Plateau iris syndrome: Epidemiology, diagnosis, and treatment: A narrative review.

Plateau iris syndrome (PIS) was first coined in 1958 to describe the iris configuration of a patient, 2 years later; the concept of plateau iris was published. In 1992, the anatomic aspects of plateau iris were studied using ultrasound biomicroscopy (UBM) determining it as a form of primary angle-closure glaucoma caused by a large or anteriorly positioned ciliary body that leads to mechanical obstruction of the trabecular meshwork, this condition is most often found in young patients. We aim to review the current literature and knowledge on the diagnosis and treatment options of PIS; the search was conducted in PubMed, LILACS, and BIREME internet search sites using keywords and snowball search strategy of articles published until 2022, focusing on PIS history, epidemiology, clinical diagnosis, UBM feature, and treatment.

Relationship between optic disc hemorrhage and glaucoma among patients diagnosed with systemic hypertension and Diabetes Mellitus: the Colombian Glaucoma Study / Relación entre Hemorragia de Disco Óptico y Glaucoma en pacientes con diagnóstico de Hipertensión Sistémica y Diabetes Mellitus: Estudio Colombiano de Glaucoma

Introduction: Glaucoma is a leading cause of irreversible blindness worldwide; several risk factors have been identified as major underlying causes for developing this condition. Optic disc hemorrhage has been identified as a risk factor for the development and progression of primary open-angle glaucoma, as well it has been related to playing an important role in normal-tension glaucoma. Material and methods: A cross-sectional study was conducted in Colombia among hypertensive and diabetic patients. This study included 2,067 subjects older than 50 years who were attended by a group of ophthalmologists in six cities in Colombia who conducted a complete medical and ophthalmological examination and applied standardized questionnaires and interviews aiming to evaluate participant’s health conditions and lifestyles. Results: We found a prevalence of Optic disc hemorrhage (ODH) of 0.4%. ODH presented an OR: 8.82 (95% CI 1.60 - 48.52) for the presence of Glaucoma. Patients diagnosed with systemic hypertension had an OR: 0.02 (95% CI 0.00 - 0.96); Patients with Retinal Nerve Fiber Layer Defect (RNFL) presented an OR: 509.40 (95% CI 8.60 - 30152.97) for the presence of ODH and 50% of patients with ODH did not have a diagnosis of glaucoma. Conclusions: Despite the low prevalence of ODH in our study (0.4%), its presence is a High-risk factor for the presence of Glaucoma. RNFL defect is also highly related to ODH and the presence of Glaucoma. (AU)

Introducción: El glaucoma es una de las principales causas de ceguera irreversible a nivel mundial; varios factores de riesgo han sido identificados como las principales causas subyacentes para el desarrollo de esta condición. La hemorragia del disco óptico se ha identificado como un factor de riesgo para el desarrollo y progresión del glaucoma primario de ángulo abierto, así como también se ha relacionado con desempeñar un papel importante en el glaucoma de tensión normal. Material y métodos: Se realizó un estudio transversal en Colombia entre pacientes hipertensos y diabéticos. Este estudio incluyó a 2.067 sujetos mayores de 50 años que fueron atendidos por un grupo de oftalmólogos en seis ciudades de Colombia, quienes realizaron un examen médico y oftalmológico completo y aplicaron cuestionarios y entrevistas estandarizados con el fin de evaluar las condiciones de salud y estilos de vida de los participantes. Resultados: Encontramos una prevalencia de hemorragia del disco óptico (HDO) del 0,4%. ODH presentó un OR: 8,82 (IC 95% 1,60 - 48,52) para la presencia de Glaucoma. Los pacientes diagnosticados de hipertensión sistémica tuvieron OR: 0,02 (IC 95% 0,00 - 0,96); Los pacientes con Defecto de la Capa de Fibras Nerviosas de la Retina (RNFL) presentaron un OR: 509,40 (IC 95% 8,60 - 30152,97) para la presencia de ODH y el 50% de los pacientes con ODH no tenían diagnóstico de glaucoma. Conclusiones: A pesar de la baja prevalencia de HDO en nuestro estudio (0,4%), su presencia es un factor de alto riesgo para la presencia de Glaucoma. El defecto de la RNFL también está muy relacionado con la ODH y la presencia de glaucoma. (AU)

Safety of Baricitinib 4 mg for the Treatment of Moderate to Severe Rheumatoid Arthritis.

OBJECTIVE: We evaluated the safety of baricitinib 4 mg at 24 weeks for the treatment of moderate to severe rheumatoid arthritis (RA). METHODS: Multiple databases were searched from inception up to November 26, 2019 for randomized controlled trials comparing baricitinib 4 mg with placebo for the treatment of moderate to severe RA. The safety outcomes of interest were the incidence of serious adverse events, adverse events leading to study discontinuation, all infections, and serious infections. Adjusted risk ratios (RRs) with 95% confidence intervals (CIs) were pooled for safety outcomes. The Cochrane tool was used to assess the risk of bias. RESULTS: This analysis included four randomized controlled trials with 3106 patients. For serious adverse events, the pooled RR (95% CI) was 1.09 (0.76-1.57). For adverse events leading to study discontinuation, the pooled RR (95% CI) was 1.41 (0.94-2.11). For all reported infections, the pooled RR (95% CI) was 1.24 (1.10-1.40), For serious infections, pooled RR (95% CI) was 0.97 (0.51-2.57). CONCLUSIONS: Patients with RA taking 4 mg baricitinib daily did have an increased risk of infections; however, the incidence of serious adverse events, adverse events leading to study discontinuation, or serious infections were not significantly different in patients treated with baricitinib 4 mg compared with placebo.

Impact of a Novel Post-Discharge Transitions of Care Clinic on Hospital Readmissions.

BACKGROUND: The Center for Medicare and Medicaid Services (CMS) has targeted hospital readmissions, which cost $17 billion per year, as one potential solution to reduce rising health care costs. Studies have documented the ability of Transitions of care (TOC) services to reduce readmissions in high risk patients. However, the vast majority of studies have not explored TOC services for all-cause admissions nor TOC clinics led by hospitalists. The goal of this study is to provide preliminary data regarding the potential effectiveness of a hospitalist-led TOC clinic servicing all patients on hospital readmission rates. METHODS: This cross-sectional feasibility study analyzed patients on a tertiary hospital teaching service. All discharged patients from January 2016 to September 2018 were given an appointment at the TOC clinic within 14 days of discharge. The control group consisted of patients assigned to the teaching service from January 2018 to November 2018 that were not offered a TOC appointment. RESULTS: Overall, 1373 patients (n = 1373) were included in this study between January 2016 and September 2018. The control group consisted of 1000 patients who were not offered follow up in the TOC clinic while the TOC group consisted of 373 patients who did attend a follow up appointment in the TOC clinic. The study participants (n = 1373) included patients admitted to the hospital for any diagnosis and were analyzed for all cause readmission rates. The TOC group consisted of 52% African Americans, 52% Medicare patients and 8% Medicaid patients. Demographic information for the control group was not available. The TOC group had a statistically significant 42% decreased risk of being readmitted within 30 days of discharge (RR = 0.58, 95% CI: 0.40-0.83). These data showed a statistically significant difference between the TOC group and control group in relation to the incidence of 30-day readmissions (p-value = 0.002). CONCLUSION: Among Medicare and Medicaid beneficiaries and commercial health insurance patients, this hospitalist-led TOC intervention was associated with a statistically significant reduction in 30-day readmissions following discharge for all-cause hospital admissions.

A Case Report of Disseminated Blastomycosis With Thyroid Involvement in a Pregnant Patient.

Blastomyces dermatitidis is the causal agent of blastomycosis, an invasive and often serious fungal infection. Blastomycosis typically presents as a pulmonary infection, but common extrapulmonary manifestations of blastomycosis include the skin, bones, and reticuloendothelial systems. Disseminated blastomycosis occurs more prominently in immunocompromised individuals, such as organ transplant recipients, HIV patients, and pregnant women. We report here a rare case of disseminated blastomycosis to the thyroid in a pregnant patient. This case emphasizes the unique challenges of diagnosing and treating disseminated fungal infections in pregnancy.

Choice of Intravenous Crystalloid Fluid and Mortality in Critically Ill Adult Patients.

OBJECTIVES: Intravenous balanced crystalloid fluid therapy may improve mortality and other outcomes in critically ill adult patients, but data are conflicting. We conducted a meta-analysis and literature review to evaluate the impact of intravenous balanced crystalloid, as compared with normal saline, fluid therapy on outcomes in critically ill adult patients. METHODS: We searched PubMed, Scopus, MEDLINE, and the Cochrane Register of Clinical Trials for relevant studies. Randomized controlled trials comparing the effects of balanced intravenous crystalloids with normal saline on intensive care unit (ICU) or hospital mortality were included. Pooled risk ratios (RRs) were calculated using a fixed effects model. Heterogeneity was calculated using the I2 statistic. The risk of bias was assessed using the Cochrane tool. RESULTS: Seven randomized controlled trials with 20,171 patients (10,179 participants received balanced crystalloids and 9992 participants received normal saline) were included. For hospital mortality, the pooled RR (95% confidence interval [CI]) was 0.92 (0.85-1.00). For ICU mortality, the pooled RR (95% CI) was 0.91 (0.82-1.00). For major adverse kidney events at 30 days, pooled RR (95% CI) was 0.95 (0.88-1.01). For stage ≥2 acute kidney injury, the pooled RR (95% CI) was 0.94 (0.86-1.02). For receipt of new renal replacement therapy, the pooled RR (95% CI) was 0.91 (0.77-1.07). None of these findings reached statistical significance. CONCLUSIONS: Intravenous balanced crystalloid use, compared with normal saline, does not result in a statistically significant reduction in hospital or ICU mortality, major adverse kidney events at 30 days, stage ≥2 acute kidney injury, or receipt of new renal replacement therapy in critically ill adult patients.

Cryptogenic Stroke and Significance of the Patent Foramen Ovale: A Case Series.

Stroke is the second leading cause of death globally and can lead to significant adverse outcomes in patients following the acute illness. Due to this high morbidity and mortality, adequate interventions can play a significant role in health outcomes. Patent foramen ovale is one of the major proposed causes of cryptogenic strokes and can be present in up to 25% of general population. In cryptogenic strokes, the relation of this structural heart defect is inversely proportional to age of patient. Here, we present three cases of cryptogenic strokes in patients with patent foramen ovale where it possibly plays a significant role. We demonstrate that in the younger age spectrum, patent foramen ovale plays a more significant role and treatment could prevent future stroke episodes.

Beneficial Effects of Statins on the Rates of Hepatic Fibrosis, Hepatic Decompensation, and Mortality in Chronic Liver Disease: A Systematic Review and Meta-Analysis.

OBJECTIVES: Statins may improve outcomes in patients with chronic liver disease (CLD). We conducted a systematic review and meta-analysis to evaluate the impact of statins in the setting of CLD. METHODS: We searched several databases from inception to 17 October 2016 to identify comparative studies evaluating the role of statins in CLD. Outcomes of interest were the associations between statin use and progression of fibrosis, development of hepatic decompensation in cirrhosis, and mortality in CLD. Adjusted hazard ratios (HRs) were pooled and analyzed using a random effects model. Subgroup analyses were performed based on the method of detection for progression of hepatic fibrosis and quality of studies. RESULTS: We included 10 studies (1 randomized controlled trial and 9 observational) with 259,453 patients (54,441 statin users and 205,012 nonusers). For progression of hepatic fibrosis, pooled HR (95% confidence interval) was 0.49 (0.39-0.62). On subgroup analysis of studies using ICD-9 (The International Classification of Diseases, Ninth Revision) coding and a second method to detect cirrhosis, pooled HR was 0.58 (0.51-0.65); pooled HR for studies using ICD-9 coding only was 0.36 (0.29-0.44). For progression of fibrosis in patients with hepatitis C virus (HCV) infection, pooled HR was 0.52 (0.37-0.73). For hepatic decompensation in cirrhosis, pooled HR was 0.54 (0.46-0.65). For mortality, pooled HR based on observational studies was 0.67 (0.46-0.98); in the randomized controlled trial, HR was 0.39 (0.15-0.99). However, the quality of evidence for these associations is low as most included studies were retrospective in nature and limited by residual confounding. CONCLUSIONS: Statins may retard the progression of hepatic fibrosis, may prevent hepatic decompensation in cirrhosis, and may reduce all-cause mortality in patients with CLD. As the quality (certainty) of evidence is low, further studies are needed before statins can be routinely recommended.

Disseminated Nocardia Farcinica Pneumonia with Left Adrenal Gland Abscess.

Adrenal masses pose a diagnostic challenge. The differential diagnosis includes functional adrenal tumors, incidentally found adrenal masses, metastases from an unknown primary cancer, and abscesses. Infrequently, adrenal gland abscesses have been reported in disseminated nocardiosis affecting immunocompetent and immunocompromised patients. We report a case of disseminated Nocardia farcinica pneumonia with an adrenal gland abscess in an immunocompetent patient with no identified risk factors for nocardiosis.

Does Urgent Colonoscopy Improve Outcomes in the Management of Lower Gastrointestinal Bleeding?

Colonoscopy continues to be an essential diagnostic and therapeutic tool in the management of lower gastrointestinal bleeding (LGIB). Studies that have evaluated the role of urgent colonoscopy for treating LGIB have reached conflicting conclusions. We conducted a systematic review and meta-analysis to evaluate the role of urgent colonoscopy in several outcomes in patients with LGIB. We searched Medline, Embase, Scopus and Cochrane databases from inception to July 10, 2016 for comparative studies evaluating the role of urgent versus elective colonoscopy in the management of LGIB. We evaluated mortality, rate of rebleeding, length of stay in hospital, identification of bleeding source, stigmata of recent hemorrhage and need for surgery. Pooled odds ratios (OR) were calculated for dichotomous variables whereas standard mean differences were calculated for continuous variables. We assessed quality using the Cochrane tool and Newcastle Ottawa Scale for randomized controlled trials and observational studies, respectively. We used the GRADE framework to interpret our findings. A total of 6 studies (2 randomized controlled trials and 4 observational studies) with 23,419 patients (9,498 urgent colonoscopy and 13,921 elective colonoscopy) were included in this meta-analysis. Pooled ORs with 95% CI for mortality, rebleeding and identification of bleeding source were 0.84 (0.46-1.53), 1.18 (0.64-2.16) and 1.49 (0.86-2.59), respectively. Stigmata of recent hemorrhage were more readily identified with urgent colonoscopy OR 2.85 (1.90-4.28). There were no differences in requirement for surgery, length of hospital stay or rate of endoscopic intervention. However, these effect sizes were limited by considerable heterogeneity, which was probably due to studies being conducted in different countries having different criteria for discharge and on variations in the type of endoscopic therapy for stigmata of recent hemorrhage. In conclusion, among patients with acute LGIB, there is no evidence that urgent colonoscopy reduces mortality, rebleeding or requirement for surgery or that it improves the rate of identification of the bleeding source. However, urgent colonoscopy does increase the rate of detection of stigmata of recent hemorrhage.

Health City Cayman Islands and the globalization of health services delivery.

We describe a new health care campus under development in the Cayman Islands, Health City, based on the low-cost "focused factory" model. The construction of a multispecialty hospital opening in February 2014 less than a 4-hour flight away from the United States and convenient to both Central and South America for patients who already travel to the United States for clinical care could reshape the US health care marketplace and enhance access to affordable specialty health care in the region.

Epidermal growth factor protects the apical junctional complexes from hydrogen peroxide in bile duct epithelium.

The tight junctions of bile duct epithelium form a barrier between the toxic bile and liver parenchyma. Disruption of tight junctions appears to have a crucial role in the pathogenesis of various liver diseases. In this study, we investigated the disruptive effect of hydrogen peroxide and the protective effect of epidermal growth factor (EGF) on the tight junctions and adherens junctions in the bile duct epithelium. Oxidative stress in NRC-1 and Mz-ChA-1 cell monolayers was induced by administration of hydrogen peroxide. Barrier function was evaluated by measuring electrical resistance and inulin permeability. Integrity of tight junctions, adherens junctions and the actin cytoskeleton was determined by imunofluorescence microscopy. Role of signaling molecules was determined by evaluating the effect of specific inhibitors. Hydrogen peroxide caused a rapid disruption of tight junctions and adherens junctions leading to barrier dysfunction without altering the cell viability. Hydrogen peroxide rapidly increased the levels of p-MLC (myosin light chain) and c-Src(pY418). ML-7 and PP2 (MLCK and Src kinase inhibitors) attenuated hydrogen peroxide-induced barrier dysfunction, tight junction disruption and reorganization of actin cytoskeleton. Pretreatment of cell monolayers with EGF ameliorated hydrogen peroxide-induced tight junction disruption and barrier dysfunction. The protective effect of EGF was abrogated by ET-18-OCH(3) and the Ro-32-0432 (PLCγ and PKC inhibitors). Hydrogen peroxide increased tyrosine phosphorylation of ZO-1, claudin-3, E-cadherin and ß-catenin, and pretreatment of cells with EGF attenuated tyrosine phosphorylation of these proteins. These results demonstrate that hydrogen peroxide disrupts tight junctions, adherens junctions and the actin cytoskeleton by an MLCK and Src kinase-dependent mechanism in the bile duct epithelium. EGF prevents hydrogen peroxide-induced tight junction disruption by a PLCγ and PKC-dependent mechanism.

Protein kinase Cζ phosphorylates occludin and promotes assembly of epithelial tight junctions.

Protein kinases play an important role in the regulation of epithelial tight junctions. In the present study, we investigated the role of PKCζ (protein kinase Cζ) in tight junction regulation in Caco-2 and MDCK (Madin-Darby canine kidney) cell monolayers. Inhibition of PKCζ by a specific PKCζ pseudosubstrate peptide results in redistribution of occludin and ZO-1 (zona occludens 1) from the intercellular junctions and disruption of barrier function without affecting cell viability. Reduced expression of PKCζ by antisense oligonucleotide or shRNA (short hairpin RNA) also results in compromised tight junction integrity. Inhibition or knockdown of PKCζ delays calcium-induced assembly of tight junctions. Tight junction disruption by PKCζ pseudosubstrate is associated with the dephosphorylation of occludin and ZO-1 on serine and threonine residues. PKCζ directly binds to the C-terminal domain of occludin and phosphorylates it on threonine residues. Thr403, Thr404, Thr424 and Thr438 in the occludin C-terminal domain are the predominant sites of PKCζ-dependent phosphorylation. A T424A or T438A mutation in full-length occludin delays its assembly into the tight junctions. Inhibition of PKCζ also induces redistribution of occludin and ZO-1 from the tight junctions and dissociates these proteins from the detergent-insoluble fractions in mouse ileum. The present study demonstrates that PKCζ phosphorylates occludin on specific threonine residues and promotes assembly of epithelial tight junctions.

Hydrogen peroxide activates focal adhesion kinase and c-Src by a phosphatidylinositol 3 kinase-dependent mechanism and promotes cell migration in Caco-2 cell monolayers.

Recent studies showed that c-Src and phosphatidylinositol 3 (PI3) kinase mediate the oxidative stress-induced disruption of tight junctions in Caco-2 cell monolayers. The present study evaluated the roles of PI3 kinase and Src kinase in the oxidative stress-induced activation of focal adhesion kinase (FAK) and acceleration of cell migration. Oxidative stress, induced by xanthine and xanthine oxidase system, rapidly increased phosphorylation of FAK on Y397, Y925, and Y577 in the detergent-insoluble and soluble fractions and increased its tyrosine kinase activity. The PI3 kinase inhibitors, wortmannin and LY294002, and the Src kinase inhibitor, 4-amino-5[chlorophyll]-7-[t-butyl]pyrazolo[3-4-d]pyrimidine, attenuated tyrosine phosphorylation of FAK. Oxidative stress induced phosphorylation of c-Src on Y418 by a PI3 kinase-dependent mechanism, whereas oxidative stress-induced activation of PI3 kinase was independent of Src kinase activity. Hydrogen peroxide accelerated Caco-2 cell migration in a concentration-dependent manner. Promotion of cell migration by hydrogen peroxide was attenuated by LY294002 and PP2. Reduced expression of FAK by siRNA attenuated hydrogen peroxide-induced acceleration of cell migration. The expression of constitutively active c-Src(Y527F) enhanced cell migration, whereas the expression of dominant negative c-Src(K296R/Y528F) attenuated hydrogen peroxide-induced stimulation of cell migration. Oxidative stress-induced activation of c-Src and FAK was associated with a rapid increase in the tyrosine phosphorylation and the levels of paxillin and p130(CAS) in actin-rich, detergent-insoluble fractions. This study shows that oxidative stress activates FAK and accelerates cell migration in an intestinal epithelium by a PI3 kinase- and Src kinase-dependent mechanism.

Protein phosphatase 2A plays a role in hydrogen peroxide-induced disruption of tight junctions in Caco-2 cell monolayers.

Evidence indicates that PP2A (protein phosphatase 2A) interacts with epithelial tight junctions and negatively regulates the integrity of the tight junction. In the present study, the role of PP2A in the hydrogen peroxide-induced disruption of the tight junction was examined in Caco-2 cell monolayers. Hydrogen peroxide-induced decrease in electrical resistance and increase in inulin permeability was associated with the dephosphorylation of occludin on threonine residues. The hydrogen peroxide-induced decrease in electrical resistance, increase in inulin permeability and redistribution of occludin and ZO (zonula occludens)-1 from the intercellular junctions were significantly attenuated by selective inhibitors of PP2A (okadaic acid and fostriecin) and by knockdown of PP2A-Calpha (the catalytic subunit of PP2A). The PP2A-Calpha protein and PP2A activity were co-immunoprecipitated with occludin, and this co-immunoprecipitation was rapidly increased by hydrogen peroxide. Hydrogen peroxideinduced increase in co-immunoprecipitation of PP2A-Calpha with occludin was prevented by PP2, a Src kinase inhibitor. GST (glutathione transferase)-pull down assays using recombinant GST-Occludin-C (C-terminal tail of occludin) and the purified PP2A showed that PP2A binds to the C-terminal domain of occludin; Src-induced tyrosine phosphorylation of GST-Occludin-C enhanced this binding. The present study shows that hydrogen peroxide increases the association of PP2A with occludin by a Src kinase-dependent mechanism, and that PP2A activity is involved in hydrogen peroxide-induced disruption of tight junctions in Caco-2 cell monolayers.

PKC eta regulates occludin phosphorylation and epithelial tight junction integrity.

PKC eta is expressed predominantly in the epithelial tissues; however, its role in the regulation of epithelial tight junctions (TJs) is unknown. We present evidence that PKC eta phosphorylates occludin on threonine residues (T403 and T404) and plays a crucial role in the assembly and/or maintenance of TJs in Caco-2 and MDCK cell monolayers. Inhibition of PKC eta by specific pseudo substrate inhibitor or knockdown of PKC eta by specific shRNA disrupts the junctional distribution of occludin and ZO-1 and compromises the epithelial barrier function. Expression of dominant negative, PKC eta(K394R) disrupts the TJ and barrier function, whereas wild-type PKC eta and constitutively active PKC eta(A161E) enhance the TJ integrity. Inhibition and knockdown of PKC eta or expression of PKC eta(K394R) induce dephosphorylation of occludin on threonine residues, whereas active PKC eta elevates occludin phosphorylation. PKC eta directly interacts with the C-terminal domain of occludin and phosphorylates it on highly conserved T403 and T404. T403/404A mutations result in the loss of occludin's ability to localize at the TJs, whereas T403/404D mutations attenuates the PKC eta inhibitor-mediated redistribution of occludin from the intercellular junctions. These results reveal an important mechanism of epithelial TJ regulation by PKC eta.

Phosphorylation of Tyr-398 and Tyr-402 in occludin prevents its interaction with ZO-1 and destabilizes its assembly at the tight junctions.

Occludin is phosphorylated on tyrosine residues during the oxidative stress-induced disruption of tight junction, and in vitro phosphorylation of occludin by c-Src attenuates its binding to ZO-1. In the present study mass spectrometric analyses of C-terminal domain of occludin identified Tyr-379 and Tyr-383 in chicken occludin as the phosphorylation sites, which are located in a highly conserved sequence of occludin, YETDYTT; Tyr-398 and Tyr-402 are the corresponding residues in human occludin. Deletion of YETDYTT motif abolished the c-Src-mediated phosphorylation of occludin and the regulation of ZO-1 binding. Y398A and Y402A mutations in human occludin also abolished the c-Src-mediated phosphorylation and regulation of ZO-1 binding. Y398D/Y402D mutation resulted in a dramatic reduction in ZO-1 binding even in the absence of c-Src. Similar to wild type occludin, its Y398A/Y402A mutant was localized at the plasma membrane and cell-cell contact sites in Rat-1 cells. However, Y398D/Y402D mutants of occludin failed to localize at the cell-cell contacts. Calcium-induced reassembly of Y398D/Y402D mutant occludin in Madin-Darby canine kidney cells was significantly delayed compared with that of wild type occludin or its T398A/T402A mutant. Furthermore, expression of Y398D/Y402D mutant of occludin sensitized MDCK cells for hydrogen peroxide-induced barrier disruption. This study reveals a unique motif in the occludin sequence that is involved in the regulation of ZO-1 binding by reversible phosphorylation of specific Tyr residues.

Role of phospholipase Cgamma-induced activation of protein kinase Cepsilon (PKCepsilon) and PKCbetaI in epidermal growth factor-mediated protection of tight junctions from acetaldehyde in Caco-2 cell monolayers.

Epidermal growth factor (EGF) protects the intestinal epithelial tight junctions from acetaldehyde-induced insult. The role of phospholipase Cgamma (PLCgamma) and protein kinase C (PKC) isoforms in the mechanism of EGF-mediated protection of tight junction from acetaldehyde was evaluated in Caco-2 cell monolayers. EGF-mediated prevention of acetaldehyde-induced decrease in transepithelial electrical resistance and an increase in inulin permeability, and subcellular redistribution of occludin and ZO-1 was attenuated by reduced expression of PLCgamma1 by short hairpin RNA. EGF induced a rapid activation of PLCgamma1 and PLC-dependent membrane translocation of PKCepsilon and PKCbetaI. Inhibition of PKC activity or selective interference of membrane translocation of PKCepsilon and PKCbetaI by RACK interference peptides attenuated EGF-mediated prevention of acetaldehyde-induced increase in inulin permeability and redistribution of occludin and ZO-1. BAPTA-AM and thapsigargin blocked EGF-induced membrane translocation of PKCbetaI and attenuated EGF-mediated prevention of acetaldehyde-induced disruption of tight junctions. EGF-induced translocation of PKCepsilon and PKCbetaI was associated with organization of F-actin near the perijunctional region. This study shows that PLCgamma-mediated activation of PKCepsilon and PKCbetaI and intracellular calcium is involved in EGF-mediated protection of tight junctions from acetaldehyde-induced insult.