Intracellular PKC activity was measured with a nonradioactive nuclide assay. Results. Among all cell groups, the levels of Ca²⁺, DAG, and IP3 were lowest in the control cells (). The Ca²⁺, DAG, and IP3 levels in the blue light + A2E-treated cells and blue light + chloroquine-treated cells were higher than those in the blue light-treated cells (). The Ca²⁺, DAG, and IP3 levels were highest in the blue light + A2E + chloroquine-treated group (). PKC activity was lowest in the control cells (). The PKC activity of the blue light + A2E-treated cells and blue light + chloroquine-treated cells was higher than that of the blue light-treated cells (), and the PKC activity of the blue light + A2E + chloroquine-treated cells was the highest (). Conclusion. Blue light and A2E increased the levels of Ca²⁺, IP3, and DAG in human RPE cells and enhanced PKC activity, and blue light and A2E had a synergistic effect. Chloroquine further increased the levels of Ca²⁺, IP3, and DAG and PKC activity in RPE cells or A2E-loaded RPE cells exposed to blue light.

1. Background

Retinal pigment epithelial (RPE) cells are an important part of the blood–retinal barrier. These cells maintain retinal homeostasis by filtering damaging light, replenishing 11-cis retinal pigment clusters in photoreceptors, and engulfing the outer disc membrane of receptors. RPE lipofuscin is a byproduct of the phagocytosis of lipid-rich photoreceptor outer segments, and the major fluorophore is N-retinylidene-N-retinylethanolamine (A2E), which increases with age and is not easily degraded [1]. When A2E is irradiated by visible light or ultraviolet light, its structure changes, and free radicals such as superoxide anions, singlet oxygen, and hydrogen peroxide are produced; these free radicals can damage the structure of the cells [2].

In modern society, mobile phones, tablets, and computers emit high-energy blue light. The most harmful component of visible light is blue light (400–500 nm) [3]. Blue light can damage the function of RPE cells and reduce the reaction of photoreceptors to light. Toxic substances (e.g., A2E) produced by blue light irradiation are related to the development of degenerative diseases, such as age-related macular degeneration (AMD) and Stargardt’s disease [4, 5].

Calcium (Ca²⁺) is an important second messenger in cells. Extracellular free Ca²⁺ levels are much higher than those within the cell, and more than 90% of Ca²⁺ is found in intracellular Ca²⁺ stores [6]. A rapid increase in the Ca²⁺ concentration in the plasma membrane or intracellular Ca²⁺ stores can trigger a chain reaction and a series of physiological effects. Protein kinase C (PKC), a target molecule of Ca²⁺ in the cell, is usually present in its inactive form. When extracellular signals activate phospholipase C (PLC) through receptors and decompose membrane phospholipids, inositol triphosphate (IP3) and diacylglycerol (DAG) are produced [7]. IP3 promotes the release of Ca²⁺ from Ca²⁺ stores, resulting in an increase in the intracellular Ca²⁺ concentration, which activates PKC.

Therefore, we utilized the autophagy function of lysosomes and the effect of chloroquine on lysosomal stability to explore the phototoxic effects of A2E on intracellular Ca²⁺, IP3, and DAG levels and PKC activity in the Ca²⁺-PKC signaling pathway during blue light irradiation.

2. Methods

2.1. Cell Sources and Ethics Statement

Human primary RPE cells were cultured, and three donor eyeballs were obtained after corneal transplantation in the Department of Ophthalmology, Affiliated Hospital of Zunyi Medical University. All experiments were approved by the Ethics Committee of Zunyi Medical University, China ([2017]1–111).

2.2. Reagents and Instruments

Dulbecco’s modified Eagle’s medium (DMEM), fetal bovine serum (FBS), and a trypsin-EDTA solution (0.25%) were purchased from Gibco (Logan, UT, USA). Penicillin–streptomycin was purchased from HyClone (Logan, UT, USA). Fluo-3/AM was purchased from Thermo Scientific (Waltham, MA, USA). Enzyme-linked immunosorbent assay (ELISA) kits were purchased from Jianglai Biotechnology (Baoshan, Shanghai, China). A PKC kinase activity assay kit was purchased from Promega (Madison, WI, USA). A2E was donated by the First Affiliated Hospital of Shanghai Jiaotong University.

2.3. Primary Human RPE Cell Culture and Treatment

Briefly, the eyeballs were cut approximately 5-6 mm behind the corneal limbus, and the anterior segment, vitreous body, and retinal neuroepithelial layer were carefully removed to make an eye cup, which was then washed with HBSS. Approximately 2/3 of the eye cup was filled with 0.25% trypsin, and the eyeballs were incubated at 37°C for 30 min. DMEM containing 10% FBS was used to stop the reaction, and the cell suspension was collected and centrifuged at 1000 r/min for 8 min. The precipitate was resuspended in DMEM supplemented with 15% FBS, and the cells were cultured in a 25 cm² cell culture flask at a density of 3 × 10⁴ cells/ml. When the cells reached approximately 80% confluence, they were passaged at a dilution of 1 : 2. Cells from the same passage were used for each experiment. Cells cultured in DMEM without other treatments were considered control cells. Cells illuminated with blue light were named blue light-treated cells. Cells that were exposed to blue light and chloroquine, A2E, or chloroquine plus A2E were named blue light + chloroquine-treated cells, blue light + A2E-treated cells, and blue light + A2E + chloroquine-treated cells, respectively. Chloroquine at a final concentration of 15 μM was added to the cells and incubated for 12 h. Then, 25 μM A2E was added to the cells and incubated in the dark for 2 h before the cells were illuminated [8]. The blue light intensity was 2000 ± 500 lux, and the duration was 6 h; illumination was followed by culture for 24 h [9].

2.4. Immunofluorescence Analysis

RPE cells were fixed for 10 min with 4% paraformaldehyde. After being rinsed in PBS, the cells were blocked with 1% Triton X-100 and 10% goat serum at room temperature for 30 min, followed by incubation with mouse anti-human RPE65 antibodies overnight at 4°C and goat anti-mouse IgG secondary antibodies for 1 h at 37°C. 4′,6-Diamidino-2-phenylindole (DAPI) was used for nuclear staining. Immunoreactive cells were visualized, and images were recorded using an inverted confocal microscope.

2.5. Intracellular Ca²⁺ Detection

Ca²⁺ levels were measured using the fluorescent probe Fluo-3/AM. Briefly, Fluo-3/AM was dissolved in DMSO and diluted with HBSS to a final concentration of 5 μM in the dark. After treatment, the cells were washed and stained with Fluo-3/AM for 45 min at 37°C in the dark. The fluorescence intensity of Ca²⁺ was quantified with a laser scanning confocal microscope at an excitation wavelength of 488 nm and an emission wavelength of 525 nm.

2.6. Determination of Intracellular IP3 and DAG Levels

The cells were grouped and pretreated as described in Section 2.5. The supernatants and cells were collected, and the levels of IP3 and DAG were measured using commercial ELISA kits according to the manufacturer’s instructions. The absorbance at 450 nm was measured with a microplate reader.

2.7. Determination of Intracellular PKC Activity

PKC activity was measured using a PKC activity assay kit according to the manufacturer’s protocol. Cells were homogenized and centrifuged to isolate the proteins, a cellulose column was used to separate the PKC fraction, and an agarose gel was used for electrophoresis to separate the two different PKC proteins (phosphorylated PKC and nonphosphorylated PKC). The ratio of the gray value of phosphorylated PKC to that of nonphosphorylated PKC indicated the level of PKC activity (PKC activation).

2.8. Statistical Analysis

The results are expressed as the mean ± SD of at least three biological replicates. Statistical analysis was performed with SPSS 18.0, and comparisons between two groups were performed with one-way ANOVA followed by the LSD test. A P value less than 0.05 was considered to indicate statistical significance.

3. Results

3.1. Immunofluorescence Analysis of Human RPE Cells

The primary human RPE cells were spindle-shaped with many cytoplasmic pigment particles. The fourth-generation human RPE cells were polygonal or irregular in shape, and the number of cytoplasmic pigment granules was decreased. Immunofluorescence staining was used to characterize the expression of RPE-specific biomarkers, and the results showed green fluorescence in the RPE cells, indicating the expression of RPE65 (Figure 1).

(a)

(b)

(c)

3.2. Levels of Cytoplasmic Ca²⁺

Ca²⁺ in the cytoplasm was labeled with Fluo-3/AM, and the fluorescence intensity was measured using a laser scanning confocal microscope. We found that among that in other cells, the level of Ca²⁺ in the control cells was the lowest (). The Ca²⁺ level in the blue light + A2E + chloroquine-treated cells was higher than that in the other cells (). The increase in Ca²⁺ levels was more significant in the blue light + A2E-treated cells and blue light + chloroquine-treated cells than in the blue light-treated cells () (Figure 2).

Figure 2

The cytoplasmic Ca²⁺ level. To determine the Ca²⁺ level in the cytoplasm, the fluorescence intensity of Ca²⁺ in RPE cells was assessed by confocal microscopy using the Ca²⁺-sensitive dye Fluo-3/AM. Scale bar = 20 µm. The graph shows the quantified data. The data are presented as the mean ± SD (n = 3). An LSD test was conducted following one-way ANOVA. vs. control cells; ^# vs. blue light-treated cells; and ^& vs. blue light + chloroquine-treated cells; ^▲ vs. blue light + A2E-treated cells.

3.3. The Levels of IP3 and DAG in RPE Cells

The intracellular levels of IP3 and DAG were measured by ELISA and found to be lower in control cells than in the other cells (). Compared with the other cells, the blue light + A2E + chloroquine-treated cells had the highest levels of IP3 and DAG (). The levels of IP3 and DAG in the blue light + A2E-treated cells and blue light + chloroquine-treated cells were higher than those in the blue light-treated cells () (Figure 3).

(a)

(b)

3.4. PKC Activity in RPE Cells

Intracellular PKC activity was measured with a nonradioactive nuclide assay, which showed that PKC activity was lower in the control group than in the other groups (). The blue light-treated cells exhibited decreased PKC activity compared with that in the blue light + A2E-treated cells and blue light + chloroquine-treated cells (). Blue light + A2E + chloroquine-treated cells exhibited the highest PKC activity () (Figure 4).

4. Discussion

AMD is a progressive blinding disease with no cure and is the main cause of visual disability in industrialized countries [10–12]. Increasing evidence has shown that mitochondrial and RPE cells damage plays important roles in the pathogenesis of AMD [13]. RPE cells participate in phototransduction, and blue light is the most harmful factor to RPE cells [14]. RPE cells can also internalize the outer membrane disc of photoreceptors with the participation of CD36 and MerTK and begin to degrade these factors through the autophagy/lysosome pathway [15, 16], but undegraded residue accumulates in RPE cells in the form of lipofuscin, which leads to RPE cell senescence and apoptosis [17, 18]. A2E is the main fluorescent substance associated with lipofuscin. Through indirect photooxidation, A2E can damage lysosomes, increase lysosomal membrane permeability, and trigger inflammation [19, 20]. Therefore, we examined the effects of A2E on intracellular Ca²⁺, IP3, and DAG levels and PKC activity in the Ca²⁺-PKC signaling pathway during blue light irradiation.

Ca²⁺ is a second messenger that regulates various physiological and pathological functions, such as secretion, contraction, metabolism, gene transcription, and cell death [21]. Intracellular Ca²⁺ homeostasis is an important factor for maintaining normal cell function. Changes in intracellular Ca²⁺ concentrations determine cell survival or death. Close contact between the ER, plasma membrane, and other intracellular organelles participates in controlling Ca²⁺ homeostasis.

PKC regulates a variety of cellular processes by participating in the inositol phosphate signaling pathway [22]. All members of the PKC family are composed of an N-terminal regulatory region and a C-terminal catalytic domain connected by a protein-sensitive hinge zone. PKC exists in the cytoplasm and is generally inactive. This protein is water-soluble in its inactive state and free in the cytosol, but it becomes a membrane-bound enzyme after activation [23]. The activation of PKC is lipid-dependent and requires the presence of DAG, as well as an increase in the cytosolic Ca²⁺ concentration [24].

When A2E accumulates to a certain extent in the lysosomes of RPE cells, the phototoxicity of A2E increases the permeability of the lysosomal membrane [25], which releases a variety of acidic enzymes into the cytoplasm, inducing reactive oxygen species (ROS) generation and apoptosis [26, 27]. In this study, Ca²⁺ levels in blue light-treated cells and blue light + A2E-treated cells were higher than those in control cells, and Ca²⁺ levels in blue light + A2E-treated cells were higher than those in blue light-treated cells, indicating that blue light and A2E synergistically increased intracytoplasmic Ca²⁺ levels. After human RPE cells are exposed to A2E and/or blue light, these stimuli activate PLC through tyrosine protein kinase, stimulatory G proteins, or other pathways. PLC catalyzes the cleavage of phosphatidylinositol-4,5-bisphosphate (PIP2) in the membrane to produce IP3 and DAG. IP3 is water-soluble and binds the IP3 receptor on the endoplasmic reticulum membrane to release Ca²⁺ into the cytoplasm, resulting in an increase in intracellular Ca²⁺ levels. DAG is a fat-soluble molecule that reduces the level of Ca²⁺ required for PKC activation and synergizes with Ca²⁺ to activate PKC [28]. Cells undergo apoptosis in response to continuous exposure to high concentrations of free Ca²⁺ [29]. PKC can phosphorylate serine and threonine residues on various proteins and then promote cell proliferation and apoptosis [30, 31]. Our results showed that blue light and A2E increased cytoplasmic Ca²⁺ levels in human RPE cells and increased the activity of PKC, thereby inducing RPE cell apoptosis.

Chloroquine is a lipophilic weak base with a pH of approximately 7.4 that exists in three forms: unprotonated (CQ), singly protonated (CQ+), and diprotonated (CQ++) forms [32, 33]. Chloroquine, which is commonly used to prevent malaria, also inhibits autophagy by inhibiting the activity of lysosomal enzymes by changing the pH level [33]. Lysosomal inhibition can begin with the degradation of LAMP-2 in the glycocalyx, which decreases phagocytic uptake and increases exocytosis, leading lysosomal hydrolases to leak into the cytosol [34]. When lysosomal permeability increases or lysosomes rupture, released cathepsins B and D can cleave BCL-2 family proteins, which can cause mitochondrial dysfunction and activate the caspase-mediated apoptosis pathway [35, 36]. Chloroquine can also induce the accumulation of lipid bodies, which may contribute to drusen formation and the mechanism of AMD [34]. In this study, the levels of Ca²⁺, DAG, and IP3 and PKC activity in blue light + chloroquine-treated cells were higher than those in blue light-treated cells, and the levels in blue light + A2E + chloroquine-treated cells were higher than those in blue light + A2E-treated cells. After the addition of chloroquine, the pH of the acidic lysosomes in the cell changed, and lysosome homeostasis was destroyed. In vitro, chloroquine can destabilize lysosomal membranes and promote the release of lysosomal enzymes and other substances, such as A2E and Ca²⁺, within cells [37, 38]. As a result, Ca²⁺, IP3, and DAG levels in the cytoplasm increase, which activates PKC, and minor leakage can lead to caspase-dependent or caspase-independent apoptosis, while the massive translocation of lysosomal proteases can cause necrosis [37].

5. Conclusion

In the present study, we found that blue light and A2E could increase the levels of Ca²⁺, IP3, and DAG in human RPE cells and enhance the activity of PKC; furthermore, these factors were found to have a synergistic effect. Chloroquine further increased the levels of Ca²⁺, IP3, and DAG and PKC activity in human RPE cells exposed to blue light and/or loaded with A2E. However, our observations have some limitations. The blue light was a common denominator in our study of the additive effects of A2E and/or chloroquine. Since no A2E-only controls were used, the effect of A2E alone on the levels of Ca²⁺, IP3, and DAG and PKC activity could not be explored, and evidence that chloroquine increases lysosomal permeability is scarce, which requires further investigation.

Abbreviations

A2E:	N-Retinylidene-N-retinylethanolamine
RPE:	Retinal pigment epithelial
PKC:	Protein kinase C
IP3:	Inositol triphosphate
DAG:	Diacylglycerol.

Data Availability

The data used to support the findings of this study are available from the corresponding author upon request.

Disclosure

Mao-Mei Luo and Shu Wang are the co-first authors.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Authors’ Contributions

Mao-Mei Luo and Shu Wang contributed equally to this work.

Acknowledgments

The authors thank the Cell Engineering Laboratory and Anesthesia Laboratory of Zunyi Medical University and Shanghai General Hospital (Shanghai First People’s Hospital) of Shanghai Jiaotong University for their supply of experimental reagents. This work was supported by grants from the National Natural Science Foundation of China, 2017 (81760174).

References

H. Takeshima, E. Venturi, and R. Sitsapesan, “Rebecca Sitsapesan New and notable ion-channels in the sarcoplasmic/endoplasmic reticulum: do they support the process of intracellular Ca²⁺ release?” Journal of Physiology, vol. 593, no. 15, pp. 3241–3251, 2015.
View at: Publisher Site | Google Scholar
A. Iriyama, Y. Inoue, H. Takahashi, Y. Tamaki, W. D. Jang, and Y. Yanagi, “A2E, a component of lipofuscin, is pro-angiogenic in vivo,” Journal of Cellular Physiology, vol. 220, no. 2, pp. 469–475, 2009.
View at: Publisher Site | Google Scholar
N. Leveziel, C. Delcourt, J. Zerbib et al., “[Epidemiology of age related macular degeneration],” Journal Français d'Ophtalmologie, vol. 32, no. 6, pp. 440–451, 2009.
View at: Publisher Site | Google Scholar
R. E. Marc, B. W. Jones, C. B. Watt, F. Vazquez-Chona, D. K. Vaughan, and D. T. Organisciak, “Extreme retinal remodeling triggered by light damage: implications for age related macular degeneration,” Molecular Vision, vol. 14, pp. 782–806, 2008.
View at: Google Scholar
Lt Adler, N. P. Boyer, C. Chen, Z. Ablonczy, R. K. Crouch, and Y. Koutalos, “The 11-cis retinal origins of lipofuscin in the retina,” Prog Mol Biol Transl Sci, vol. 134, pp. e1–12, 2015.
View at: Publisher Site | Google Scholar
C. Costas-Ferreira and L. R. F. Faro, “Systematic review of calcium channels and intracellular calcium signaling: relevance to pesticide neurotoxicity,” International Journal of Molecular Sciences, vol. 22, no. 24, p. 13376, 2021.
View at: Publisher Site | Google Scholar
W. Xu, Q. Zhu, S. Liu et al., “Calretinin participates in regulating steroidogenesis by PLC-Ca(2+)-PKC pathway in leydig cells,” Scientific Reports, vol. 8, no. 1, p. 7403, 2018.
View at: Publisher Site | Google Scholar
B. Lu, P. Zhang, M. Zhou et al., “Involvement of XBP1s in blue light-induced a2e-containing retinal pigment epithelium cell death,” Ophthalmic Research, vol. 57, no. 4, pp. 252–262, 2017.
View at: Publisher Site | Google Scholar
G. Su, S. J. Cai, X. Gong, L. L. Wang, H. H. Li, and L. M. Wang, “Establishment of a blue light damage model of human retinal pigment epithelial cells in vitro,” Genetics and Molecular Research, vol. 15, no. 2, 2016.
View at: Publisher Site | Google Scholar
P. C. Meighan, C. Peng, and M. D. Varnum, “Inherited macular degeneration-associated mutations in CNGB3 increase the ligand sensitivity and spontaneous open probability of cone cyclic nucleotide-gated channels,” Frontiers in Physiology, vol. 6, p. 177, 2015.
View at: Publisher Site | Google Scholar
W. L. Wong, X. Su, X. Li et al., “Global prevalence of age-related macular degeneration and disease burden projection for 2020 and 2040: a systematic review and meta-analysis,” Lancet Global Health, vol. 2, no. 2, pp. e106–116, 2014.
View at: Publisher Site | Google Scholar
P. Ackland, “The accomplishments of the global initiative VISION 2020: the Right to Sight and the focus for the next 8 years of the campaign,” Indian Journal of Ophthalmology, vol. 60, no. 5, pp. 380–386, 2012.
View at: Publisher Site | Google Scholar
S. Nashine, P. Cohen, M. Chwa et al., “Humanin G (HNG) protects age-related macular degeneration (AMD) transmitochondrial ARPE-19 cybrids from mitochondrial and cellular damage,” Cell Death & Disease, vol. 8, no. 7, Article ID e2951, 2017.
View at: Publisher Site | Google Scholar
D. T. Organisciak and D. K. Vaughan, “Retinal light damage: mechanisms and protection,” Progress in Retinal and Eye Research, vol. 29, no. 2, pp. 113–134, 2010.
View at: Publisher Site | Google Scholar
K. Kaarniranta, D. Sinha, J. Blasiak et al., “Autophagy and heterophagy dysregulation leads to retinal pigment epithelium dysfunction and development of age-related macular degeneration,” Autophagy, vol. 9, no. 7, pp. 973–984, 2013.
View at: Publisher Site | Google Scholar
M. Sun, S. C. Finnemann, M. Febbraio et al., “Light-induced oxidation of photoreceptor outer segment phospholipids generates ligands for CD36-mediated phagocytosis by retinal pigment epithelium: a potential mechanism for modulating outer segment phagocytosis under oxidant stress conditions,” Journal of Biological Chemistry, vol. 281, no. 7, pp. 4222–4230, 2006.
View at: Publisher Site | Google Scholar
M. Valapala, C. Wilson, S. Hose et al., “Lysosomal-mediated waste clearance in retinal pigment epithelial cells is regulated by CRYBA1/βA3/A1-crystallin via V-ATPase-MTORC1 signaling,” Autophagy, vol. 10, no. 3, pp. 480–496, 2014.
View at: Publisher Site | Google Scholar
J. R. Sparrow, E. Gregory-Roberts, K. Yamamoto et al., “The bisretinoids of retinal pigment epithelium,” Progress in Retinal and Eye Research, vol. 31, no. 2, pp. 121–135, 2012.
View at: Publisher Site | Google Scholar
O. A. Anderson, A. Finkelstein, and D. T. Shima, “A2E induces IL-1ß production in retinal pigment epithelial cells via the NLRP3 inflammasome,” PLoS One, vol. 8, no. 6, Article ID e67263, 2013.
View at: Publisher Site | Google Scholar
J. R. Sparrow, J. Zhou, S. K. Ghosh, and Z. Liu, “Bisretinoid degradation and the ubiquitin-proteasome system,” Advances in Experimental Medicine & Biology, vol. 801, pp. 593–600, 2014.
View at: Publisher Site | Google Scholar
C. I. López Sanjurjo, S. C. Tovey, and C. W. Taylor, “Rapid recycling of Ca2+ between IP3-sensitive stores and lysosomes,” PLoS One, vol. 9, no. 10, Article ID e111275, 2014 Oct.
View at: Publisher Site | Google Scholar
C. Rosse, M. Linch, S. Kermorgant, A. J. M. Cameron, K. Boeckeler, and P. J. Parker, “PKC and the control of localized signal dynamics,” Nature Reviews Molecular Cell Biology, vol. 11, no. 2, pp. 103–112, 2010.
View at: Publisher Site | Google Scholar
P. Lipp and G. Reither, “Protein kinase C: the “masters” of calcium and lipid,” Cold Spring Harbor Perspectives in Biology, vol. 3, no. 7, Article ID a004556, 2011.
View at: Publisher Site | Google Scholar
T. Kawano, J. Inokuchi, M. Eto, M. Murata, and J. H. Kang, “Activators and inhibitors of protein kinase C (PKC): their applications in clinical trials,” Pharmaceutics, vol. 13, no. 11, p. 1748, 2021.
View at: Publisher Site | Google Scholar
F. Schutt, M. Bergmann, F. G. Holz, and J. Kopitz, “Isolation of intact lysosomes from human RPE cells and effects of A2-E on the integrity of the lysosomal and other cellular membranes,” Graefes Archive for Clinical and Experimental Ophthalmology, vol. 240, no. 12, pp. 983–988, 2002.
View at: Publisher Site | Google Scholar
S. Y. Jeong, X. Gu, and K. W. Jeong, “Photoactivation of N-retinylidene-N-retinylethanolamine compromises autophagy in retinal pigmented epithelial cells,” Food and Chemical Toxicology, vol. 131, Article ID 110555, 2019.
View at: Publisher Site | Google Scholar
E. Poliakov, N. V. Strunnikova, J. K. Jiang et al., “Multiple A2E treatments lead to melanization of rod outer segment-challenged ARPE-19 cells,” Molecular Vision, vol. 20, pp. 285–300, 2014.
View at: Google Scholar
M. Shigeto, C. Y. Cha, P. Rorsman, and K. Kaku, “A role of PLC/PKC-dependent pathway in GLP-1-stimulated insulin secretion,” Journal of Molecular Medicine (Berlin), vol. 95, no. 4, pp. 361–368, 2017.
View at: Publisher Site | Google Scholar
Y. Li, B. Chen, W. Zou et al., “The lysosomal membrane protein SCAV-3 maintains lysosome integrity and adult longevity,” Journal of Cell Biology, vol. 215, no. 2, pp. 167–185, 2016.
View at: Publisher Site | Google Scholar
H. Appelqvist, P. Waster, K. Kagedal, and K. Ollinger, “The lysosome: from waste bag to potential therapeutic target,” Journal of Molecular Cell Biology, vol. 5, no. 4, pp. 214–226, 2013.
View at: Publisher Site | Google Scholar
M. Chinappi, A. Via, P. Marcatili, and A. Tramontano, “On the mechanism of chloroquine resistance in Plasmodium falciparum,” PLoS One, vol. 5, no. 11, Article ID e14064, 2010.
View at: Publisher Site | Google Scholar
U. Repnik, M. Hafner Cesen, and B. Turk, “Lysosomal membrane permeabilization in cell death: concepts and challenges,” Mitochondrion, vol. 19, pp. 49–57, 2014.
View at: Publisher Site | Google Scholar
G. C. Baltazar, S. Guha, W. Lu et al., “Acidic nanoparticles are trafficked to lysosomes and restore an acidic lysosomal pH and degradative function to compromised ARPE-19 cells,” PLoS One, vol. 7, no. 12, Article ID e49635, 2012.
View at: Publisher Site | Google Scholar
P. M. Chen, Z. J. Gombart, and J. W. Chen, “Chloroquine treatment of ARPE-19 cells leads to lysosome dilation and intracellular lipid accumulation: possible implications of lysosomal dysfunction in macular degeneration,” Cell & Bioscience, vol. 1, no. 1, p. 10, 2011.
View at: Publisher Site | Google Scholar
R. Thome, S. C. P. Lopes, F. T. M. Costa, and L. Verinaud, “Chloroquine: modes of action of an undervalued drug,” Immunology Letters, vol. 153, no. 1, pp. 50–57, 2013.
View at: Publisher Site | Google Scholar
R. A. Radu, J. Hu, Q. Yuan et al., “Complement system dysregulation and inflammation in the retinal pigment epithelium of a mouse model for Stargardt macular degeneration,” Journal of Biological Chemistry, vol. 286, no. 21, pp. 18593–18601, 2011.
View at: Publisher Site | Google Scholar
M. Circu, J. Cardelli, M. Barr, K. O’Byrne, G. Mills, and H. El-Osta, “Modulating lysosomal function through lysosome membrane permeabilization or autophagy suppression restores sensitivity to cisplatin in refractory non-small-cell lung cancer cells,” PLoS One, vol. 12, no. 9, Article ID e0184922, 2017 Sep 25.
View at: Publisher Site | Google Scholar
E. Schrezenmeier and T. Dorner, “Mechanisms of action of hydroxychloroquine and chloroquine: implications for rheumatology,” Nature Reviews Rheumatology, vol. 16, no. 3, pp. 155–166, 2020.
View at: Publisher Site | Google Scholar

Copyright

Copyright © 2022 Maomei Luo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

PDF Download Citation

Download other formats

Order printed copies

Views

294

Downloads

395

Citations