Prostaglandin E receptor subtype EP3 in conjunctival epithelium regulates late-phase reaction of experimental allergic conjunctivitis

Acetylsalicylic acid aggravates anaphylaxis in a PGE2-dependent manner

Acetylsalicylic acid (ASA) can exert proanaphylactic effects, but the extent of this phenomenon and its underlying mechanisms are undefined. Yet, low homeostatic prostaglandin E2 (PGE2) levels have been associated with anaphylaxis. In this study, we investigated whether the proanaphylactic effect of ASA is PGE2 dependent. We assessed the effect of ASA in experimental anaphylaxis models, analyzed a large dataset of patients with anaphylaxis, and performed titrated allergen challenges in ASA-treated allergic individuals. Registry data indicated an increased risk for severe anaphylaxis in patients with ASA comedication. ASA pretreatment aggravated allergen-dependent anaphylaxis in mice, whereas histamine-induced anaphylaxis remained unaffected. Exacerbation was due to reduced PGE2, as its stabilization or the use of prostanoid E receptor (EP) agonists reversed the proanaphylactic effects of ASA. EP2-, EP3-, and EP4 receptor-deficient mice revealed that each receptor individually contributed to ASA susceptibility. In patients with allergy, prior ASA intake increased skin responsiveness to allergen but not to histamine. Conversely, the responses of basophils to ex vivo FcεRI aggregation remained unaltered, indicating that ASA operated by enhancing the stimulability of mast cells in a PGE2-dependent manner. Collectively, our data reveal a central role of the PGE2 network in ASA-aggravated anaphylaxis. EP receptors could be potential targets to prevent or alter the outcome of anaphylaxis.

Regulation of innate immune response by miRNAs up-regulated in Stevens-Johnson syndrome with severe ocular complications

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe mucocutaneous disorders characterized by extensive tissue necrosis; they are often accompanied by severe ocular complications (SOC). The regulatory role of microRNAs (miRNAs) in modulating immune responses in SJS/TEN is not fully understood, particularly in relation to chronic SOC. We explored the expression profiles of specific miRNAs and their potential impact on the regulation of key innate immune genes in patients with SJS/TEN with SOC. We analyzed plasma samples from 100 patients with chronic stage SJS/TEN with SOC and 92 healthy controls to examine the expression levels of eight specific miRNAs (let-7a-5p, let-7d-3p, let-7e-5p, miR-146a-5p, miR-130a-3p, miR-151a-3p, miR-151a-5p, miR-27b-3p) using quantitative RT-PCR (RT-qPCR). In addition, we subjected mononuclear cells from 12 SJS/TEN patients and 9 controls to RT-qPCR to assess the expression of the innate immune-related genes IFI44L, TNFSF10, AIM2, RSAD2, CXCL10, TRIM22, IFI27, and IFIT2. Significant upregulation of 4 miRNAs (let-7a-5p, let-7e-5p, miR-146a-5p, and miR-27b-3p) was observed in the plasma of SJS/TEN patients; this correlated with the increased expression of TLR3, RIG-I, and MDA5. Furthermore, MDA5, IFI44L, RSAD2, CXCL10, and IFIT2 were also significantly up-regulated in the mononuclear cells from these patients, indicating a systemic modulation of immune response genes. Our findings demonstrate that specific miRNAs are up-regulated in SJS/TEN with SOC and associated with the upregulation of critical immune response genes, suggesting their involvement in the pathogenesis and persistence of SOC. These miRNAs and their target genes may serve as potential biomarkers or therapeutic targets in managing SJS/TEN with SOC.

Severe cutaneous adverse reactions

Severe cutaneous adverse reactions (SCARs), which include Stevens-Johnson syndrome and toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (also known as drug-induced hypersensitivity syndrome), acute generalized exanthematous pustulosis, and generalized bullous fixed drug eruption, are life-threatening conditions. The pathogenesis of SCARs involves T cell receptors recognizing drug antigens presented by human leukocyte antigens, triggering the activation of distinct T cell subsets. These cells interact with keratinocytes and various immune cells, orchestrating cutaneous lesions and systemic manifestations. Genetic predisposition, impaired drug metabolism, viral reactivation or infections, and heterologous immunity influence SCAR development and clinical presentation. Specific genetic associations with distinct SCAR phenotypes have been identified, leading to the implementation of genetic screening before prescription in various countries to prevent SCARs. Whilst systemic corticosteroids and conventional immunomodulators have been the primary therapeutic agents, evolving strategies, including biologics and small molecules targeting tumour necrosis factor, different cytokines, or Janus kinase signalling pathways, signify a shift towards a precision management paradigm that considers individual clinical presentations.

Prostaglandin EP3 receptor activation is antinociceptive in sensory neurons via PI3Kγ, AMPK and GRK2

BACKGROUND AND PURPOSE

Prostaglandin E₂ is considered a major mediator of inflammatory pain, by acting on neuronal G_s protein-coupled EP2 and EP4 receptors. However, the neuronal EP3 receptor, colocalized with EP2 and EP4 receptor, is G_i protein-coupled and antagonizes the pronociceptive prostaglandin E₂ effect. Here, we investigated the cellular signalling mechanisms by which the EP3 receptor reduces EP2 and EP4 receptor-evoked pronociceptive effects in sensory neurons.

EXPERIMENTAL APPROACH

Experiments were performed on isolated and cultured dorsal root ganglion (DRG) neurons from wild type, phosphoinositide 3-kinase γ (PI3Kγ)^-/- , and PI3Kγ^{kinase dead (KD)/KD} mice. For subtype-specific stimulations, we used specific EP2, EP3, and EP4 receptor agonists from ONO Pharmaceuticals. As a functional readout, we recorded TTX-resistant sodium currents in patch-clamp experiments. Western blots were used to investigate the activation of intracellular signalling pathways. EP4 receptor internalization was measured using immunocytochemistry.

KEY RESULTS

Different pathways mediate the inhibition of EP2 and EP4 receptor-dependent pronociceptive effects by EP3 receptor stimulation. Inhibition of EP2 receptor-evoked pronociceptive effect critically depends on the kinase-independent function of the signalling protein PI3Kγ, and adenosine monophosphate activated protein kinase (AMPK) is involved. By contrast, inhibition of EP4 receptor-evoked pronociceptive effect is independent on PI3Kγ and mediated through activation of G protein-coupled receptor kinase 2 (GRK2), which enhances the internalization of the EP4 receptor after ligand binding.

CONCLUSION AND IMPLICATIONS

Activation of neuronal PI3Kγ, AMPK, and GRK2 by EP3 receptor activation limits cAMP-dependent pain generation by prostaglandin E₂ . These new insights hold the potential for a novel approach in pain therapy.

Susceptibility Genes and HLA for Cold Medicine-Related SJS/TEN with SOC

We investigated the genetic predisposition for the pathogenesis of Stevens–Johnson syndrome/epidermal necrolysis with severe ocular complications (SJS/TEN with SOC). Cold medicines (CMs) including multi-ingredient cold-medications and non-steroidal anti-inflammatory drugs (NSAIDs) were implicated in the development of SJS/TEN with SOC. Studies on the association between HLA genotypes and CM-related SJS/TEN with SOC (CM-SJS/TEN with SOC) revealed an association with HLA-A*02:06 in the Japanese; it may be a marker in Koreans. HLA-B*44:03 was associated with the Japanese, Thais, and Indians; in Brazilians of European ancestry, it may be a positive marker. PTGER3 is a susceptibility gene; HLA-A*02:06 and PTGER3 polymorphisms exerted additive effects in Japanese and Korean patients. A genome-wide association study showed that IKZF1 was associated with the Japanese. A meta-analysis including Japanese, Koreans, Indians, and Brazilians also revealed an association between CM-SJS/TEN with SOC and IKZF1. The upregulation of hsa-miR-628-3p in the plasma of SJS/TEN with SOC patients may suppress the expression of TLR3 and innate immune-related genes. Not only CMs but also the interaction of TLR3, PTGER3, IKZF1, and HLA and maybe some microbial infections are necessary for the onset of SJS/TEN with SOC.

Silicone hydrogel contact lenses retain and document ocular surface lipid mediator profiles

CLINICAL RELEVANCE

A leading reason for patients to abandon their contact lenses is discomfort. Mechanisms and biomarkers for lens discomfort remain to be elucidated.

BACKGROUND

Physical stress and tear film interaction are likely factors for lens discomfort. Lipid mediators are generated from polyunsaturated fatty acids. They regulate ocular surface physiology and pathophysiology, are constituents of human tears and may interact with contact lenses. This study set out to determine if hydrogel lenses and silicone hydrogel lenses interact with tear film polyunsaturated fatty acids and polyunsaturated fatty acids-derived mediators.

METHODS

In vitro incubations, rat experiments and analysis of worn human lenses assessed polyunsaturated fatty acids and lipid mediator interactions with lenses. Silicone hydrogel and hydrogel lenses were incubated with lipid mediators and polyunsaturated fatty acids up to 24 hours. Rats were fitted with custom silicone hydrogel lenses and basal tears collected. Silicone hydrogel lenses worn for 2 weeks were obtained from 57 human subjects. Tear and lens lipidomes were quantified by mass spectrometry.

RESULTS

Silicone hydrogel lenses retained polyunsaturated fatty acids and lipid mediators within 15 minutes in vitro. Lenses contained 90% of total polyunsaturated fatty acids and 83-89% of total monohydroxy fatty acids by 12 hours. Retention correlated with polarity of lipid mediators and lipophilic properties of silicone hydrogel lenses. Polyunsaturated fatty acids and lipid mediators such as lipoxygenase- and cyclooxygenase-derived eicosanoids were present in tears and worn lenses from rats. Worn silicone hydrogel lenses from human subjects established robust and lens-type specific lipidomes with high levels of polyunsaturated fatty acids, lipoxygenase-pathway markers and subject-specific differences in lipoxin A₄ and leukotriene B₄.

CONCLUSION

Worn silicone hydrogel lenses rapidly retain and accumulate tear polyunsaturated fatty acids and lipid mediators. Marked subject and lens type differences in the lipidome may document changes in ocular surface physiology, cell activation or infection that are associated with lens wear. If contact lens discomfort and adverse events induce specific tear and lens fatty acid and lipid mediator profiles warrants further studies.

Findings by an International Collaboration on SJS/TEN With Severe Ocular Complications

Stevens-Johnson Syndrome (SJS) is an acute inflammatory vesiculobullous reaction of the skin and mucosa, e.g., the ocular surface, oral cavity, and genitals. In patients with extensive skin detachment and a poor prognosis, the condition is called toxic epidermal necrolysis (TEN). Not all, but some patients with SJS/TEN manifest severe ocular lesions. Approximately 50% of SJS/TEN patients diagnosed by dermatologists and in burn units suffer from severe ocular complications (SOC) such as severe conjunctivitis with pseudomembrane and ocular surface epithelial defects in the acute stage. In the chronic stage, this results in sequelae such as severe dry eye and visual disturbance. Before 2005, our group of Japanese scientists started focusing on ophthalmic SJS/TEN with SOC. We found that cold medicines were the main causative drugs of SJS/TEN with SOC and that in Japanese patients, HLA-A ^* 02:06 and HLA-B ^* 44:03 were significantly associated with cold medicine-related SJS/TEN with SOC (CM-SJS/TEN with SOC). We expanded our studies and joined scientists from Korea, Brazil, India, Taiwan, Thailand, and the United Kingdom in an international collaboration to detect the genetic predisposition for SJS/TEN with SOC. This collaboration suggested that in Japanese patients, cold medicines, including NSAIDs, were the main causative drugs, and that HLA-A ^* 02:06 was implicated in Japanese and Korean patients and HLA-B ^* 44:03 in Japanese-, Indian-, and European ancestry Brazilian patients. Our joint findings reveal that there are ethnic differences in the HLA types associated with SJS/TEN with SOC.

Pathogenesis of Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis With Severe Ocular Complications

Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) is an acute inflammatory vesiculobullous reaction of the mucosa of the ocular surface, oral cavity, and genitals, and of the skin. Severe ocular complications (SOC) are observed in about half of SJS/TEN patients diagnosed by dermatologists and in burn units. Ophthalmologists treat SOC, and they tend to encounter the patients not only in the acute stage, but also in the chronic stage. Our investigation of the pathogenesis of SJS/TEN with SOC led us to suspect that abnormal innate mucosal immunity contributes to the ocular surface inflammation seen in SJS/TEN with SOC. We confirmed that cold medicines such as NSAIDs and multi-ingredient cold medications are the main causative drugs for SJS/TEN with SOC. Single nucleotide polymorphism (SNP) association analysis of cold medicine-related SJS/TEN with SOC showed that the Toll-like receptor 3 (TLR3)-, the prostaglandin-E receptor 3 (PTGER3)-, and the IKZF1 gene were significantly associated with SNPs and that these genes could regulate mucocutaneous inflammation including that of the ocular surface. We also examined the tear cytokines of SJS/TEN with SOC in the chronic stage and found that IL-8, IL-6, IFN-γ, RANTES, eotaxin, and MIP-1β were significantly upregulated in SJS/TEN with SOC in the chronic stage. Only IP-10 was significantly downregulated in SJS/TEN with SOC in the chronic stage. This mini-review summarizes the pathological mechanisms that we identified as underlying the development of SJS/TEN with SOC.

Regulation of gene expression by miRNA-455-3p, upregulated in the conjunctival epithelium of patients with Stevens-Johnson syndrome in the chronic stage

To investigate the role of miRNA in the pathogenesis underlying ocular surface complications in patients with Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) in the chronic stage. Using oligonucleotide microarrays, we performed comprehensive miRNA analysis of the conjunctival epithelium of SJS/TEN patients with severe ocular complications (SOC) in the chronic stage (n = 3). Conjunctival epithelium of patients with conjunctival chalasis (n = 3) served as the control. We confirmed the down- and up-regulation of miRNA of interest by quantitative real-time polymerase chain reaction (RT-PCR) assays using the conjunctival epithelium from 6 SJS/TEN with SOC patients and 7 controls. We focused on miRNA-455-3p, which is significantly upregulated in the conjunctival epithelium of the SJS/TEN patients, and investigated its function by inhibiting miR-455-3p in primary human conjunctival epithelial cells (PHCjEs). Comprehensive miRNA expression analysis showed that the expression of 5 kinds of miRNA was up-regulated more than fivefold, and that the expression of another 5 kinds of miRNA was down-regulated by less than one-fifth. There was a significant difference between the SJS/TEN patients and the controls [analysis of variance (ANOVA) p < 0.05]. Quantitative miRNA PCR assay showed that hsa-miR-31* and hsa-miR-455-3p were significantly up-regulated in the conjunctival epithelium of the SJS/TEN patients. Comprehensive gene expression analysis of PHCjEs transfected with the hsa-miR-455-3p inhibitor and quantitative RT PCR assay showed that ANKRD1, CXCL8, CXCL2, GEM, PTGS2, RNASE8, IL6, and CXCL1 were down-regulated by the hsa-miR-455-3p inhibitor. Quantitative RT-PCR, focused on the genes that tended to be up-regulated in SJS/TEN with SOC, revealed that the expression of IL1A, KPRP, IL36G, PPP1R3C, and ADM was significantly down-regulated in PHCjEs transfected with the hsa-miR-455-3p inhibitor. Our results suggest that miRNA-455-3p could regulate many genes including innate immune related genes in human conjunctival epithelium, and that its up-regulation contributes to the pathogenesis on the ocular surface in SJS/TEN patients with the SOC in the chronic stage. Our findings may lead to the development of new treatments using the miRNA-455-3p inhibitor.

HLA genotypes and cold medicine-induced Stevens-Johnson syndrome/toxic epidermal necrolysis with severe ocular complications: a systematic review and meta-analysis

Serious cutaneous adverse drug reactions [i.e., SJS/TEN with severe ocular complications (SOC)] associated with cold medicine (CM) were reported in several studies. To assess the risks of CM-induced SJS/TEN with SOC, systematic review and meta-analysis were employed. Studies investigating associations between HLA genotypes and CM-induced SJS/TEN with SOC were systematically searched in PubMed, Scopus and the Cochrane Library. Overall odds ratios (ORs) with 95% CIs were calculated using a random-effects model to determine these associations. An initial search of the databases identified 24,011 articles, of which 6 studies met the inclusion criteria. In total from all studies, associations between 81 different HLA genotypes and CM-induced SJS/TEN with SOC (i.e., 22 different HLA-A genotypes, 40 different HLA-B genotypes and 19 different HLA-C genotypes) were investigated. Risk factors to develop SJS/TEN with SOC in patients who used CM were identified from our meta-analysis. HLA-A*0206 (OR = 3.90; 95% CI = 1.96–7.77), HLA-A*3303 (OR = 2.28; 95% CI = 1.31–3.97), HLA-B*4403 (OR = 3.27; 95% CI = 1.52–7.03) and HLA-C*0501 (OR = 2.55; 95% CI = 1.19–5.44) were associated with CM-induced SJS/TEN with SOC. With our results demonstrating a significant association between using of CMs and the severe ADR, a genetic testing can be helpful. However, the CMs are commonly used as an over-the-counter drug in practically almost of people in populations worldwide, the genetic screening prior to use of the CMs might not be cost-effective. Nonetheless, for people with a family history of developing the ADRs with a possible involvement of CMs, a genetic screening may be beneficial.

Stevens-Johnson syndrome/toxic epidermal necrolysis with severe ocular complications

Introduction: Stevens-Johnson syndrome (SJS) and its severe phenotype, toxic epidermal necrolysis (TEN), are acute inflammatory vesiculobullous reactions of the skin and mucosa. Approximately 50% of SJS/TEN patients diagnosed by dermatologists and in burn units suffer from severe ocular complications (SOC) in the acute stage.Areas covered: Earlier studies on patients with SJS/TEN with SOC identified cold medicines including multi-ingredient cold medications and non-steroidal anti-inflammatory drugs as the main eliciting drugs. HLA analyzes showed that genetic predisposition might play a role in the response to these drugs. Our analysis of the association between HLA genotypes and cold medicine-related SJS/TEN (CM-SJS/TEN) with SOC revealed that certain HLA genotypes play a role in the development of SJS/TEN with SOC. Genetic predisposition and other factors contributing to the elicitation of CM-SJS/TEN with SOC and the management of patients in the acute and chronic stage of the disease are discussed.Expert opinion: The main sequelae of SJS/TEN are ocular sequelae with visual disturbance. SJS/TEN with SOC needs ophthalmic treatment in addition to systemic treatment from the onset time to reduce the ophthalmic sequelae. In addition, HLA examination and public awareness of SJS/TEN with SOC due to cold medicine use might contribute to preventing visual disturbance due to SJS/TEN.Abbreviations: SJS: Stevens-Johnson syndrome; TEN: toxic epidermal necrolysis; SOC: severe ocular complications.

Association of HLA class I and II gene polymorphisms with acetaminophen-related Stevens-Johnson syndrome with severe ocular complications in Japanese individuals

Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are acute-onset mucocutaneous diseases induced by infectious agents and/or inciting drugs. We have reported that the main causative drugs for SJS/TEN with severe ocular complications (SOC) were cold medicines, including multi-ingredient cold medications and nonsteroidal anti-inflammatory drugs (NSAIDs). Moreover, we also reported that acetaminophen is the most frequent causative drug in various cold medicines. In this study, we focused on acetaminophen-related SJS/TEN with SOC and analyzed HLA-class II (HLA-DRB1, DQB1) in addition to HLA-class I (HLA-A, B, C). We studied the histocompatibility antigen genes HLA-DRB1 and DQB1 in addition to HLA-A, B, and C in 80 Japanese patients with acetaminophen-related SJS/TEN with SOC. We performed polymerase chain reaction amplification followed by hybridization with sequence-specific oligonucleotide probes (PCR-SSO) using commercial bead-based typing kits. We also used genotyped data from 113 healthy volunteers for HLA-DRB1 and DQB1, and 639 healthy volunteers for HLA-A, B, and C. HLA-DRB1*08:03 and DRB1*12:02 were associated with acetaminophen-related SJS/TEN with SOC, although the results ceased to be significant when we corrected the p-value for the number of alleles detected. HLA-A*02:06 was strongly associated with acetaminophen-related SJS/TEN with SOC (carrier frequency: p = 4.7 × 10⁻¹², Pc = 6.6 × 10⁻¹¹, OR = 6.0; gene frequency: p = 8.0 × 10⁻¹³, Pc = 1.1 × 10⁻¹¹, OR = 4.9). HLA-B*13:01 (carrier frequency: p = 2.0 × 10⁻³, Pc = 0.042, OR = 4.1; gene frequency: p = 2.2 × 10⁻³, Pc = 0.047, OR = 3.9), HLA-B*44:03 (carrier frequency: p = 2.1 × 10⁻³, Pc = 0.045, OR = 2.4) and HLA-C*14:03 (carrier frequency: p = 3.4 × 10⁻³, Pc = 0.045, OR = 2.3) were also significantly associated, while HLA-A*24:02 was inversely associated (gene frequency: p = 6.3 × 10⁻⁴, Pc = 8.8 × 10⁻³, OR = 0.5). Acetaminophen-related SJS/TEN with SOC was not associated with HLA-class II (HLA-DRB1, DQB1). However, for acetaminophen-related SJS/TEN with SOC, we found an association with HLA-B*13:01 and HLA- C*14:03 in addition to HLA-A*02:06 and HLA-B*44:03, which have been described previously.

Researchers have identified two new gene variants that could predispose to a rare drug reaction to a common cold drug. Stevens–Johnson syndrome can be triggered by drugs and infections and is characterized by blistering of the skin and mucous membranes. Mayumi Ueta of Kyoto Prefectural University of Medicine in Japan and colleagues found an association between variants in two genes coding for human leukocyte antigen (HLA) class I molecules and Stevens–Johnson syndrome induced by acetominophen and complicated by severe eye ulcerations in Japanese patients. HLA genes code for cell surface proteins that help the immune system distinguish normal from foreign cells. Other studies have identified population-specific HLA variants associated with the syndrome. This study provides further evidence of HLA-specific ethnic differences in people diagnosed with the condition.

The roles of omega-3 fatty acids and resolvins in allergic conjunctivitis

PURPOSE OF REVIEW

Lipids are one of the most important constituents in our body. Advances of lipidomics are elucidating the new roles of various lipid molecules in allergic diseases. For example, some reports showed anti-inflammatory effects of omega-3 fatty acids (FAs), such as docosahexaenoic acid, eicosapentaenoic acid, and their metabolites, on allergic diseases. Here, we introduce the role of lipid mediators in allergic conjunctivitis mouse model.

RECENT FINDINGS

Lipidomics using liquid chromatography-tandem mass spectrometry can profile numerous lipid molecules from small tissue samples such as conjunctival specimens. Lipidomics analysis showed that various inflammatory lipid mediators are produced in the conjunctival tissue of allergic conjunctivitis mouse model. Dietary omega-3 FAs reduced these inflammatory lipid mediators in the conjunctiva and alleviated allergic conjunctivitis symptoms in mouse models. In addition, the roles of specialized proresolving lipid mediators (SPMs) have been reported for allergic inflammation.

SUMMARY

Lipid mediators have important roles for the pathophysiology of the allergic diseases including allergic conjunctivitis. Omega-3 FAs and SPMs are expected as new treatment tools for allergic conjunctivitis.

Expression of prostaglandin E2 receptor 3 in the eyelid epidermis of patients with Stevens-Johnson syndrome/toxic epidermal necrolysis

Background/aims

In a previous genome-wide association study of Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN) patients we reported the association between SJS/TEN and the prostaglandin E receptor 3 (PTGER3) gene, and that its protein PGE2 receptor 3 (EP3) was markedly downregulated in the conjunctival epithelium of SJS/TEN patients. Here we examined EP3 expression of the eyelid epidermis in SJS/TEN patients with severe ocular complications and investigated the function of EP3.

Methods

For the immunohistochemical study, we obtained eyelid samples from five SJS/TEN patients and five patients without SJS/TEN (control subjects) who were undergoing surgery to treat trichiasis, and investigated the expression of EP3 protein in the epidermis of those samples. To investigate the EP3 function in the human epidermal keratinocytes, we performed ELISA and quantitative reverse transcription polymerase chain reaction, since it is reported that PGE2 suppresses cytokine production via EP3 in human conjunctival epithelium.

Results

The results of the immunohistochemical study revealed that EP3 expression in the eyelid epidermis of the SJS/TEN patients was the same as that in the controls. PGE2 and a selective EP3 agonist suppressed cytokine production and expression induced by polyinosine-polycytidylic acid stimulation, such as chemokine ligand 5 and chemokine motif ligand 10.

Conclusion

Our findings revealed that in chronic-phase SJS/TEN, EP3 protein was expressed in the eyelid epidermis and was not downregulated, unlike in conjunctival epithelium, and that PGE2 could suppress cytokine production via EP3 in human epidermal keratinocytes. Thus, EP3 expression in the epidermis might contribute to a silencing of skin inflammation in chronic-phase SJS/TEN.

Association of human antigen class I genes with cold medicine-related Stevens-Johnson syndrome with severe ocular complications in a Korean population

BACKGROUND/AIMS

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are a spectrum of diseases that cause an acute vesiculobullous reaction in the skin and mucous membranes. The occurrence of these diseases is associated with various drugs, a large proportion of which is comprised cold medicines (CM). We try to investigate the association between human leucocyte antigen (HLA) class I genes and CM-related SJS/TEN (CM-SJS/TEN) with severe ocular complications (SOC) in the Korean population.

METHODS

This multicentre case-control study enrolled 40 Korean patients with CM-SJS/TEN with SOC and 120 age-matched and sex-matched Korean healthy volunteers between January 2012 and May 2014. HLA genotyping was performed using PCR followed by hybridisation with sequence-specific oligonucleotide probes. RESULTS : The carrier frequency and gene frequency of HLA-A*02:06 were 37.5 % and 20.0 %, respectively, in patients, and 16.7 % and 9.6 %, respectively, in controls (p=0.018). The carrier frequency of HLA-C*03:04 was 30 % in patients and 10.8 % in controls, and gene frequency of HLA-C*03:04 was 15 % in patients and 5.4 % in controls (p=0.003). The carrier frequency and gene frequency of HLA-C*03:03 were 2.5 % and 1.3 %, respectively, in patients, and 20 % and 10.4 %, respectively, in controls (p=0.006). CONCLUSIONS : As per our results, we suggest that HLA-A*02:06 and HLA-C*03:04 might be positive markers for CM-SJS/TEN with SOC, and HLA-C*03:03 might be an indicator of protection against CM-SJS/TEN with SOC in the Korean population.

Mucocutaneous inflammation in the Ikaros Family Zinc Finger 1-keratin 5-specific transgenic mice

BACKGROUND

Our genomewide association study documented an association between cold medicine-related Stevens-Johnson syndrome/toxic epidermal necrolysis (CM-SJS/TEN) and Ikaros Family Zinc Finger 1 (IKZF1). Few studies examined biological and pathological functions of IKZF1 in mucosal immunity. We hypothesized that IKZF1 contributes to the mucocutaneous inflammation.

METHODS

Human skin and conjunctival tissues were obtained for immunohistological studies. Primary human conjunctival epithelial cells (PHCjECs) and adult human epidermal keratinocytes (HEKa) also used for gene expression analysis. We also generated K5-Ikzf1-EGFP transgenic mice (Ikzf1 Tg) by introducing the Ik1 isoform into cells expressing keratin 5, which is expressed in epithelial tissues such as the epidermis and conjunctiva, and then examined them histologically and investigated gene expression of the epidermis. Moreover, Ikzf1 Tg were induced allergic contact dermatitis.

RESULTS

We found that human epidermis and conjunctival epithelium expressed IKZF1, and in PHCjECs and HEKa, the expression of IKZF1 mRNA was upregulated by stimulation with polyI:C, a TLR3 ligand. In Ikzf1 Tg, we observed dermatitis and mucosal inflammation including the ocular surface. In contact dermatitis model, inflammatory infiltrates in the skin of Ikzf1 Tg were significantly increased compared with wild type. Microarray analysis showed that Lcn2, Adh7, Epgn, Ifi202b, Cdo1, Gpr37, Duoxa1, Tnfrsf4, and Enpp5 genes were significantly upregulated in the epidermis of Ikzf1 Tg compared with wild type.

CONCLUSION

Our findings support the hypothesis that Ikaros might participate in mucocutaneous inflammation.

Expression of prostaglandin E2 receptor subtypes in human pterygium and normal conjunctiva: immunohistochemical study

PURPOSE

In the present study, we aimed to evaluate the expression of EP receptors in primary and recurrent human pterygium tissues.

METHODS

Pterygium samples were collected from 65 patients with primary pterygium and 16 patients with recurrent pterygium. Normal conjunctival tissues were collected from nasal interpalpebral area from 17 patients without systemic and any other ocular pathology. Expression of EP receptors was evaluated by immunohistochemistry. The median value for each receptor staining score (RSS) was determined in normal conjunctival specimens. In this study, RSS of > median value was defined as positive staining or high expression and ≤ median value as negative staining or weak expression in specimens. Chi-square test was used for statistical analysis, and p value of less than 0.05 was considered significant.

RESULTS

Stromal expression of EP1 was significantly higher in primary and recurrent pterygium specimens compared to normal conjunctival tissues (p = 0.007 and p = 0.002, respectively). Epithelial expressions of EP2 and EP3 were significantly lower in primary pterygium specimens compared to normal conjunctival tissues (p = 0.005 and p < 0.0001, respectively), and stromal expressions were insignificant. Stromal expression of EP4 was significantly higher in primary and recurrent pterygium specimens compared to normal conjunctival tissues (p = 0.002 and p = 0.012, respectively).

CONCLUSIONS

Expression of EP receptors has been up- or downregulated in primary and recurrent pterygium tissues, and these receptors may play a role in formation and recurrence of pterygium.

Human Leukocyte Antigen Class I Genes Associated With Stevens-Johnson Syndrome and Severe Ocular Complications Following Use of Cold Medicine in a Brazilian Population

Importance

Describing the association with human leukocyte antigen (HLA) alleles could facilitate the understanding of increased risk factors for development of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) in patients with severe ocular complications (SOCs).

Objective

To investigate the association between HLA class I genes and cold medicine (CM)-associated SJS/TEN with SOCs.

Design, Setting, and Participants

This case-control study was conducted between February 8, 2013, and August 29, 2014. Thirty-nine Brazilian patients with CM-SJS/TEN of 74 patients with SJS/TEN with SOCs and 133 healthy Brazilian volunteers were enrolled. Human leukocyte antigen class I genes (HLA-A, HLA-B, and HLA-C) were examined to determine whether there was a genetic predisposition for CM-SJS/TEN with SOC. Patients were interviewed to identify possible etiologic factors. Data analysis was performed from April 14, 2013, to August 29, 2014.

Main Outcomes and Measures

Genetic predisposition for CM-SJS/TEN with SOCs by analysis of HLA class I genes.

Results

Of 74 patients included in the analysis, 32 (43%) were male; mean (SD) age was 36.01 [15.42] years. HLA-A*66:01 (odds ratio [OR], 24.0; 95% CI, 2.79-206.0; P < .001), HLA-B*44:03 (OR, 2.71; 95% CI, 1.11-6.65; P = .04), and HLA-C*12:03 (OR, 5.6; 95% CI, 1.67-18.80; P = .006) were associated with Brazilian CM-SJS/TEN with SOCs, and HLA-A*11:01 (OR, 0.074; 95% CI, 0.004-1.26; P = .008), HLA-B*08:01 (OR, 0.15; 95% CI, 0.02-1.15; P = .048), and HLA-B*51:01 (OR, 0.23; 95% CI, 0.05-1.03; P = .045) were inversely associated with Brazilian CM-SJS/TEN with SOCs (39 cases: 19 Pardo and 16 European ancestry; 14 males and 25 females; age, 35.2 [14.4] years; and 133 controls: 66 Pardo and 61 European ancestry; 55 males and 78 females; age, 41.2 [12.9] years). When multiple test correction within the HLA locus, HLA-A*66:01 and HLA-C*12:03 demonstrated associations. When participants were segregated into Pardo and locus is considered, HLA-A*66:01 was associated with CM-SJS/TEN with SOC among individuals of both ethnic groups (Pardo: OR, 12.2; 95% CI, 1.19-125.0; P = .03; and European: OR, 21.2; 95% CI, 0.97-465.0; P = .04). An association was observed only in the European cohort for HLA-B*44:03 (OR, 5.50; 95% CI, 1.47-20.50; P = .01) and HLA-C*12:03 (OR, 8.79; 95% CI, 1.83-42.20; P = .008).

Conclusions and Relevance

This study suggests that HLA-A*66:01 might be a marker for CM-SJS/TEN with SOCs in Brazilian individuals of Pardo and European ancestry and that HLA-B*44:03 and HLA-C*12:03 might be markers only in those of European ancestry. Moreover, HLA-A*11:01 might be a marker of resistance to CM-SJS/TEN with SOCs.

Cold medicine-related Stevens-Johnson syndrome/toxic epidermal necrolysis with severe ocular complications-phenotypes and genetic predispositions

Stevens–Johnson syndrome (SJS) is an acute inflammatory vesiculobullous reaction of the skin and mucosa, such as the ocular surface, oral cavity, and genitals. In patients with extensive skin detachment and a poor prognosis, the condition is called toxic epidermal necrolysis (TEN). Severe ocular complications (SOCs) appear in some–but not all–SJS/TEN patients who are diagnosed by dermatologists, and cold medicines including multi-ingredient cold medications and nonsteroidal anti-inflammatory drugs are the main causative drugs particularly for SJS/TEN with SOCs and all SJS and TEN. In this review, we focus on the genetic predisposition of cold medicine-related SJS/TEN (CM-SJS/TEN) with SOCs. CM-SJS/TEN with SOCs was strongly associated with HLA-A*02:06 and significantly associated with HLA-B*44:03 in Japanese individuals, significantly associated with HLA-B*44:03 in Indian and Brazilian individuals, and associated with HLA-A*02:06 in Korean individuals. In the first genome-wide association study (GWAS), we found an association between the prostaglandin E receptor 3 (PTGER3) gene and SJS/TEN with SOCs. In this study, we focused on CM-SJS/TEN with SOCs and found that the association of CM-SJS/TEN with SOCs became stronger than all SJS/TEN with SOCs. In the second GWAS, we found an association between the IKZF1 gene and CM-SJS/TEN with SOCs not only in Japanese, but also in Korean and Indian populations. Moreover, we found that TSHZ2 gene single nucleotide polymorphisms (SNPs) also showed especially low p values in the Japanese population; however, this association was not found in the Korean population. Furthermore, we investigated the interaction between susceptibility genes, and found multiplicative interactions of HLA-A*02:06 and TLR3 SNPs and additive interactions of HLA-A*02:06 and PTGER3 SNPs.

Inhibition of prostaglandin E2 receptor EP3 mitigates thrombin-induced brain injury

Prostaglandin E2 EP3 receptor is the only prostaglandin E2 receptor that couples to multiple G-proteins, but its role in thrombin-induced brain injury is unclear. In the present study, we exposed mouse hippocampal slice cultures to thrombin in vitro and injected mice with intrastriatal thrombin in vivo to investigate the role of EP3 receptor in thrombin-induced brain injury and explore its underlying cellular and molecular mechanisms. In vitro, EP3 receptor inhibition reduced thrombin-induced hippocampal CA1 cell death. In vivo, EP3 receptor was expressed in astrocytes and microglia in the perilesional region. EP3 receptor inhibition reduced lesion volume, neurologic deficit, cell death, matrix metalloproteinase-9 activity, neutrophil infiltration, and the number of CD68(+) microglia, but increased the number of Ym-1(+) M2 microglia. RhoA-Rho kinase levels were increased after thrombin injection and were decreased by EP3 receptor inhibition. In mice that received an intrastriatal injection of autologous arterial blood, inhibition of thrombin activity with hirudin decreased RhoA expression compared with that in vehicle-treated mice. However, EP3 receptor activation reversed this effect of hirudin. These findings show that prostaglandin E2 EP3 receptor contributes to thrombin-induced brain damage via Rho-Rho kinase-mediated cytotoxicity and proinflammatory responses.

Genetic Predisposition to Stevens-Johnson Syndrome With Severe Ocular Surface Complications

Stevens-Johnson syndrome (SJS) is an acute inflammatory vesiculobullous reaction of the skin and mucosa, including the ocular surface, oral cavity, and genitals. In patients with extensive skin detachment and a poor prognosis, the condition is termed toxic epidermal necrolysis (TEN). This review covers 4 topics: (1) ophthalmic SJS, (2) human leukocyte antigen (HLA) analysis, (3) genome-wide association studies, and (4) other pathogenic factors. Severe ocular complications (SOCs) develop in some SJS/TEN patients diagnosed by dermatologists. Cold medicine-related SJS/TEN (CM-SJS/TEN) with SOCs is associated with HLA-A*02:06 in Japanese and Koreans and HLA-B*44:03 in Japanese, Indians, and Brazilian whites. We conducted a genome-wide association study for CM-SJS/TEN with SOCs and found that IKZF1 single-nucleotide polymorphisms (SNPs) were significantly associated with CM-SJS/TEN with SOCs, and that the ratio of the Ik2/Ik1 isoforms might be influenced by these IKZF1 SNPs. Moreover, HLA-A*02:06 with TLR3 polymorphisms and HLA-A*02:06 with EP3 polymorphisms exerted additive effects in SJS/TEN with SOCs. EP3 is strongly downregulated in the conjunctival epithelium of SJS/TEN. Cold medicines including nonsteroidal antiinflammatory drugs, which are the main causative drugs for SJS/TEN with SOCs, downregulate the production of prostanoids, including PGE2. Because the PGE2-EP3 pathway suppresses the inflammation of the ocular surface, skin, and respiratory tract, downregulation of PGE2 by nonsteroidal antiinflammatory drugs or acetaminophen might significantly contribute to the onset of CM-SJS/TEN with SOCs. Cold medicines and infectious agents such as viruses or other microbes are both important in triggering the onset of SJS/TEN with SOCs.

Culture medium from TNF-α-stimulated mesenchymal stem cells attenuates allergic conjunctivitis through multiple antiallergic mechanisms

BACKGROUND

The immunomodulatory and anti-inflammatory functions of mesenchymal stem cells (MSCs) have been demonstrated in several autoimmune/inflammatory diseases, but their contribution to allergic conjunctivitis and underlying antiallergic mechanisms remain elusive.

OBJECTIVE

We sought to explore the clinical application of MSCs to experimental allergic conjunctivitis (EAC) and its underlying antiallergic mechanisms.

METHODS

Culture medium from TNF-α-stimulated, bone marrow-derived MSCs (MSC-CMT) was administered topically to mice with EAC, and the related allergic symptoms and biological changes were evaluated. Murine spleen-derived B cells, bone marrow-derived mast cells (MCs), and lung vascular endothelial cells were cultured in vitro to investigate the antiallergic MSC-CMT mechanisms.

RESULTS

Topical instillation of MSC-CMT significantly attenuated the clinical symptoms of short ragweed pollen-induced EAC, with a significant decrease in inflammatory cell frequency, nuclear factor κB p65 expression, and TNF-α and IL-4 production. In vitro MSC-CMT significantly inhibited the activation of MCs and B-cell IgE release and reduced histamine-induced vascular hyperpermeability. During EAC, MSC-CMT treatment also decreased IgE production, histamine release, enrichment and activation of MCs, and conjunctival vascular hyperpermeability. The MSC-CMT-mediated inhibition of B cells, MCs, and histamine and its antiallergic effects during EAC were abrogated when MSCs were pretreated with COX2 small interfering RNA.

CONCLUSIONS

Our findings provide compelling evidence that MSC-CMT inhibits EAC through COX2-dependent multiple antiallergic mechanisms and support the use of MSC-CMT as a novel strategy for treating allergic conjunctivitis.

Prostanoids in allergy

Prostanoids, which include prostaglandin and thromboxane, are metabolites of arachidonic acid released in various pathophysiological conditions. They induce a range of actions mediated through their respective receptors expressed on target cells. It has been demonstrated that each prostanoid receptor has multiple functions and that the effect of receptor stimulation can vary depending on context; this sometimes results in opposing effects, such as simultaneous excitatory and inhibitory outcomes. The balance between the production of each prostanoid and the expression of its receptors has been shown to be important for maintaining homeostasis but also involved in the development of various pathological conditions such as allergy. Here, we review the recent findings on the roles of prostanoids in allergy, especially focusing on atopic dermatitis and asthma.

Regulation of ocular surface inflammation by prostaglandin E receptor subtype EP3

We first investigated whether the prostaglandin (PG) E2-PGE receptor subtype EP3 axis regulates the development of murine experimental allergic conjunctivitis because it has been reported that this pathway negatively regulates allergic reactions in a murine allergic asthma model. We observed that EP3 is constitutively expressed in mice conjunctival epithelium. EP3 knockout mice demonstrated significantly increased eosinophil infiltration in conjunctiva after ragweed challenge compared with wild-type mice. Consistently, significantly higher expression of eotaxin-1 messenger RNA was observed in Ptger3-/- mice. Conversely, treatment of wild-type mice with an EP3-selective agonist significantly decreased eosinophil infiltration, which was blunted in Ptger3-/- mice. Expression of cyclooxygenase-2 and PGE synthases was upregulated and PGE2 content increased in the eyelids after ragweed challenge. These data suggest that PGE2 acts on EP3 in the conjunctival epithelium and downregulates the progression of experimental allergic conjunctivitis. We next examined and compared the expression of EP3 in human conjunctival epithelium in various ocular surface diseases. Human conjunctival epithelium expressed EP3-specific messenger RNA and EP3 protein. Although we could clearly find positive signals in the conjunctival epithelium from patients with noninflammatory ocular surface diseases such as conjunctivochalasis and pterygium, we could not find positive signals in that from those with inflammatory disorders such as Stevens-Johnson syndrome and ocular cicatricial pemphigoid. Likewise, expression of the PGE receptor subtype EP4 was clearly found in the conjunctival epithelium from patients with conjunctivochalasis and pterygium but not from patients with Stevens-Johnson syndrome and ocular cicatricial pemphigoid.

Emerging drugs for allergic conjunctivitis

INTRODUCTION

Allergic conjunctivitis (AC) is a very common disease, especially in association with allergic rhinitis but may also occur in isolated presentation. The treatment of AC has long been based on antihistamines, cromones and topical corticosteroids, but none of these drugs completely abolishes the clinical expression of AC.

AREAS COVERED

The development of new drugs for AC is analyzed highlighting the recent insights into the pathophysiological mechanisms of the disease. The major aim of development of drugs for AC is to have agents able to prevent the inflammatory effects of the interaction between the allergen and the specific IgE antibodies on mast cell surface. This may be obtained by blocking the effects of histamine (the main mediator of early allergic response) by H1-receptor antagonists, inhibiting the release of soluble factors able to recruit inflammatory cells (that sustain prolonged inflammation) by mast-cell stabilizers, inhibiting the effects of single mediators, inducing tolerance to the allergen by specific immunotherapy or even acting on factors related to activation and differentiation of T lymphocytes such as the toll-like receptors.

EXPERT OPINION

AC is an underestimated disease for which there is a search of more effective treatments. The availability of the drugs under current evaluation will allow more refined therapeutic strategies to apply according to the characteristics and the clinical severity of AC.

Neuronal prostaglandin E2 receptor subtype EP3 mediates antinociception during inflammation

The pain mediator prostaglandin E2 (PGE2) sensitizes nociceptive pathways through EP2 and EP4 receptors, which are coupled to Gs proteins and increase cAMP. However, PGE2 also activates EP3 receptors, and the major signaling pathway of the EP3 receptor splice variants uses inhibition of cAMP synthesis via Gi proteins. This opposite effect raises the intriguing question of whether the Gi-protein-coupled EP3 receptor may counteract the EP2 and EP4 receptor-mediated pronociceptive effects of PGE2. We found extensive localization of the EP3 receptor in primary sensory neurons and the spinal cord. The selective activation of the EP3 receptor at these sites did not sensitize nociceptive neurons in healthy animals. In contrast, it produced profound analgesia and reduced responses of peripheral and spinal nociceptive neurons to noxious stimuli but only when the joint was inflamed. In isolated dorsal root ganglion neurons, EP3 receptor activation counteracted the sensitizing effect of PGE2, and stimulation of excitatory EP receptors promoted the expression of membrane-associated inhibitory EP3 receptor. We propose, therefore, that the EP3 receptor provides endogenous pain control and that selective activation of EP3 receptors may be a unique approach to reverse inflammatory pain. Importantly, we identified the EP3 receptor in the joint nerves of patients with painful osteoarthritis.

Prostaglandin E2-EP3 axis in fine-tuning excessive skin inflammation by restricting dendritic cell functions

Prostaglandin E₂ (PGE₂) is produced in the skin and is suggested to play a role in the regulation of cutaneous immune homeostasis and responses. However, the multifaceted functions of PGE₂ continue to elude our understanding, especially because of the multiplicity of PGE₂ receptors—EP1, EP2, EP3, and EP4. While cAMP-elevating EP4 is known to activate the functions of cutaneous dendritic cells (DCs), including Langerhans cells (LCs) and dermal DCs, the role of cAMP-suppressing EP3 in this process remains unknown. Here we demonstrated that an EP3 receptor selective agonist, ONO-AE-248, inhibited chemotaxis and co-stimulatory molecule expressions of DCs in vitro. A suboptimal dose of antigen was sufficient to induce contact hypersensitivity in EP3-deficient mice. Intriguingly, EP3 deficiency did not impair skin inflammation at all when the antigen dose was sufficiently high. EP3 limited the functions of cutaneous DCs only when the antigen dose was low. In contrast to EP4, the observed unappreciated function of EP3 may stabilize the cutaneous DCs to halt the impetuous response to a suboptimal dose of antigen. Taken together, PGE₂-EP3 signaling is essential for fine-tuning excessive skin inflammation by restricting DC functions.

Rebamipide suppresses PolyI:C-stimulated cytokine production in human conjunctival epithelial cells

PURPOSE

We previously documented that ocular surface epithelial cells could regulate ocular surface inflammation and suggested that, while Toll-like receptor 3 upregulates, EP3, one of the prostaglandin E2 receptors, downregulates ocular surface inflammation. Others reported that rebamipide, a gastroprotective drug, could not only increase the gastric mucus production, but also suppressed gastric mucosal inflammation and that it was dominantly distributed in mucosal tissues. The eyedrop form of rebamipide, approved in Japan for use in the treatment of dry eye diseases, upregulates mucin secretion and production, thereby suppressing superficial punctate keratopathy on the ocular surface of patients with this disease. In the current study, we investigated whether rebamipide has anti- inflammatory effects on the ocular surface.

METHODS

To examine the effects of rebamipide on polyI:C-induced cytokine expression by primary human conjunctival epithelial cells, we used enzyme-linked immunosorbent assay and quantitative reverse transcription-polymerase chain reaction assay. We studied the effects of rebamipide on ocular surface inflammation in our murine experimental allergic conjunctivitis (EAC) model.

RESULTS

Rebamipide could suppress polyI:C-induced cytokine production and the expression of mRNAs for CXCL10, CXCL11, RANTES, MCP-1, and IL-6 in human conjunctival epithelial cells. In our EAC model, the topical administration of rebamipide suppressed conjunctival allergic eosinophil infiltration.

CONCLUSIONS

The topical application of rebamipide on the ocular surface might suppress ocular surface inflammation by suppressing the production of cytokines by ocular surface epithelial cells.

Prostaglandin E2 suppresses poly I: C-stimulated cytokine production via EP2 and EP3 in immortalized human corneal epithelial cells

PURPOSE

We previously reported that prostaglandin (PG) E2 acts as a ligand for prostaglandin E receptor 3 (EP3) in conjunctival epithelial cells, that it downregulates the progression of experimental murine allergic conjunctivitis, and that in human conjunctival epithelial cells it modulates the expression of polyI:C-induced proinflammatory genes via prostaglandin E receptor 2 (EP2) and EP3, suggesting that PGE2 might have important roles in ocular surface inflammation such as allergic conjunctivitis. Here, we investigated whether PGE2 also downregulates polyI:C-induced cytokine production in human corneal epithelial cells.

METHODS

We used enzyme-linked immunosorbent assay and quantitative reverse transcription-polymerase chain reaction to examine the effects of PGE2 on polyI:C-induced cytokine expression by immortalized human corneal-limbal epithelial cells (HCLE). Using reverse transcription-polymerase chain reaction, we examined the messenger RNA (mRNA) expression of the PGE2 receptor, EP1-4.

RESULTS

PGE2 significantly attenuated the expression of CC chemokine ligand (CCL)5 (P < 0.0005), CCL20 (P < 0.0005), C-X-C chemokine (CXCL)10 (P < 0.0005), CXCL11 (P < 0.05), and interleukin (IL)-6 (P < 0.005) in human corneal-limbal epithelial cells. Human corneal epithelial cells manifested the mRNA expression of EP2, EP3, and EP4, but not EP1. The EP2 agonist significantly suppressed the polyI:C-induced expression of CCL5 (P < 0.005), CXCL10 (P < 0.0005), and CXCL11 (P < 0.05) but not of CCL20 and IL-6. The EP3 agonist significantly suppressed the expression of CCL5 (P < 0.05), CCL20 (P < 0.005), CXCL10 (P < 0.0005), CXCL11 (P < 0.0005), and IL-6 (P < 0.005). The EP4 agonist failed to suppress cytokine production induced by polyI:C stimulation.

CONCLUSIONS

Our results show that in human corneal epithelial cells, PGE2 attenuated the mRNA expression and production of CCL5, CXCL10, and CXCL11 via both EP2 and EP3, and that the mRNA expression and production of CCL20 and IL-6 was attenuated only by EP3.

Molecular immunology of allergic conjunctivitis

PURPOSE OF REVIEW

Successful treatment of allergic eye disease depends on understanding the pathophysiology of ocular allergy. Thus, in this review, recent experimental and clinical research that has provided significant information about the immunopathology of allergic eye disease will be discussed.

RECENT FINDINGS

Recently, role of various cells, cytokines and chemokines has been scrutinized in the immunopathogenesis of ocular allergy. In this respect, current research highlights contribution of special molecules and cells in the development and clinical features of immunoglobulin E (IgE) and T-cell-mediated eye allergies.

SUMMARY

Recent findings in molecular immunology of ocular allergy, which comprise complex inflammatory conditions of the conjunctiva, have enabled us to better understand the pathophysiology of these diseases and have aided in the potential development of new therapeutic agents.

Ocular surface inflammation is regulated by innate immunity

On the ocular surface, as in the intestines and airway, the surface epithelium serves a critical function as the front-line defense of the mucosal innate immune system. Although the detection of microbes is arguably the most important task of the immune system, an exaggerated epithelial host defense reaction to endogenous bacteria may initiate and perpetuate inflammatory mucosal responses. In this review we first describe commensal bacteria found on the ocular surface, which is in contact with the ocular surface epithelium. We also discuss the innate immunity of the ocular surface epithelium and we present the allergic reaction regulated by ocular surface epithelial cells. We address ocular surface inflammation due to disordered innate immunity and we present our hypothesis that the onset of Stevens-Johnson syndrome (SJS) with severe ocular surface complications, a devastating ocular surface inflammatory disease, is strongly associated with abnormality of the innate immune system. In this review we raise the possibility that some ocular surface inflammatory diseases are pathogenetically related with a disordered innate immune response. Focusing on the innate immunity of the ocular surface might help to elucidate the pathogenesis of various ocular surface diseases.

Prostaglandin E receptor subtype EP3 expression in human conjunctival epithelium and its changes in various ocular surface disorders

Background

In our earlier genome-wide association study on Stevens-Johnson Syndrome (SJS) and its severe variant, toxic epidermal necrolysis (TEN), we found that in Japanese patients with these severe ocular surface complications there was an association with prostaglandin E receptor 3 (EP3) gene (PTGER3) polymorphisms. We also reported that EP3 is dominantly expressed in the ocular surface-, especially the conjunctival epithelium, and suggested that EP3 in the conjunctival epithelium may down-regulate ocular surface inflammation. In the current study we investigated the expression of EP3 protein in the conjunctiva of patients with various ocular surface diseases such as SJS/TEN, chemical eye burns, Mooren’s ulcers, and ocular cicatricial pemphigoid (OCP).

Methodology/Principal Findings

Conjunctival tissues were obtained from patients undergoing surgical reconstruction of the ocular surface due to SJS/TEN, chemical eye burns, and OCP, and from patients with Mooren's ulcers treated by resection of the inflammatory conjunctiva. The controls were nearly normal human conjunctival tissues acquired at surgery for conjunctivochalasis. We performed immunohistological analysis of the EP3 protein and evaluated the immunohistological staining of EP3 protein in the conjunctival epithelium of patients with ocular surface diseases. EP3 was expressed in the conjunctival epithelium of patients with chemical eye burns and Mooren’s ulcer and in normal human conjunctival epithelium. However, it was markedly down-regulated in the conjunctival epithelium of SJS/TEN and OCP patients.

Conclusions

We posit an association between the down-regulation of EP3 in conjunctival epithelium and the pathogenesis and pathology of SJS/TEN and OCP, and suggest a common mechanism(s) in the pathology of these diseases. The examination of EP3 protein expression in conjunctival epithelium may aid in the differential diagnosis of various ocular surface diseases.

Expression of interleukin-4 receptor α in human corneal epithelial cells

PURPOSE

We previously reported that human conjunctival epithelial cells expressed functioning interleukin-4 receptor α (IL-4Rα). In this study, we investigated whether human corneal epithelial cells also express functioning IL-4Rα.

METHODS

The presence of IL-4Rα mRNA and protein in human corneal epithelium was examined by reverse-transcriptase polymerase chain reaction (RT-PCR) and immunohistology, respectively. The cell surface expression of IL-4Rα and the transcripts upregulated upon IL-4Rα ligand (IL-4 or IL-13) stimulation were examined by flow cytometry and quantitative RT-PCR, respectively, using immortalized human corneal-limbal epithelial (HCLE) cells.

RESULTS

The mRNA and protein of IL-4Rα were detected in human corneal epithelium. Flow cytometry analysis showed the cell surface expression of IL-4Rα protein. Quantitative RT-PCR assay of HCLE cells showed the upregulation of the transcripts tumor necrosis factor alpha-induced protein 6 (TNFAIP6), RAS guanyl-releasing protein 1 (RASGRP1), carbonic anhydrase II (CA2), cytokine-inducible SH2-containing protein (CISH), hyaluronan synthase 3 (HAS3), calpain 14 (CAPN14), endothelin receptor type A (EDNRA), cathepsin C (CTSC), and lecithin retinol acyltransferase (LRAT) as well as human conjunctival epithelial cells.

CONCLUSION

Human corneal epithelial cells expressed functioning IL-4Rα, and stimulation of its ligands, IL-4 and IL-13, could induce the expression of various genes, e.g., antiinflammatory molecule genes such as TNFAIP6 and CISH and cellular differentiation and proliferation-related molecule genes such as RASGRP1, HAS3, EDNRA, and LRAT.

A GPR40 agonist GW9508 suppresses CCL5, CCL17, and CXCL10 induction in keratinocytes and attenuates cutaneous immune inflammation

G-protein coupled receptors (GPCR) exert diverse physiological functions, many of which are exploited therapeutically. The roles of GPCR in keratinocytes in immune response in the skin, however, remain poorly defined. In this study, we focused on Gi-coupled GPCR in keratinocytes and defined their actions in immunoactivation of cultured keratinocytes in vitro and immune reaction in the skin in vivo. We first activated HaCaT cells by tumor necrosis factor (TNF)-α and IFN-γ and examined effects of various ligands for GPCR on production of CCL17 and CCL5. Agonists for Gi-coupled receptors, particularly GW9508 for GPR40, inhibited CCL17 and CCL5 expression in a pertussis toxin-sensitive manner. The inhibitory effect by GW9508 was abrogated by depletion of GPR40 with RNA interference. GW9508 further suppressed expression of IL-11, IL-24, and IL-33 induced in HaCaT cells by TNF-α and IFN-γ. GW9508 also inhibited CCL5 and CXCL10 production by normal human epidermal keratinocytes. Administration of GW9508 topically to the skin in the challenging phase suppressed ear swelling in a repeated hapten application model and contact hypersensitivity with downregulation of CCL5 and CXCL10, respectively. Thus, in the skin, stimulation of Gi-coupled receptors attenuates induction of critical cytokines and chemokines by proinflammatory cytokines in keratinocytes and suppresses allergic inflammation in the skin.

Ocular surface inflammation mediated by innate immunity

This review addresses three subjects: the innate immunity of the ocular surface epithelium, innate immunity and ocular surface inflammation, and Stevens-Johnson syndrome (SJS) and abnormality of innate immunity. In innate immunity of the ocular surface epithelium, ocular surface epithelial cells respond selectively to microbial components and induce limited inflammation, whereas immune-competent cells such as macrophages can recognize various microbial components through Toll-like receptors (TLRs) and induce inflammation to exclude the microbes. The difference between macrophages and ocular surface epithelial cells may be caused by the dissimilarity in the degree of coexistence with commensal bacteria. The unique innate immune response of ocular surface epithelium might contribute to coexistence with commensal bacteria. In innate immunity and ocular surface inflammation, we speculate that an abnormality in the proper innate immunity of the ocular surface may result in ocular surface inflammation. Our investigation shows that TLR3 positively regulates the late-phase reaction of experimental allergic conjunctivitis, which causes reduced eosinophilic conjunctival inflammation in TLR3KO (knockout) mice and pronounced eosinophilic conjunctival inflammation in TLR3Tg mice. We also demonstrate that human ocular surface epithelial cells can be induced to express many transcripts, including antiviral innate immune response-related genes and allergy-related genes, through polyI:C stimulation. Furthermore, we show that IkappaBzeta KO mice exhibit severe, spontaneous ocular surface inflammation accompanied by the eventual loss of almost all goblet cells and spontaneous perioral inflammation. IkappaBzeta is induced by diverse pathogen-associated molecular patterns and regulates nuclear factor-kappaB activity, possibly to prevent excessive inflammation in the presence of bacterial components. The spontaneous ocular surface inflammation observed in IkappaBzeta KO mice suggested that dysfunction/abnormality of innate immunity can play a role in ocular surface inflammation. In SJS and abnormality of innate immunity, we considered the possibility that there may be an association between SJS and a disordered innate immune response. In gene expression analysis of CD14 cells, we found that IL4R gene expression was different in patients with SJS/toxic epidermal necrolysis (TEN) and controls on lipopolysaccharide stimulation, being downregulated in patients with SJS/TEN and slightly upregulated in the controls. The expression of IkappaBzeta- and interleukin (IL)-1alpha-specific mRNA in patients with SJS/TEN was lower than in normal controls after 1-hour culture. Although SJS/TEN can be induced by drugs, not all individuals treated with these drugs developed SJS/TEN. Because the incidence of SJS/TEN is very low, we suspected a genetic predisposition and performed single-nucleotide polymorphism (SNP) association analysis using candidate genes associated with innate immunity, apoptosis, or allergy. We found that TLR3 SNP rs.3775296 and IL4R SNP rs.1801275 (Gln551Arg) were strongly associated (P<0.0005) with SJS/TEN with ocular surface complications, FasL rs.3830150 SNP was mildly associated (P<0.005), and IL13 rs.20541 (Arg110Gln) and IkappaBzeta SNP rs.595788G/A exhibited a weak association (P<0.05). Genetic and environmental factors may play a role in an integrated cause of SJS, and there is the possibility of an association between SJS and a disordered innate immunity.

Association between prostaglandin E receptor 3 polymorphisms and Stevens-Johnson syndrome identified by means of a genome-wide association study

BACKGROUND

Stevens-Johnson syndrome (SJS) and its severe variant, toxic epidermal necrolysis (TEN), are acute inflammatory vesiculobullous reactions of the skin and mucosa. They often affect the ocular surface and can result in permanent visual dysfunction.

OBJECTIVES

We sought to discover genetic markers for SJS/TEN susceptibility.

METHODS

We performed a genome-wide association study with 60 patients and 300 control subjects. We applied stringent filter and visual assessments for selecting single nucleotide polymorphisms (SNPs) and a high false discovery rate threshold. We fine-mapped the region where a candidate SNP was found and confirmed the results by means of sequencing. We evaluated the function of agonist-activated prostaglandin E receptor 3 (EP3), the gene for which contained several SNPs, in regulating cytokine production in human conjunctival epithelial (CE) cells. The expression levels of EP3 in the CE cells from patients and control subjects were also compared.

RESULTS

We identified 3 SNPs that passed the false discovery rate threshold. One (rs17131450) was close to the EP3 gene. Therefore we analyzed the EP3 region in detail and identified 5 other SNPs. We confirmed the association between SJS/TEN and all 6 SNPs. Activated EP3 was expressed in control CE cells, and it suppressed polyI:C-stimulated cytokine production, suggesting that EP3 might help prevent ocular surface inflammation. Concordantly, the EP3 levels were much lower in the CE cells of the patients than in those of the control subjects.

CONCLUSION

We demonstrated, using both genetic and functional analyses, that EP3 could be a key player in the pathogenesis of SJS/TEN accompanied by ocular complications.

Selective activation of the prostaglandin E2 circuit in chronic injury-induced pathologic angiogenesis

PURPOSE

Cyclooxygenase (COX)-derived prostaglandin E(2) (PGE(2)) is a prevalent and established mediator of inflammation and pain in numerous tissues and diseases. Distribution and expression of the four PGE(2) receptors (EP1-EP4) can dictate whether PGE(2) exerts an anti-inflammatory or a proinflammatory and/or a proangiogenic effect. The role and mechanism of endogenous PGE(2) in the cornea, and the regulation of EP expression during a dynamic and complex inflammatory/reparative response remain to be clearly defined.

METHODS

Chronic or acute self-resolving inflammation was induced in mice by corneal suture or epithelial abrasion, respectively. Reepithelialization was monitored by fluorescein staining and neovascularization quantified by CD31/PECAM-1 immunofluorescence. PGE(2) formation was analyzed by lipidomics and polymorphonuclear leukocyte (PMN) infiltration quantified by myeloperoxidase activity. Expression of EPs and inflammatory/angiogenic mediators was assessed by real-time PCR and immunohistochemistry. Mice eyes were treated with PGE(2) (100 ng topically, three times a day) for up to 7 days.

RESULTS

COX-2, EP-2, and EP-4 expression was upregulated with chronic inflammation that correlated with increased corneal PGE(2) formation and marked neovascularization. In contrast, acute abrasion injury did not alter PGE(2) or EP levels. PGE(2) treatment amplified PMN infiltration and the angiogenic response to chronic inflammation but did not affect wound healing or PMN infiltration after epithelial abrasion. Exacerbated inflammatory neovascularization with PGE(2) treatment was independent of the VEGF circuit but was associated with a significant induction of the eotaxin-CCR3 axis.

CONCLUSIONS

These findings place the corneal PGE(2) circuit as an endogenous mediator of inflammatory neovascularization rather than general inflammation and demonstrate that chronic inflammation selectively regulates this circuit at the level of biosynthetic enzyme and receptor expression.

Immune mechanisms in allergic eye diseases: what is new?

PURPOSE OF REVIEW

The purpose of this review will be to focus on new findings that expand our understanding of the immune mechanisms occurring in the various forms of allergic eye disease and in experimental models, and some novel therapeutic approaches.

RECENT FINDINGS

The novel data encompass three main areas: effector mechanisms in allergic eye disease; cytokines and chemokines in conjunctival responses; combinations of drugs for improving treatment options for allergic eye disease.

SUMMARY

The term 'allergic eye disease' describes a spectrum of clinical conditions, ranging from the common, milder conditions of seasonal and perennial allergic conjunctivitis (SAC, PAC), to the rare and more severe diseases, vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC). These latter two diseases can involve the cornea, leading to impaired vision. Although there is an underlying allergic mechanism, each of these ocular surface conditions involves different cellular responses and much effort has been made to identify the molecular pathways, which could be used as potential targets for therapeutic intervention. Currently available drugs, in particular for chronic forms of disease, are inadequate and there is an urgent need for safer, more localized and effective treatment.

Prostanoids and inflammation: a new concept arising from receptor knockout mice

Prostanoids including various types of prostaglandins and thromboxanes are arachidonate metabolites produced and released in response to a variety of physiological and pathological stimuli and function to maintain the body homeostasis. Since cyclooxygenase, the enzyme initiating their biosynthesis, is inhibited by aspirin-like antipyretic, anti-inflammatory, and analgesic drugs, contribution of prostanoids to acute inflammation such as fever generation, pain sensitization, and inflammatory swelling has been recognized very early. On the other hand, since aspirin-like drugs generally show little effects on allergy and immunity, it has been believed that prostanoids play little roles in these processes. Prostanoids act on a family of G-protein-coupled receptors designated PGD receptor, PGE receptor subtypes EP1-EP4, PGF receptor, PGI receptor, and TX receptor to elicit their actions. Studies using mice deficient in each of these receptors have revealed that prostanoids indeed function in the above aspirin-sensitive processes. However, these studies have also revealed that prostanoids exert both pro-inflammatory and anti-inflammatory actions not only by acting as mediators of acute inflammation but also by regulating gene expression in mesenchymal and epithelial cells at inflammatory site. Such dual actions of prostanoids are frequently seen in immune and allergic reactions, where different type of prostanoids and their receptors often exert opposite actions in a single process. Thus, a new concept on the role of prostanoids in inflammation has arisen from studies using the receptor knockout mice.

Prostaglandin E(2)-EP(3) signaling suppresses skin inflammation in murine contact hypersensitivity

BACKGROUND

Prostaglandin (PG) E(2) exerts a variety of actions through 4 G protein-coupled receptors designated as EP(1), EP(2), EP(3), and EP(4). We have reported that PGE(2) acts on EP(3) in airway epithelial cells and exerts anti-inflammatory actions in ovalbumin-induced murine allergic asthma. Although EP(3) is also expressed in skin and PGE(2) is produced abundantly during skin allergic inflammation, the role of PGE(2)-EP(3) signaling in skin allergic inflammation remains unknown.

OBJECTIVE

We sought to investigate whether PGE(2)-EP(3) signaling exerts anti-inflammatory actions in skin allergic inflammation.

METHODS

We used a murine contact hypersensitivity (CHS) model and examined the role of EP(3) by using an EP(3)-selective agonist, ONO-AE-248 (AE248), and EP(3)-deficient mice. The inflammation was evaluated by the thickness and histology of the hapten-challenged ear. Inflammation-associated changes in gene expression and effects of AE248 were examined by means of microarray analysis of the skin. Localization of EP(3) was examined by staining for beta-galactosidase knocked in at the EP(3) locus in EP(3)-deficient mice. EP(3) action was also examined in cultured keratinocytes.

RESULTS

Administration of AE248 during the elicitation phase significantly suppressed CHS compared with that seen in vehicle-treated mice. Microarray analysis revealed that administration of AE248 inhibited the gene expression of neutrophil-recruiting chemokines, including CXCL1, at the elicitation site. X-gal staining in EP(3)-deficient mice revealed EP(3) expression in keratinocytes, which was further confirmed by anti-EP(3) antibody in wild-type mice. In cultured keratinocytes AE248 suppressed CXCL1 production induced by TNF-alpha.

CONCLUSION

PGE(2)-EP(3) signaling inhibits keratinocytes activation and exerts anti-inflammatory actions in murine CHS.