Effects of white light on beta-catenin signaling pathway in retinal pigment epithelium

This study investigated the effect of visible light exposure on retinal pigment epithelium (RPE). The activation of Wnt/β-catenin pathway was investigated by immunofluorescence and Western blot analysis using human retinal pigment epithelial (ARPE-19) cells, which demonstrated that the exposure of white light induced the activation of the Wnt/β-catenin pathway. Real time RT-PCR demonstrated that the mRNA of α-smooth muscle actin (α-SMA), and vimentin increased 2.5-4-fold and that of zona occludens 1 (ZO-1) decreased approximately 0.8-fold after white light exposure. The up-regulation of vimentin expression and the down-regulation of ZO-1 were evident by Western blot analysis and immunohistochemistry. Moreover, the ability of phagocytosis of ARPE-19 cells decreased 0.6-fold after light exposure. Together, white light exposure was supposed to induce the activation of Wnt/β-catenin pathway, the changes in the expression markers of epithelial and mesenchymal cells in RPE cells, and the concomitant impairment of the ability of phagocytosis.     

Regulation of protein phosphorylation of the intermediate-sized filament vimentin in the ciliary epithelium of the mammalian eye

The intermediate-sized filaments of vimentin-type (Mr = 57,000) have been identified biochemically and immunochemically as a major cytoskeleton component in the ciliary epithelium of the mammalian eye. When human or rabbit ciliary processes, or cultured ciliary epithelial-derived cells were incubated in serum-free medium containing [32P]orthophosphate and any of the following agents: 1) beta-adrenergic agonists (isoproterenol or epinephrine), 2) direct activators of adenylate cyclase (cholera toxin or forskolin), 3) analogs of cyclic AMP (8-Br-cAMP), or 4) prostaglandin E1, the phosphorylation of vimentin was significantly enhanced. The maximal enhancement ranged, in vivo and in vitro, from about 3-fold in human to 5-fold in rabbit, with either 1 mM 8-Br-cAMP or 0.1 microM forskolin. Phosphorylation of vimentin increased in the presence of beta-adrenergic agonists and could be blocked by the antiglaucoma beta-adrenergic antagonist timolol. The alpha-adrenergic agonist phenylephrine had no effect on phosphorylation of vimentin. Indirect immunofluorescence microscopy using a monoclonal antibody, anti-vimentin, allowed the localization of vimentin filaments in cultured ciliary epithelial cells. Treatment of these cells in culture with the catecholamine hormone, isoproterenol (1 microM), resulted in a profound reorganization of vimentin filaments. This may be correlated with the enhanced levels of phosphorylated vimentin observed upon increasing cellular cyclic AMP.     

Differential FAK phosphorylation at Ser-910, Ser-843 and Tyr-397 induced by angiotensin II, LPA and EGF in intestinal epithelial cells

A rapid increase in the tyrosine phosphorylation of the non-receptor tyrosine kinase FAK is a prominent early event in fibroblasts stimulated by a variety of signaling molecules. However, a variety of epithelial cells, including intestinal epithelial cells, show a high basal level of tyrosine phosphorylated FAK that is only slightly further increased by addition of G protein-coupled receptor (GPCR) agonists or growth factors. In this study, we determined whether these stimuli could elicit FAK phosphorylation at serine residues, including Ser-910 and Ser-843. Our results show that multiple agonists including angiotensin II (ANGII), lysophosphatidic acid (LPA), phorbol esters and EGF induced a striking stimulation of FAK phosphorylation at Ser-910 in rat intestinal epithelial IEC-18 cells via an ERK-dependent pathway. In striking contrast, none of these stimuli promoted a significant further increase in FAK phosphorylation at Tyr-397 in these cells. These results were extended using cultures of polarized human colonic epithelial T84 cells. We found that either carbachol or EGF promoted a striking ERK-dependent phosphorylation of FAK at Ser-910, but these agonists caused only slight stimulation of FAK at Tyr-397 in T84 cells. In addition, we demonstrated that GPCR agonists also induced a dramatic increase of FAK phosphorylation at Ser-843 in either IEC-18 or T84 cells. Our results indicate that Ser-910 and Ser-843, rather than Tyr-397, are prominent sites differentially phosphorylated in response to neurotransmitters, bioactive lipids, tumor promoters and growth factors in intestinal epithelial cells.     

Isolation of plasma membranes from the bovine retinal pigment epithelium

Retinal pigment epithelium plasma membranes have been isolated by differential and density gradient centrifugation of glass-bead-bound, collagenase-treated cells. Electron microscopic evidence indicates that the glass-bead-bound cells were devoid of red blood cells, rod outer segments and other ocular cell contaminants. The plasma membranes were recovered in 4–6 μg/eye yields and purified 10-fold by 5′-nucleotidase and alkaline phosphodiesterase 1, and 6.5-fold by (Na⁺ + K⁺)-ATPase. Plasma membrane purity as measured by covalent labeling of the epithelial cell plasma membrane proteins with p-(diazonium) benzene[³²S]sulfonic acid was 8–19-fold. In purified plasma membranes contamination by mitochondria was undetectable and lysosomal contamination reduced 100-fold, while endoplasmic reticulum was 2-fold enriched. SDS-polyacrylamide gel electrophoresis of the plasma membrane proteins revealed 23–26 major bands by Coomassie blue staining and 12–16 major bands by radioactive labeling. The plasma membranes exhibited a 3-fold lower concentration of docosahexaenoic acid, a 3-fold higher cholesterol/phosphate ratio, and were 10-fold enriched in cholesterol per μg protein when compared to the whole cell fraction. Retinal epithelial plasma membranes contain an average of 1 mol cholesterol per mol of lipid phosphorus, a high palmitic acid concentration (39 mol%) and a low concentration of docosahexaenoic acid (2 mol%). The lipid profile of the retinal pigment epithelial plasma membranes indicates that they are typical of plasma membranes from many other cell types and that they appear to be less fluid than total rod outer segment membranes.     

Protective role of epithelium in the guinea pig airway

We developed an in vitro system to assess the role of the epithelium in regulating airway tone using the intact guinea pig trachea (J. Appl. Physiol. 64: 466-471, 1988). This method allows us to study the response of the airway when its inner epithelial surface or its outer serosal surface is stimulated independently. Using this system we evaluated how the presence of intact epithelium can affect pharmacological responsiveness. We first examined responses of tracheae with intact epithelium to histamine, acetylcholine, and hypertonic KCl when stimulated from the epithelial or serosal side. We then examined the effect of epithelial denudation on the responses to these agonists. With an intact epithelium, stimulation of the inner epithelial side always caused significantly smaller changes in diameter than stimulation of the outer serosal side. After mechanical denudation of the epithelium, these differences were almost completely abolished. In the absence of intact epithelium, the trachea was 35-fold more sensitive to histamine and 115-fold more sensitive to acetylcholine when these agents were applied to the inner epithelial side. In addition, the presence of an intact epithelium almost completely inhibited any response to epithelial side challenge with hypertonic KCl. These results indicate that the airway epithelial layer has a potent protective role in airway responses to luminal side stimuli, leading us to speculate that changes in airway reactivity measured in various conditions including asthma may result in part from changes in epithelial function.     

Comparative analysis of the uptake and expression of plasmid vectors in human ciliary and retinal pigment epithelial cells in vitro.

The retinal pigment epithelium is uniquely suited to gene therapy that uses lipid-mediated DNA transfer due to its high phagocytic activity in situ. We compared the relative efficacy of phagocytosis on the uptake of labeled plasmid vectors by retinal pigment epithelial and ciliary epithelial cells in vitro. Relative levels of endocytosis were then compared with the efficiency of marker transgene expression in these cells. Human retinal pigment epithelial and ciliary epithelial cells from a single donor were isolated and expanded in vitro. Polyplex-mediated transfections were performed using a rhodamine-labeled expression vector for green fluorescent protein. Rhodamine-labeled endosomes were examined by fluorescence microscopy at different time points. Rhodamine labeling and green fluorescent protein expression were analyzed by flow cytometry 48 h after transfection. These gene transfer studies showed that expression of transgenes does occur in both human retinal pigment epithelial and ciliary epithelial cells in vitro. Endocytosis of labeled plasmid vectors occurs at a significantly higher number and density in retinal pigment epithelial cells than in ciliary epithelial cells (P < 0.04). However, the efficiency of marker transgene expression is similar in the two cell types. These studies demonstrate that the higher intrinsic phagocytic activity does not enhance the efficacy of transgene expression in retinal pigment epithelial cells in vitro. Both human retinal pigment epithelial and ciliary epithelial cells are competent recipients for lipid-mediated gene transfer, and transgene expression occurs at similar levels in both cell types.     

Mouse retinal progenitor cell (RPC) cocultivation with retinal pigment epithelial cell culture affects features of RPC differentiation

We provide evidence that coculturing of retinal progenitor cells (RPC) with retinal pigment epithelial cells significantly biases the standard in vitro RPC differentiation patterns. In particular, in cocultivation experiments RPCs lost the ability to differentiate spontaneously and displayed approximately 2.1-2.4-fold increase in immunoreactivity to the neural stem cell marker nestin and approximately 1.6-1.7-fold increase in rod photoreceptor cell rhodopsin marker immunoreactivity. The data suggest the influence of the intercellular interaction networks on RPC differentiation.     

Ultrastructural study of the retinal pigment epithelium during metamorphosis in the sea lamprey (Petromyzon marinus L.)

Summary The sequence of morphological changes in the retinal pigment epithelium during the metamorphic period of the sea lamprey Petromyzon marinus L. has been investigated using electron microscopy. At early metamorphic stages (stages I and II), photoreceptors are present in a small zone of the retina. During these stages, the lateral surface of the epithelial cells shows zonulae occludentes and adhaerentes. The degree of cell differentiation varies throughout the retinal pigment epithelium. Cells covering the differentiated photoreceptors in the central retina have phagosomes, whereas pigment granules appear only in the retinal pigment epithelium dorsal to the optic nerve head. Most epithelial cells have myeloid bodies; their morphology is more complex around the optic nerve head. At stage III, when photoreceptors develop over the whole retina, the distribution of cytoplasmic organelles is almost homogeneous in the retinal pigment epithelium. Subsequently, the basal plasma membrane of the epithelial cells becomes progressively folded and their apical processes enlarged. In addition, extensive gap junctions develop between retinal pigment cells. In late metamorphic stages, noticeable growth of myeloid bodies occurs and consequently the retinal pigment epithelium resembles that of the adult. This study also describes, for the first time, the presence of wandering phagocytes in the retinal pigment epithelium of lampreys; their role in melanosome degradation is discussed.     

Human retinal pigment epithelial cells

''Human retinal pigment epithelial cells'' is the first set of guidelines on human retinal pigment epithelial cells in China, jointly drafted and agreed upon by experts from the Chinese Society for Stem Cell Research. This standard specifies technical requirements, test methods, inspection rules, instructions for usage, labelling requirements, packaging requirements, storage requirements and transportation requirements and waste disposal requirements for human retinal pigment epithelial cells, which is applicable to quality control during the process of manufacturing and testing of human retinal pigment epithelial cells. It was originally released by the Chinese Society for Cell Biology on 9 January 2021. We hope that publication of these guidelines will promote institutional establishment, acceptance and execution of proper protocols and accelerate the international standardization of human retinal pigment epithelial cells for applications.     

Inflammatory cytokines regulate microRNA-155 expression in human retinal pigment epithelial cells by activating JAK/STAT pathway

Inflammatory response of the retinal pigment epithelium plays a critical role in the pathogenesis of retinal degenerative diseases such as age-related macular degeneration. Our previous studies have shown that human retinal pigment epithelial (HRPE) cells, established from adult donor eyes, respond to inflammatory cytokines by enhancing the expression of a number of cytokines and chemokines. To investigate the role of microRNA (miRNA) in regulating this response, we performed microarray analysis of miRNA expression in HRPE cells exposed to inflammatory cytokine mix (IFN-γ + TNF-α + IL-1β). Microarray analysis revealed ∼11-fold increase in miR-155 expression, which was validated by real-time PCR analysis. The miR-155 expression was enhanced when the cells were treated individually with IFN-γ, TNF-α or IL-1β, but combinations of the cytokines exaggerated the effect. The increase in miR-155 expression by the inflammatory cytokines was associated with an increase in STAT1 activation as well as an increase in protein binding to putative STAT1 binding elements present in the MIR155 gene promoter region. All these activities were effectively blocked by JAK inhibitor 1. Our results show that the inflammatory cytokines increase miR-155 expression in human retinal pigment epithelial cells by activating the JAK/STAT signaling pathway.     

Acute change in the cyclic AMP content of rat mammary acini in vitro. Influence of physiological and pharmacological agents.

The cyclic AMP content of acini, freshly prepared from mammary tissue of lactating rats, was measured during incubation in vitro. Neither adrenergic agonists nor cyclic AMP phosphodiesterase inhibitors alone caused a change of more than 2-fold in the basal cyclic AMP content of acini. Together, however, these agents provoked increases of around 20-fold in acini cyclic AMP content. Forskolin caused similar effects. The relative potency of adrenergic agonists in increasing cyclic AMP in acini, together with the ability of selective antagonists to oppose such rises, indicated that beta 2-adrenergic receptors were involved in mediating the effects. Receptor-binding experiments using [3H]dihydroalprenolol and selective beta-antagonists confirmed the predominant presence of beta 2-adrenergic receptors on acini membranes and on membranes prepared from purified mammary secretory epithelial cells. These results elucidate some previous findings [Robson, Clegg & Zammit (1984) Biochem. J. 217, 743-749; Williamson, Munday, Jones, Roberts & Ramsey (1983) Adv. Enzyme Regul. 21, 135-145], questioning the role of cyclic AMP in the regulation of lipogenesis in mammary acini.     

Atrial natriuretic peptide binding, cross-linking, and stimulation of cyclic GMP accumulation and particulate guanylate cyclase activity in cultured cells

The stimulation of cyclic GMP accumulation and particulate guanylate cyclase activity by atrial natriuretic peptide (ANP) was compared to the affinity and number of ANP receptors in eight cultured cell types. At 100 nM, ANP increased cyclic GMP by 13-fold in bovine adrenal cortical, 35-fold in human lung fibroblast, 58-fold in canine kidney epithelial, 60-fold in bovine aortic smooth muscle, 120-fold in rat mammary epithelial, 260-fold in rat Leydig, 300-fold in bovine kidney epithelial, and 475-fold in bovine aortic endothelial cells. ANP (1 microM) increased particulate guanylate cyclase activity by 1.5-, 2.5-, 3.1-, 3.2-, 5.0-, 7.0-, 7.8-, and 8.0-fold in bovine adrenal cortical, bovine aortic smooth muscle, human lung fibroblast, canine kidney epithelial, rat mammary epithelial, rat Leydig, bovine kidney epithelial, and bovine aortic endothelial cells, respectively. Specific 125I-ANP binding to intact rat Leydig (3,000 sites/cell; Kd = 0.11 nM), bovine aortic endothelial (14,000 sites/cell; Kd = 0.09 nM), bovine adrenal cortical (50,000 sites/cell; Kd = 0.12 nM), human lung fibroblast (80,000 sites/cell; Kd = 0.32 nM), and bovine aortic smooth muscle (310,000 sites/cell; Kd = 0.82 nM) cells was saturable and high affinity. No specific and saturable ANP binding was detected in bovine and canine kidney epithelial and rat mammary epithelial cells. Two ANP-binding sites of 66,000 and 130,000 daltons were specifically labeled by 125I-ANP after cross-linking with disuccinimidyl suberate. The 130,000-dalton ANP-binding sites bound to a GTP-agarose affinity column, and the specific activity of guanylate cyclase was increased by 90-fold in this fraction. Our results demonstrate that the increase in cyclic GMP accumulation and particulate guanylate cyclase activity by ANP does not correlate with the affinity and number of ANP-binding sites. These results suggest that multiple populations of ANP receptors exist in these cells and that only one receptor subtype (130,000 daltons) is associated with particulate guanylate cyclase activity.     

Access to nectin favors herpes simplex virus infection at the apical surface of polarized human epithelial cells

Viral entry may preferentially occur at the apical or the basolateral surfaces of polarized cells, and differences may impact pathogenesis, preventative strategies, and successful implementation of viral vectors for gene therapy. The objective of these studies was to examine the polarity of herpes simplex virus (HSV) entry using several different human epithelial cell lines. Human uterine (ECC-1), colonic (CaCo-2), and retinal pigment (ARPE-19) epithelial cells were grown on collagen-coated inserts, and the polarity was monitored by measuring the transepithelial cell resistance. Controls were CaSki cells, a human cervical cell line that does not polarize in vitro. The polarized cells, but not CaSki cells, were 16- to 50-fold more susceptible to HSV infection at the apical surface than at the basolateral surface. Disruption of the tight junctions by treatment with EGTA overcame the restriction on basolateral infection but had no impact on apical infection. No differences in binding at the two surfaces were observed. Confocal microscopy demonstrated that nectin-1, the major coreceptor for HSV entry, sorted preferentially to the apical surface, overlapping with adherens and tight junction proteins. Transfection with small interfering RNA specific for nectin-1 resulted in a significant reduction in susceptibility to HSV at the apical surface but had little impact on basolateral infection. Infection from the apical but not the basolateral surface triggered focal adhesion kinase phosphorylation and led to nuclear transport of viral capsids and viral gene expression. These studies indicate that access to nectin-1 contributes to preferential apical infection of these human epithelial cells by HSV.     

SIRT3 deficiency increases mitochondrial oxidative stress and promotes migration of retinal pigment epithelial cells

Retinal pigment epithelial cells are closely associated with the pathogenesis of diabetic retinopathy. The mechanism by which diabetes impacts retinal pigment epithelial cell function is of significant interest. Sirtuins are an important class of proteins that primarily possess nicotinamide adenine dinucleotide-dependent deacetylases activity and involved in various cellular physiological and pathological processes. Here, we aimed to examine the role of sirtuins in the induction of diabetes-associated retinal pigment epithelial cell dysfunction. High glucose and platelet-derived growth factor (PDGF) treatment induced epithelial–mesenchymal transition and the migration of retinal pigment epithelial cells, and decreased sirtuin-3 expression. Sirtuin-3 knockdown using siRNA increased epithelial–mesenchymal transition and migration of retinal pigment epithelial cells. In contrast, sirtuin-3 overexpression attenuated the effects caused by high glucose and PDGF on epithelial–mesenchymal transition and migration of retinal pigment epithelial cells, suggesting that sirtuin-3 deficiency contributed to retinal pigment epithelial cell dysfunction induced by high glucose and PDGF. Mechanistically, sirtuin-3 deficiency induced retinal pigment epithelial cell dysfunction by the overproduction of mitochondrial reactive oxygen species. These results suggest that sirtuin-3 deficiency mediates the migration of retinal pigment epithelial cells, at least partially by increasing mitochondrial oxidative stress, and shed light on the importance of sirtuin-3 and mitochondrial reactive oxygen species as potential targets in diabetic retinopathy therapy.     

Metabolism of P2 receptor agonists in human airways: implications for mucociliary clearance and cystic fibrosis

Extracellular nucleotides are among the most potent mediators of mucociliary clearance (MCC) in human lungs. However, clinical trials revealed that aerosolized nucleotides provide only a transient improvement of MCC to patients diagnosed with cystic fibrosis (CF). In this study, we identified the mechanism that eliminates extracellular nucleotides from human airways. Polarized primary cultures of human bronchial epithelial cells were impermeable to extracellular nucleotides but rapidly dephosphorylated ATP into ADP, AMP, and adenosine. The half-life of a therapeutic ATP concentration (0.1 mm) was approximately 20 s within the periciliary liquid layer. The mucosal epithelial surface eliminated P2 receptor agonists (ATP = UTP > ADP > UDP) at 3-fold higher rates than the serosal surface. We also showed that mucosal (not serosal) ectoATPase activity increases toward areas most susceptible to airway obstruction (nose < bronchi < bronchioles). Bronchial cultures from patients with CF, primary ciliary dyskinesia, or alpha1-antitrypsin deficiency exhibited 3-fold higher mucosal (not serosal) ectoATPase activity than normal cultures. Time course experiments indicated that CF enhances ATP elimination and adenosine accumulation on the mucosal surface. Furthermore, nonspecific alkaline phosphatase was identified as the major regulator of airway nucleotide concentrations in CF, primary ciliary dyskinesia, and alpha1-antitrypsin deficiency. The ectoAT-Pase activity and mRNA expression of mucosally restricted nonspecific alkaline phosphatase were 3-fold higher on bronchial cultures from these patients than from healthy subjects. This study demonstrates that the duration of nucleotide-mediated MCC is limited by epithelial ectonucleotidases throughout human airways, with the efficiency of this mechanism enhanced in chronic inflammatory lung diseases, including CF.     

Retinal pigment epithelial cell proliferation

The human retinal pigment epithelium forms early in development and subsequently remains dormant, undergoing minimal proliferation throughout normal life. Retinal pigment epithelium proliferation, however, can be activated in disease states or by removing retinal pigment epithelial cells into culture. We review the conditions that control retinal pigment epithelial proliferation in culture, in animal models and in human disease and interpret retinal pigment epithelium proliferation in context of the recently discovered retinal pigment epithelium stem cell that is responsible for most in vitro retinal pigment epithelial proliferation. Retinal pigment epithelial proliferation-mediated wound repair that occurs in selected macular diseases is contrasted with retinal pigment epithelial proliferation-mediated fibroblastic scar formation that underlies proliferative vitreoretinopathy. We discuss the role of retinal pigment epithelial proliferation in age-related macular degeneration which is reparative in some cases and destructive in others. Macular retinal pigment epithelium wound repair and regression of choroidal neovascularization are more pronounced in younger than older patients. We discuss the possibility that the limited retinal pigment epithelial proliferation and latent wound repair in older age-related macular degeneration patients can be stimulated to promote disease regression in age-related macular degeneration.     

Elimination of egg pigment from developing ocular tissues in the frog Rana pipiens

The method by which egg pigment is eliminated from the developing retina, corneal epithelium and lens in Rana pipiens was studied with light and electron microscopy. The retina expells egg pigment into the space between the retina and pigment epithelium. This pigment is then engulfed by the pigment epithelial cells. The corneal epithelium eliminates egg pigment directly to the outside via the free surface of the epithelial cells. Egg pigment accumulates in a few cells in the lens. These cells probably degenerate and are extruded. These ectodermal derivatives in the eye are free of egg pigment long before ectodermal derivatives in other parts of the embryo lose their pigment. The early elimination of egg pigment from ocular tissues may related to the fact that these tissues must be transparent in order that light may pass freely to the photoreceptors.     

Synergistic effects of pravastatin and pioglitazone in renal tubular epithelial cells induced by transforming growth factor-beta1

Recent studies suggest that treatment with PPAR-gamma agonists and statins have beneficial effects on renal disease. However, the combined effects of PPAR-gamma agonists and statins in human renal epithelial cells are unknown. Our present study revealed that there were synergistic effects of pravastatin and pioglitazone in the expression of alpha-smooth muscle actin (alpha-SMA), connective tissue growth factor (CTGF), fibronectin (FN), plasminogen activator inhibitor-1 (PAI-1) and collagen 1 in human renal proximal tubular epithelial cells induced by transforming growth factor-beta 1 (TGF-beta1). The beneficial effects of combined therapy against renal tubular epithelial cell injury are attributed, at least in part, to the inhibition of transdifferentiation, extracellular matrix deposition and cytokine production.     

PAR-2 activation and LPS synergistically enhance inflammatory signaling in airway epithelial cells by raising PAR expression level and interleukin-8 release

Protease-activated receptors (PARs) are involved in the contribution of airway epithelial cells to the development of inflammation by release of pro- and anti-inflammatory mediators. Here, we evaluated in epithelial cells the influence of LPS and continuous PAR activation on PAR expression level and the release of the proinflammatory chemokine IL-8. We studied primary human small airway epithelial cells and two airway epithelial cell lines, A549 and HBE cells. LPS specifically upregulated expression of PAR-2 but not of PAR-1. Exposure of epithelial cells to PAR-1 or PAR-2 agonists increased the PAR-1 expression level. The PAR-2 agonist exhibited higher potency than PAR-1 activators. However, the combined exposure of epithelial cells to LPS and PAR agonists abrogated the PAR-1 upregulation. The PAR-2 expression level was also upregulated after exposure to PAR-1 or PAR-2 agonists. This elevation was higher than the effect of PAR agonists on the PAR-1 level. In contrast to the PAR-1 level, the PAR-2 level remained elevated under concomitant stimulation with LPS and PAR-2 agonist. Furthermore, activation of PAR-2, but not of PAR-1, caused production of IL-8 from the epithelial cells. Interestingly, both in the epithelial cell line and in primary epithelial cells, there was a potentiation of the stimulation of the IL-8 synthesis and release by PAR-2 agonist together with LPS. In summary, these results underline the important role of PAR-2 in human lung epithelial cells. Moreover, our study shows an intricate interplay between LPS and PAR agonists in affecting PAR regulation and IL-8 production.