Stabilized trimeric peptide immunogens of the complete HIV-1 gp41 N-heptad repeat and their use as HIV-1 vaccine candidates.

Efforts to develop an HIV-1 vaccine include those focusing on conserved structural elements as the target of broadly neutralizing monoclonal antibodies. MAb D5 binds to a highly conserved hydrophobic pocket on the gp41 N-heptad repeat (NHR) coiled coil and neutralizes through prevention of viral fusion and entry. Assessment of 17-mer and 36-mer NHR peptides presenting the D5 epitope in rodent immunogenicity studies showed that the longer peptide elicited higher titers of neutralizing antibodies, suggesting that neutralizing epitopes outside of the D5 pocket may exist. Although the magnitude and breadth of neutralization elicited by NHR-targeting antigens are lower than that observed for antibodies directed to other epitopes on the envelope glycoprotein complex, it has been shown that NHR-directed antibodies are potentiated in TZM-bl cells containing the FcγRI receptor. Herein, we report the design and evaluation of covalently stabilized trimeric 51-mer peptides encompassing the complete gp41 NHR. We demonstrate that these peptide trimers function as effective antiviral entry inhibitors and retain the ability to present the D5 epitope. We further demonstrate in rodent and nonhuman primate immunization studies that our 51-mer constructs elicit a broader repertoire of neutralizing antibody and improved cross-clade neutralization of primary HIV-1 isolates relative to 17-mer and 36-mer NHR peptides in A3R5 and FcγR1-enhanced TZM-bl assays. These results demonstrate that sensitive neutralization assays can be used for structural enhancement of moderately potent neutralizing epitopes. Finally, we present expanded trimeric peptide designs which include unique low-molecular-weight scaffolds that provide versatility in our immunogen presentation strategy.

The soil and the seed: The relationship between Descemet's membrane and the corneal endothelium.

Descemet's membrane (DM), the basement membrane of the corneal endothelium, is formed from the extracellular matrix (ECM) secreted by corneal endothelial cells. The ECM supports the growth and function of the corneal endothelial cells. Changes to DM are central to the diagnosis of the most common corneal endothelial disease, Fuchs endothelial corneal dystrophy (FECD). Changes in DM are also noted in systemic diseases such as diabetes mellitus. In FECD, the DM progressively accumulates guttae, "drop-like deposits" that disrupt the corneal endothelial cell monolayer. While the pathophysiologic changes to corneal endothelial cells in the course of FECD have been well described and reviewed, the changes to DM have received limited attention. The reciprocity of influence between the corneal endothelial cells and DM demands full attention to the latter in our search for novel treatment and preventive strategies. In this review, we discuss what is known about the formation and composition of DM and how it changes in FECD and other conditions. We review characteristics of guttae and the interplay between corneal endothelial cells and guttae, particularly as it might apply to future cell-based and genetic therapies for FECD.

Efficacy of skin-to-skin vs. cloth-to-cloth contact for thermoregulation in low birth weight newborns: a randomized crossover trial.

OBJECTIVE: Skin-to-skin contact (SSC) is effective to maintain normal temperature in low birth weight (LBW) newborns. However, there are several barriers related to privacy and space availability for its optimum utilization. We used cloth-to-cloth contact (CCC), i.e. placing the newborn in Kangaroo position without removing cloths as an innovative alternative to SSC to test its efficacy for thermoregulation and feasibility as compared to SSC in LBW newborns. METHODS: The newborns eligible for Kangaroo Mother Care (KMC) in step-down nursery were included in this randomized crossover trial. Newborns received SSC or CCC as per randomization on the first day and then crossed over to other group on the next day and so on. A feasibility questionnaire was asked to the mothers and the nurses. Axillary temperature was measured at various time intervals. Group comparisons were made by either using independent sample t-test or Chi-square test. RESULTS: A total of 23 newborns received KMC for total 152 occasions in the SSC group and 149 times in the CCC group. There was no significant temperature difference between the groups at any time-point. Mean (standard deviation) gain of temperature at 120 min in the CCC group [0.43 (0.34)°C] was comparable to the SSC group [0.49 (0.36)°C] (p = 0.13). We did not observe any adverse effect of CCC. Most mothers and nurses perceived CCC feasible in hospital settings and felt that it could be feasible in-home settings too. CONCLUSION: CCC was safe, more feasible and not inferior to SSC for maintaining thermoregulation in LBW newborns.

Skin-to-skin contact (SSC) helps in maintaining optimum temperature of low birth weight (LBW) newborns. It is an important component of Kangaroo Mother Care (KMC), which is standard of care and reduces several neonatal morbidities and mortality. However, there are several barriers for the optimum utilization of KMC. One of the major barriers is privacy issues while putting newborn in SSC. To overcome this barrier for increasing KMC uptake, we innovatively thought of keeping the newborn on mother's chest without removing the cloths of both the mother and the newborn. We called it cloth-to-cloth contact (CCC). We compared SSC and CCC for temperature regulation in the newborns weighing between 1500 and 2499 g at the time of enrollment using a crossover design. We observed that mean temperature steadily increased in newborns while receiving SSC or CCC for 2 h. There were no significant differences in mean temperature readings between these two groups at various time points. Thus, CCC was not inferior to SSC in maintaining temperature. We did not observe any adverse effect of CCC. CCC may overcome the barrier of privacy issues of SSC. Thus, CCC was equally efficacious, safe and more feasible for maintaining thermoregulation in LBW newborns.

The efficacy of 2 different phakic intraocular lens implant in keratoconus as an isolated procedure or combined with collagen crosslinking and intra-stromal corneal ring segments: a systematic review and meta-analysis.

PURPOSE: To compare the efficacy of phakic intra-ocular lenses in isolation or in combination with corneal crosslinking (CXL) and/or intra-stromal corneal ring segments (ICRS) in keratoconus. METHODS: Data extracted from the publications meeting the selection. The outcome parameters included mean pre- and post-operative uncorrected distance visual acuity, corrected distance visual acuity (CDVA), sphere and cylinder of refraction and complications. Available data analyzed with Cochrane Review Manager. RESULTS: A total of 23 studies including 464 eyes were included. All the parameters showed significant improvement in all subgroups other than CDVA in ACPIOL + CXL subgroup and cylinder in PIOL + CXL subgroups. There was not a significant difference between PCPIOL and ACPIOL in the outcomes, exception was more improvement of CDVA in "ACPIOL only" than" PCPIOL only" subgroup. CONCLUSION: Both PCPIOLs and ACPIOLs are comparably safe and efficient options in management of KCN and their efficacy significantly improves when combined with CXL/ICRS.

A portable, low-cost practice model for microsurgical skills training.

PURPOSE: We describe a portable practice model for acquisition of microsurgical skills using widely available inexpensive tools and materials as a model in learning ophthalmic corneal suturing skills. METHODS: Interested participants without prior microsurgery experience affiliated with the Jacobs School of Medicine and Biomedical Sciences with no prior microsurgical experience qualified to participate. Each participant completed written informed consent. We developed a 3-dimensional micro-stellated icosahedron model using microtubules, monofilament fishing line, jewelers' forceps, and a basic laboratory dissection microscope. We tested this model in improving microsurgical skills in a randomized, controlled intervention trial. Following a pre-assessment task of passing a microsurgical needle and performing a tie, participants were randomized to a control or an intervention (building the micro-stellated icosahedrons) group. The assessment task was repeated after two weeks. Videos of pre- and post-assessments were rated by two masked ophthalmologists. Technique scores and time to complete microsurgical tasks were analyzed to determine improvement in skills. RESULTS: A total of 27 microsurgically naïve participants were recruited and randomized (14 Intervention / 13 Control). Comparing pre- and post-assessments, the intervention group showed significant decrease in time required to pass the needle (P = 0.018) and significant improvement in technical scores. (P = 0.001). In the control group, there was no significant decrease in time or improvement in technical scores. CONCLUSIONS: The portable inexpensive micro-stellated icosahedron skills acquisition model is an effective practice model to acquire skills necessary to perform a microsurgical tie. The similarity in dimensions between the model and the eye suggests translatability to ophthalmic surgery.

Extrarenal Signs of Proximal Renal Tubular Acidosis Persist in Nonacidemic Nbce1b/c-Null Mice.

BACKGROUND: The SLC4A4 gene encodes electrogenic sodium bicarbonate cotransporter 1 (NBCe1). Inheritance of recessive mutations in SLC4A4 causes proximal renal tubular acidosis (pRTA), a disease characterized by metabolic acidosis, growth retardation, ocular abnormalities, and often dental abnormalities. Mouse models of pRTA exhibit acidemia, corneal edema, weak dental enamel, impacted colons, nutritional defects, and a general failure to thrive, rarely surviving beyond weaning. Alkali therapy remains the preferred treatment for pRTA, but it is unclear which nonrenal signs are secondary to acidemia and which are a direct consequence of NBCe1 loss from nonrenal sites (such as the eye and enamel organ) and therefore require separate therapy. SLC4A4 encodes three major NBCe1 variants: NBCe1-A, NBCe1-B, and NBCe1-C. NBCe1-A is expressed in proximal tubule epithelia; its dysfunction causes the plasma bicarbonate insufficiency that underlies acidemia. NBCe1-B and NBCe1-C exhibit a broad extra-proximal-tubular distribution. METHODS: To explore the consequences of Nbce1b/c loss in the absence of acidemia, we engineered a novel strain of Nbce1b/c-null mice and assessed them for signs of pRTA. RESULTS: Nbce1b/c-null mice have normal blood pH, but exhibit increased mortality, growth retardation, corneal edema, and tooth enamel defects. CONCLUSIONS: The correction of pRTA-related acidemia should not be considered a panacea for all signs of pRTA. The phenotype of Nbce1b/c-null mice highlights the physiologic importance of NBCe1 variants expressed beyond the proximal tubular epithelia and potential limitations of pH correction by alkali therapy in pRTA. It also suggests a novel genetic locus for corneal dystrophy and enamel hypomineralization without acidemia.

Posterior pole retinal thickness distribution pattern in keratoconus.

PURPOSE: To evaluate the pattern of retinal thickness distribution in patients with keratoconus (KCN) and its correlation with disease severity. METHODS: For this cross-sectional cohort study, the study subjects with documented keratoconus and normal eyes were prospectively enrolled. All subjects had anterior segment (Pentacam HR) and posterior segment (Spectralis) imaging. Posterior segment imaging by optical coherence tomography included the posterior pole asymmetry analysis map. Data were analyzed with multiple linear regression models and correlation tests to examine the mean and variance of the measured thickness of the retina and its distribution relative to the presence and severity of KCN. RESULTS: A total of 24 subjects with keratoconus (48 eyes) and 14 normal subjects (28 eyes) enrolled in this study. The posterior pole retinal thickness, both superior and inferior hemifields, as well as the overall retinal thickness in KCN patients was greater than the control group. There was a direct correlation between the overall retinal thickness of the posterior pole and the severity of KCN (R2 = 0.422, P < 0.001). However, the variability of the retinal thickness showed no difference between KCN-afflicted and healthy eyes. CONCLUSION: Although KCN is a disease of the anterior segment of the eye, we found an orderly increase in posterior pole retinal thickness that is correlated with the severity of disease in KCN eyes compared to control. These findings suggest that the retina may maintain some degree of plasticity to respond to the degraded optical system of the eye.

Effects of amantadine on corneal endothelium.

PURPOSE: An adverse effect of amantadine, a drug used for Parkinson's disease, is corneal edema. While corneal endothelial cell loss is noted with amantadine toxicity, the reversibility of corneal edema suggests that amantadine affects active mechanisms regulating corneal hydration. Although mainly known as a NMDA receptor antagonist, amantadine is also a K+-channel blocker. The purpose of this study was to investigate potential mechanisms of amantadine's toxic effects on corneal endothelium. METHODS: Bovine corneas were used for short-circuit current measurements of corneal endothelial active ion transport to compare the effects of amantadine with an NMDA receptor agonist (NMDA) and antagonist (D-APV), and the K+-channel blockers BaCl2 and clotrimazole. Cell death and changes in cell morphology were observed using annexin V stain, alizarin red S staining of the intercellular junctions, ZO-1 immunolocalization, and phalloidin stain of the actin cytoskeleton. RESULTS: Amantadine caused a transient decrease in the short-circuit current that mimicked the effect of clotrimazole. BaCl2, and the NMDA receptor agonist and antagonist had no effect on the short-circuit current. Tissue incubation with amantadine caused an increase in cell area (measured by ZO-1 localization) and cell height (measured by phalloidin stain) but did not increase apoptotic cell death (annexin V stain). CONCLUSIONS: The similarity of amantadine and clotrimazole effects on the short-circuit current and the effects on cell volume suggest that amantadine's actions on corneal endothelium are mediated via K+ channels. The observed absence of cell death and transient effect on short-circuit current support the reported reversibility of amantadine-induced corneal edema.

Insights into activity and inhibition from the crystal structure of human O-GlcNAcase.

O-GlcNAc hydrolase (OGA) catalyzes removal of ßα-linked N-acetyl-D-glucosamine from serine and threonine residues. We report crystal structures of Homo sapiens OGA catalytic domain in apo and inhibited states, revealing a flexible dimer that displays three unique conformations and is characterized by subdomain α-helix swapping. These results identify new structural features of the substrate-binding groove adjacent to the catalytic site and open new opportunities for structural, mechanistic and drug discovery activities.

I-Gel versus laryngeal mask airway (LMA) classic as a conduit for tracheal intubation using ventilating bougie.

BACKGROUND AND AIMS: Supraglottic airways (SGAs) are generally used for airway management; but can also be used as a conduit for tracheal intubation. Our primary aim was to evaluate i-Gel and laryngeal mask airway (LMA) classic as conduits for tracheal intubation using ventilating bougie by assessing number of attempts and time for insertion of SGAs, ventilating bougie and endotracheal tube (ETT), and total intubation time. MATERIAL AND METHODS: A randomized clinical trial was carried out in 58 patients requiring general anesthesia and endotracheal intubation for planned surgery. They were randomly divided into Group I and Group C. After induction of anesthesia, i-Gel was inserted in Group I and LMA Classic in Group C; ventilating bougie was passed through SGA followed by the removal of SGA and railroading of ETT over ventilating bougie. Parameters observed were number of attempts and time taken for device insertion, total intubation time, and hemodynamic variables. RESULTS: Twenty-nine patients were included in each group. First attempt success rate for SGA insertion (86.2% in Group I and 75.9% in Group C (P = 0.5)), ventilating bougie insertion (79.32% in Group I and 82.8% in Group C (P = 0.99)) and ETT insertion (100% in Group I and 96.5% in Group C) was not different in the two groups. Total intubation time was 93.3 ± 9.0 s in Group I and 108. 96 ± 16.5 s in Group C (P < 0.0001). CONCLUSIONS: i-Gel and LMA Classic both can be used as a conduit for tracheal intubation using ventilating bougie with stable hemodynamic parameters.

Structure-based design and development of (benz)imidazole pyridones as JAK1-selective kinase inhibitors.

The mammalian Janus Kinases (JAK1, JAK2, JAK3 and TYK2) are intracellular, non-receptor tyrosine kinases whose activities have been associated in the literature and the clinic with a variety of hyperproliferative diseases and immunological disorders. At the onset of the program, it was hypothesized that a JAK1 selective compound over JAK2 could lead to an improved therapeutic index relative to marketed non-selective JAK inhibitors by avoiding the clinical AEs, such as anemia, presumably associated with JAK2 inhibition. During the course of the JAK1 program, a number of diverse chemical scaffolds were identified from both uHTS campaigns and de novo scaffold design. As part of this effort, a (benz)imidazole scaffold evolved via a scaffold-hopping exercise from a mature chemical series. Concurrent crystallography-driven exploration of the ribose pocket and the solvent front led to analogs with optimized kinome and JAK1 selectivities over the JAK2 isoform by targeting several residues unique to JAK1, such as Arg-879 and Glu-966.

Tricyclic 1,5-naphthyridinone oxabicyclooctane-linked novel bacterial topoisomerase inhibitors as broad-spectrum antibacterial agents-SAR of left-hand-side moiety (Part-2).

Novel bacterial topoisomerase inhibitors (NBTIs) represent a new class of broad-spectrum antibacterial agents targeting bacterial Gyrase A and ParC and have potential utility in combating antibiotic resistance. A series of novel oxabicyclooctane-linked NBTIs with new tricyclic-1,5-naphthyridinone left hand side moieties have been described. Compounds with a (R)-hydroxy-1,5-naphthyridinone moiety (7) showed potent antibacterial activity (e.g., Staphylococcus aureus MIC 0.25 µg/mL), acceptable Gram-positive and Gram-negative spectrum with rapidly bactericidal activity. The compound 7 showed intravenous and oral efficacy (ED50) at 3.2 and 27 mg/kg doses, respectively, in a murine model of bacteremia. Most importantly they showed significant attenuation of functional hERG activity (IC50 >170 µM). In general, lower logD attenuated hERG activity but also reduced Gram-negative activity. The co-crystal structure of a hydroxy-tricyclic NBTI bound to a DNA-gyrase complex exhibited a binding mode that show enantiomeric preference for R isomer and explains the activity and SAR. The discovery, synthesis, SAR and X-ray crystal structure of the left-hand-side tricyclic 1,5-naphthyridinone based oxabicyclooctane linked NBTIs are described.

Structure of the bacterial deacetylase LpxC bound to the nucleotide reaction product reveals mechanisms of oxyanion stabilization and proton transfer.

The emergence of antibiotic-resistant strains of pathogenic bacteria is an increasing threat to global health that underscores an urgent need for an expanded antibacterial armamentarium. Gram-negative bacteria, such as Escherichia coli, have become increasingly important clinical pathogens with limited treatment options. This is due in part to their lipopolysaccharide (LPS) outer membrane components, which dually serve as endotoxins while also protecting Gram-negative bacteria from antibiotic entry. The LpxC enzyme catalyzes the committed step of LPS biosynthesis, making LpxC a promising target for new antibacterials. Here, we present the first structure of an LpxC enzyme in complex with the deacetylation reaction product, UDP-(3-O-(R-3-hydroxymyristoyl))-glucosamine. These studies provide valuable insight into recognition of substrates and products by LpxC and a platform for structure-guided drug discovery of broad spectrum Gram-negative antibiotics.

Characteristics of the low density corneal endothelial monolayer.

Corneal endothelial cells form a leaky barrier on the posterior surface of the cornea, allowing influx of nutrient-carrying aqueous humor through the paracellular space and efflux of excess fluid. Corneal edema arises when the density of these non-proliferative endothelial cells declines from endothelial disease or intraocular surgery. The cellular changes occurring at low densities are ill-defined. We therefore investigated the paracellular pathway of corneal endothelial cell monolayers of varying density to determine alterations occurring in paracellular permeability and monolayer morphology. Primary cultures of bovine corneal endothelial cells (BCECs) were passaged onto permeable supports under varying culture conditions to obtain confluent monolayers of <1000, 1000-1999 and >2000 cells/mm(2). Culture growth was monitored by transendothelial electrical resistance measurements. Diffusional permeability to sodium fluorescein, FITC-dextran MW 4000 or FITC-dextran MW 20,000 was measured. Confluent cultures were also analyzed by immunofluorescence localization of the tight junction protein ZO-1 and by transmission electron microscopy. For comparison, we evaluated ZO-1 for low and high density human corneal endothelium. Our results showed that all BCEC cultures grew to the same final transendothelial electrical resistance regardless of final density. In the diffusional permeability assay, permeability increased significantly only for the smallest tracer molecule (sodium fluorescein) in the lowest density monolayers (<1000 cells/mm(2)). ZO-1 immunofluorescence distinctly localized to intercellular junctions in high density BCEC cultures but had more diffuse localization at lower densities. Transmission electron microscopy imaging revealed cells with thinner cross-sectional profiles and longer overlapping intercellular processes at low density relative to high density cultures. Low density human corneal endothelium lacked the diffuse ZO-1 distribution seen in BCECs. Our data supports the hypothesis that barrier integrity is the primary function disrupted in low density corneal endothelial monolayers and contradicts the idea of a linear decline in barrier function with decreasing cell density.

Novel tetrahydropyran analogs as dipeptidyl peptidase IV inhibitors: Profile of clinical candidate (2R,3S,5R)-2- (2,5-difluorophenyl)-5-(4,6-dihydropyrrolo [3,4-c]pyrazol-5-(1H)-yl)tetrahydro-2H-pyran-3-amine (23) [corrected].

A series of novel tri-2,3,5-substituted tetrahydropyran analogs were synthesized and evaluated as inhibitors of dipeptidyl peptidase IV (DPP-4) for the treatment of type 2 diabetes. Optimization of the series provided inhibitors with good DPP-4 potency and selectivity over other peptidases (QPP, DPP8, and FAP). Compound 23, which is very potent, selective, efficacious in the diabetes PD model, and has an excellent pharmacokinetic profile, is selected as a clinical candidate.

Dietary pattern of schoolgoing adolescents in urban Baroda, India.

Diet plays a very important role in growth and development of adolescents, during which the development of healthy eating habits is of supreme importance. There is a dual burden of undernutrition and overnutrition in this age-group. The study assessed the food habits, food preferences, and dietary pattern of schoolgoing urban adolescents in Baroda, India. Both quantitative and qualitative methods were used in this study. A quantitative survey was carried out using a pre-tested self-administered structured questionnaire among 1,440 students from class 6 to 12 in 7 English medium and 23 Gujarati medium schools. Focus group discussions, 5 each with adolescent boys and girls, were held, along with 5 focus group discussions with teachers of Gujarati and English medium schools. Nearly 80% of adolescents had consumed regular food, like dal, rice, chapati, and vegetables, including green leafy vegetables. Nearly 50% of them had consumed chocolates, and about one-third consumed fast foods. Nearly 60% of adolescents had their breakfast daily while the remaining missed taking breakfast daily. Nearly one-third of adolescents were missing a meal once or twice a week. A large majority had consumed regular foods. However, more than half of them had consumed chocolates, soft drinks, and over one-third had taken fast foods.

Risk assessment of variant Creutzfeldt-Jakob disease in corneal transplantation.

Purpose: While corneal transplantation is known to have a potential risk of transmission of variant Creutzfeldt-Jacob Disease (vCJD), the magnitude of this risk has not been quantified. Observations: A case report is presented of a 73 year-old man with a penetrating keratoplasty graft from corneal tissue that was recalled after transplantation due to risk of vCJD because it was later discovered that the donor had traveled to the United Kingdom (UK). Probabilities of vCJD transmission were extrapolated using Creutzfeldt-Jacob Disease (CJD) mortality (incidence) rate, all-cause death rate, and rate of recovery for intended transplantation. Conclusions: An overestimate of the risk of transplanting a cornea infected with vCJD in 2018 was 1 in 940,000. The true risk of vCJD transmission would be even lower due to an incomplete infectivity rate. We conclude that the risk of transmission of latent vCJD by corneal transplantation from a donor who traveled to the UK from 1980 to 1996 is exceedingly low.

Selective effects of estradiol on human corneal endothelial cells.

In Fuchs endothelial corneal dystrophy (FECD), mitochondrial and oxidative stresses in corneal endothelial cells (HCEnCs) contribute to cell demise and disease progression. FECD is more common in women than men, but the basis for this observation is poorly understood. To understand the sex disparity in FECD prevalence, we studied the effects of the sex hormone 17-ß estradiol (E2) on growth, oxidative stress, and metabolism in primary cultures of HCEnCs grown under physiologic ([O2]2.5) and hyperoxic ([O2]A) conditions. We hypothesized that E2 would counter the damage of oxidative stress generated at [O2]A. HCEnCs were treated with or without E2 (10 nM) for 7-10 days under both conditions. Treatment with E2 did not significantly alter HCEnC density, viability, ROS levels, oxidative DNA damage, oxygen consumption rates, or extracellular acidification rates in either condition. E2 disrupted mitochondrial morphology in HCEnCs solely from female donors in the [O2]A condition. ATP levels were significantly higher at [O2]2.5 than at [O2]A in HCEnCs from female donors only, but were not affected by E2. Our findings demonstrate the resilience of HCEnCs against hyperoxic stress. The effects of hyperoxia and E2 on HCEnCs from female donors suggest cell sex-specific mechanisms of toxicity and hormonal influences.

Selective effects of estradiol on human corneal endothelial cells.

Fuchs endothelial corneal dystrophy (FECD) results from genetic and environmental factors triggering mitochondrial and oxidative stress in corneal endothelial cells (CEnCs) leading to CEnC death and corneal opacification. FECD is more common in women than men, but the basis for this observation is unknown. Because FECD is commonly diagnosed around the time of the menopausal transition in women when estrogen levels decrease precipitously, we studied the effects of the potent estrogen,17-ß estradiol (E2) on growth, oxidative stress, and metabolism in primary cultures of human CEnCs (HCEnCs) under conditions of physiologic 2.5% O 2 ([O 2 ] 2.5 ) and under hyperoxic stress ([O 2 ] A : room air + 5% CO 2 ). We hypothesized that E2 would counter the stresses of the hyperoxic environment in HCEnCs. HCEnCs were treated ± 10 nM E2 for 7-10 days at [O 2 ] 2.5 and [O 2 ] A followed by measurements of cell density, viability, reactive oxygen species (ROS), mitochondrial morphology, oxidative DNA damage, ATP levels, mitochondrial respiration (O 2 consumption rate [OCR]), and glycolysis (extracellular acidification rate [ECAR]). There were no significant changes in HCEnC density, viability, ROS levels, oxidative DNA damage, OCR, and ECAR in response to E2 under either O 2 condition. We found that E2 disrupted mitochondrial morphology in HCEnCs from female donors but not male donors at the [O 2 ] A condition. ATP levels were significantly higher at [O 2 ] 2.5 compared to [O 2 ] A in HCEnCs from female donors only, but were not affected by E2. Our findings demonstrate the overall resilience of primary HCEnCs against hyperoxic stress. The selective detrimental effects of hyperoxia and estradiol on HCEnCs from female but not male donors suggests mechanisms of toxicity based upon cell-sex in addition to hormonal environment.