Betacellulin (BTC) Biases the EGFR To Dimerize with ErbB3.

There are 13 known endogenous ligands for the epidermal growth factor receptor (EGFR) and its closely related ErbB receptor family members. We previously reported that betacellulin (BTC) is more efficacious than epidermal growth factor (EGF) in mediating corneal wound healing, although the molecular basis for this difference was unknown. For the most part, differences between ligands can be attributed to variability in binding properties, such as the unique rate of association and dissociation, pH sensitivity, and selective binding to individual ErbB family members of each ligand. However, this was not the case for BTC. Despite being better at promoting wound healing via enhanced cell migration, BTC has reduced receptor affinity and weaker induction of EGFR phosphorylation. These data indicate that the response of BTC is not due to enhanced affinity or kinase activity. Receptor phosphorylation and proximity ligation assays indicate that BTC treatment significantly increases ErbB3 phosphorylation and EGFR-ErbB3 heterodimers when compared with EGF treatment. We observed that EGFR-ErbB3 heterodimers contribute to cell migration, because the addition of an ErbB3 antagonist (MM-121) or RNA interference-mediated knockdown of ErbB3 attenuates BTC-stimulated cell migration compared with EGF. Thus, we demonstrate that, despite both ligands binding to the EGFR, BTC biases the EGFR to dimerize with ErbB3 to regulate the biologic response.

Overdose Education and Naloxone Rescue Kits for Family Members of Individuals Who Use Opioids: Characteristics, Motivations, and Naloxone Use.

BACKGROUND: In response to the overdose epidemic, a network of support groups for family members in Massachusetts has been providing overdose education and naloxone rescue kits (OEN). The aims of this study were to describe the characteristics, motivations, and benefits of family members who receive OEN and to describe the frequency of naloxone used during an overdose rescue. METHODS: This cross-sectional, multisite study surveyed attendees of community support groups for family members of opioid users where OEN training was offered using a 42-item self-administered survey that included demographics, relationship to the individual using opioids, experience with overdose, motivations to receive OEN, and naloxone rescue kit use. RESULTS: Of 126 attendees who completed surveys at 8 sites, most attendees were white (95%), female (78%), married or partnered (74%), parents of an individual using opioids (85%), and providing financial support for the individual using opioids (52%). The OEN trainees (79%) were more likely than attendees not trained (21%) to be parents of an individual using opioids (91% vs. 65%, P < .05), to provide financial support to an individual using opioids (58% vs. 30%, P < .05), and to have witnessed an overdose (35% vs. 12%, P = .07). The major motivations to receive training were wanting a kit in their home (72%), education provided at the meeting (60%), and hearing about benefits from others (57%). Sixteen parents reported witnessing their child overdose, and 5 attendees had used naloxone successfully during an overdose rescue. CONCLUSIONS: Support groups for families of people who use opioids are promising venues to conduct overdose prevention trainings because attendees are motivated to receive training and will use naloxone to rescue people when witnessing an overdose. Further study is warranted to understand how to optimize this approach to overdose prevention in the community setting.

Fact vs. fiction: naloxone in the treatment of opioid-induced respiratory depression in the current era of synthetic opioids.

Opioid-induced respiratory depression (OIRD) deaths are ~80,000 a year in the US and are a major public health issue. Approximately 90% of fatal opioid-related deaths are due to synthetic opioids such as fentanyl, most of which is illicitly manufactured and distributed either on its own or as an adulterant to other drugs of abuse such as cocaine or methamphetamine. Other potent opioids such as nitazenes are also increasingly present in the illicit drug supply, and xylazine, a veterinary tranquilizer, is a prevalent additive to opioids and other drugs of abuse. Naloxone is the main treatment used to reverse OIRD and is available as nasal sprays, prefilled naloxone injection devices, and generic naloxone for injection. An overdose needs to be treated as soon as possible to avoid death, and synthetic opioids such as fentanyl are up to 50 times more potent than heroin, so the availability of new, higher-dose, 5-mg prefilled injection or 8-mg intranasal spray naloxone preparations are important additions for emergency treatment of OIRDs, especially by lay people in the community. Higher naloxone doses are expected to reverse a synthetic overdose more rapidly and the current formulations are ideal for use by untrained lay people in the community. There are potential concerns about severe withdrawal symptoms, or pulmonary edema from treatment with high-dose naloxone. However, from the perspective of first responders, the balance of risks would point to administration of naloxone at the dose required to combat the overdose where the risk of death is very high. The presence of xylazines as an adulterant complicates the treatment of OIRDs, as naloxone is probably ineffective, although it will reverse the respiratory depression due to the opioid. For these patients, hospitalization is particularly vital. Education about the benefits of naloxone remains important not only in informing people about how to treat emergency OIRDs but also how to obtain naloxone. A call to emergency services is also essential after administering naloxone because, although the patient may revive, they may overdose again later because of the short half-life of naloxone and the long-lasting potency of fentanyl and its analogs.

Sex differences in COVID-19 symptoms and outcomes in people with kidney failure treated with dialysis: a prospective cohort study.

BACKGROUND: People with kidney failure treated with dialysis are at increased risk of SARS-CoV-2 infection, and severe COVID-19 outcomes such as hospitalization and death. Though there are well-defined sex differences in outcomes for the general population with COVID-19, we do not know whether this translates into kidney failure populations. We aimed to estimate the differences in COVID-19 symptoms and clinical outcomes between males and females treated with maintenance dialysis. METHODS: In this prospective observational cohort study, we included adults treated with maintenance dialysis in Southern Alberta, Canada that tested positive for COVID-19 between March 2020 and February 2022. We examined the association between sex (dichotomized as male and female) with COVID-19 symptoms including fever, cough, malaise, shortness of breath, muscle joints/aches, nausea and/or vomiting, loss of appetite, diarrhea, headache, sore throat, and loss of smell/taste using chi-square or Fisher's exact tests. Secondary outcomes included 30-day hospitalization, ICU admission, and death. RESULTS: Of 1,329 cohort participants, 246 (18.5%) tested positive for SARS-CoV-2 and were included in our study, including 95 females (39%). Of 207 participants with symptoms assessed, females had less frequent fever (p = 0.003), and more nausea or vomiting (p = 0.003) compared to males, after correction for multiple testing. Males exhibited no symptoms 25% of the time, compared with 10% of females (p = 0.01, not significant when corrected for multiple testing). We did not identify statistically significant differences in clinical outcomes between the sexes, though vaccinated patients had lower odds of hospitalization. CONCLUSIONS: Sex differences in COVID-19 symptoms were identified in a cohort of patients treated with maintenance dialysis, which may inform sex-specific screening strategies in dialysis units. Further work is necessary to examine mechanisms for identified sex differences.

Epidermal Growth Factor Receptor Expression in the Corneal Epithelium.

A properly functioning cornea is critical to clear vision and healthy eyes. As the most anterior portion of the eye, it plays an essential role in refracting light onto the retina and as an anatomical barrier to the environment. Proper vision requires that all layers be properly formed and fully intact. In this article, we discuss the role of the epidermal growth factor receptor (EGFR) in maintaining and restoring the outermost layer of the cornea, the epithelium. It has been known for some time that the addition of epidermal growth factor (EGF) promotes the restoration of the corneal epithelium and patients using EGFR inhibitors as anti-cancer therapies are at increased risk of corneal erosions. However, the use of EGF in the clinic has been limited by downregulation of the receptor. More recent advances in EGFR signaling and trafficking in corneal epithelial cells have provided new insights in how to overcome receptor desensitization. We examine new strategies for overcoming the limitations of high ligand and receptor expression that alter trafficking of the ligand:receptor complex to sustain receptor signaling.

Rigorous antibiotic stewardship in the hospitalized elderly population: saving lives and decreasing cost of inpatient care.

BACKGROUND: There is limited literature evaluating the effect of antibiotic stewardship programmes (ASPs) in hospitalized geriatric patients, who are at higher risk for readmissions, developing Clostridioides difficile infection (CDI) or other adverse outcomes secondary to antibiotic treatments. METHODS: In this cohort study we compare the rates of 30 day hospital readmissions because of reinfection or development of CDI in patients 65 years and older who received ASP interventions between January and June 2017. We also assessed their mortality rates and length of stay. Patients were included if they received antibiotics for pneumonia, urinary tract infection, acute bacterial skin and skin structure infection or complicated intra-abdominal infection. The ASP team reviewed patients on antibiotics daily. ASP interventions included de-escalation of empirical or definitive therapy, change in duration of therapy or discontinuation of therapy. Treatment failure was defined as readmission because of reinfection or a new infection. A control group of patients 65 years and older who received antibiotics between January and June 2015 (pre-ASP) was analysed for comparison. RESULTS: We demonstrated that the 30 day hospital readmission rate for all infection types decreased during the ASP intervention period from 24.9% to 9.3%, P < 0.001. The rate of 30 day readmissions because of CDI decreased during the intervention period from 2.4% to 0.30%, P = 0.02. Mortality in the cohort that underwent ASP interventions decreased from 9.6% to 5.4%, P = 0.03. Lastly, antibiotic expenditure decreased after implementation of the ASP from $23.3 to $4.3 per adjusted patient day, in just 6 months. CONCLUSIONS: Rigorous de-escalation and curtailing of antibiotic therapies were beneficial and without risk for the hospitalized patients 65 years and over.

Cell and molecular biology of epidermal growth factor receptor.

The epidermal growth factor receptor (EGFR) has been one of the most intensely studied cell surface receptors due to its well-established roles in developmental biology, tissue homeostasis, and cancer biology. The EGFR has been critical for creating paradigms for numerous aspects of cell biology, such as ligand binding, signal transduction, and membrane trafficking. Despite this history of discovery, there is a continual stream of evidence that only the surface has been scratched. New ways of receptor regulation continue to be identified, each of which is a potential molecular target for manipulating EGFR signaling and the resultant changes in cell and tissue biology. This chapter is an update on EGFR-mediated signaling, and describes some recent developments in the regulation of receptor biology.

The role of endogenous epidermal growth factor receptor ligands in mediating corneal epithelial homeostasis.

PURPOSE: To provide a comprehensive study of the biological role and therapeutic potential of six endogenous epidermal growth factor receptor (EGFR) ligands in corneal epithelial homeostasis. METHODS: Kinetic analysis and dose response curves were performed by using in vitro and in vivo wound-healing assays. Biochemical assays were used to determine receptor expression and activity. Human tears were collected and quantitatively analyzed by multianalyte profiling for endogenous EGFR ligands. RESULTS: Epidermal growth factor receptor ligands improved wound closure and activated EGFR, but betacellulin (BTC) was the most efficacious promoter of wound healing in vitro. In contrast, only epidermal growth factor (EGF) promoted wound healing in vivo. Human tears from 25 healthy individuals showed EGFR ligands at these average concentrations: EGF at 2053 ± 312.4 pg/mL, BTC at 207 ± 39.4 pg/mL, heparin-binding EGF at 44 ± 5.8 pg/mL, amphiregulin at 509 ± 28.8 pg/mL, transforming growth factor-α at 84 ± 19 pg/mL, and epiregulin at 52 ± 15 pg/mL. CONCLUSIONS: Under unwounded conditions, only EGF was present at concentrations near the ligand's Kd for the receptor, indicating it is the primary mediator of corneal epithelial homeostasis. Other ligands were present but at concentrations 11- to 7500-fold less their Kd, preventing significant ligand binding. Further, the high levels of EGF and its predicted binding preclude receptor occupancy by exogenous ligand and can explain the discrepancy between the in vitro and in vivo data. Therefore, therapeutic use of EGFR ligands may be unpredictable and impractical.

Stochastic humoral immunity to Bacillus anthracis protective antigen: identification of anti-peptide IgG correlating with seroconversion to Lethal Toxin neutralization.

A substantial fraction of individuals vaccinated against anthrax have low to immeasurable levels of serum Lethal Toxin (LeTx)-neutralizing activity. The only known correlate of protection against Bacillus anthracis in the currently licensed vaccine is magnitude of the IgG response to Protective Antigen (PA); however, some individuals producing high serum levels of anti-PA IgG fail to neutralize LeTx in vitro. This suggests that non-protective humoral responses to PA may be immunodominant in some individuals. Therefore, to better understand why anthrax vaccination elicits heterogeneous levels of protection, this study was designed to elucidate the relationship between anti-PA fine specificity and LeTx neutralization in response to PA vaccination. Inbred mice immunized with recombinant PA produced high levels of anti-PA IgG and neutralized LeTx in vitro and in vivo. Decapeptide binding studies using pooled sera reproducibly identified the same 9 epitopes. Unexpectedly, sera from individual mice revealed substantial heterogeneity in the anti-PA IgG and LeTx neutralization responses, despite relative genetic homogeneity, shared environment and exposure to the same immunogen. This heterogeneity permitted the identification of specificities that correlate with LeTx-neutralizing activity. IgG binding to six decapeptides comprising two PA epitopes, located in domains I and IV, significantly correlate with seroconversion to LeTx neutralization. These results indicate that stochastic variation in humoral immunity is likely to be a major contributor to the general problem of heterogeneity in vaccine responsiveness and suggest that vaccine effectiveness could be improved by approaches that focus the humoral response toward protective epitopes in a greater fraction of vaccinees.