Role of aquaporins in corneal healing post chemical injury

Mineralocorticoid receptor antagonism improves corneal integrity in a rat model of limbal stem cell deficiency

Limbal stem cell deficiency (LSCD) is a sight-threatening condition caused by the loss and/or dysfunction of limbal stem cells (LSCs), which are essential for corneal epithelial regeneration and homeostasis and are critical for maintaining corneal transparency. We have previously shown that specific inactivation of the endothelial mineralocorticoid receptor (MR) inhibits corneal neovascularization (CN) and that MR antagonists (MRA) improve corneal epithelial wound healing. This study investigated the therapeutic potential of MRA in LSCD and their mechanisms of action. Using a rat model of LSCD, systemic administration of spironolactone (SPL) or a more specific MRA, eplerenone, similarly reduced CN and corneal oedema, demonstrating MR-specific effects. SPL further limited inflammation, enhanced the corneal epithelial barrier, reduced corneal conjunctivalization and promoted nerve regeneration, highlighting its potential to improve corneal integrity. Transcriptomic analysis revealed that SPL upregulated genes associated with LSC maintenance (Tp63, Wnt6), corneal epithelial differentiation (Vdr, Fermt1, Ehf) and nerve regeneration (Sprr1a, Anxa1), while downregulating genes associated with angiogenesis (Kdr, Scube2), inflammation (Ccl2, Cxcl1) and fibrosis (Fbln1, Snai1). Conversely, transgenic rats overexpressing human NR3C2 encoding MR showed corneal epithelial irregularities and dysregulation of genes related to extracellular matrix remodeling and fibrosis (Matn3, Serpine2, Fmod, Bgn, Ddr2), angiogenesis (Nrp2, Scube1) and limbal cell function (Ifitm3). These findings demonstrate that activation of the MR pathway disrupts limbal and corneal homeostasis and that SPL effectively modulates critical mechanisms in LSCD, offering promising therapeutic potential to reduce CN and improve corneal epithelial barrier integrity.

Distinctive roles of aquaporins and novel therapeutic opportunities against cancer

Aquaporins (AQPs) are integral membrane proteins responsible for facilitating the transmembrane transport of water and small solutes. Their involvement in diverse physiological functions extends to pathological conditions, including cancer, positioning them as promising targets for anticancer therapy. Tumor cells, particularly those with high metastatic potential, exhibit elevated AQP expression, reinforcing their critical role in tumor biology. Emerging evidence highlights AQPs' involvement in key oncogenic processes such as cell migration, proliferation, and tumor-associated edema, suggesting their potential as novel therapeutic targets. Despite this, the development of selective and potent AQP inhibitors has proven challenging. Efforts to produce small-molecule AQP inhibitors have largely been unsuccessful. However, recent advancements include monoclonal human IgG antibodies targeting extracellular domains of aquaporin-4, offering new therapeutic strategies, particularly in glioblastoma, where AQP-4 is overexpressed. However, recent advancements include monoclonal human IgG antibodies targeting extracellular domains of aquaporin-4, offering new therapeutic strategies, particularly in glioblastoma, where AQP-4 is over expressed. These antibodies hold promise for selectively targeting and eradicating AQP-4-expressing cells in malignant brain tumors. This review discusses the critical role AQPs play in cancer, including their contributions to tumor cell proliferation, migration, angiogenesis, and edema formation. Additionally, we explore innovative therapeutic approaches, such as antibody-based interventions, and outline potential future research directions in AQP-targeted cancer therapies.

Effect of Anterior Chamber Air on Central Corneal Thickness in Human Donor Eyes

PURPOSE

The purpose of this study was to describe the effects of intracameral air on corneal edema.

METHODS

A laboratory investigation was performed on human donor corneas. Baseline pachymetry measurements through anterior segment optical coherence tomography and endothelial cell density were obtained for all corneas. Each pair of corneas was separated and randomly assigned to undergo air injection or Optisol-GS into a BIONIKO artificial anterior chamber for 5 minutes at physiologic intraocular pressure confirmed by digital palpation. Photographs were obtained immediately on connection of the cornea to the artificial anterior chamber and on completion of the 5 minutes of treatment, with anterior chamber air being exchanged for Optisol-GS. Pretreatment and posttreatment photographs were obtained. Immediately after treatment, pachymetry was again obtained on all corneas. Pachymetry data underwent statistical analysis.

RESULTS

Corneal pachymetry improved from 690.5 ± 126.6 to 576.1 ± 87.2 μm, yielding a 114.4 ± 50.4 μm improvement of pachymetry in the group with air injected into the anterior chamber. This was a significant improvement of pachymetry when compared with the group with Optisol-GS injected into the anterior chamber, which showed an improvement from 662.3 ± 126.5 to 613.5 ± 108.0 μm, yielding an improvement of 48.8 ± 34.3 μm.

CONCLUSIONS

Injection of air into the anterior chamber leads to a significant decrease in corneal pachymetry. We thereby propose that injecting air intracamerally is an effective intraoperative intervention when visualization is negatively affected by corneal edema.

Neurovascular unit, neuroinflammation and neurodegeneration markers in brain disorders

Neurovascular unit (NVU) inflammation via activation of glial cells and neuronal damage plays a critical role in neurodegenerative diseases. Though the exact mechanism of disease pathogenesis is not understood, certain biomarkers provide valuable insight into the disease pathogenesis, severity, progression and therapeutic efficacy. These markers can be used to assess pathophysiological status of brain cells including neurons, astrocytes, microglia, oligodendrocytes, specialized microvascular endothelial cells, pericytes, NVU, and blood-brain barrier (BBB) disruption. Damage or derangements in tight junction (TJ), adherens junction (AdJ), and gap junction (GJ) components of the BBB lead to increased permeability and neuroinflammation in various brain disorders including neurodegenerative disorders. Thus, neuroinflammatory markers can be evaluated in blood, cerebrospinal fluid (CSF), or brain tissues to determine neurological disease severity, progression, and therapeutic responsiveness. Chronic inflammation is common in age-related neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), and dementia. Neurotrauma/traumatic brain injury (TBI) also leads to acute and chronic neuroinflammatory responses. The expression of some markers may also be altered many years or even decades before the onset of neurodegenerative disorders. In this review, we discuss markers of neuroinflammation, and neurodegeneration associated with acute and chronic brain disorders, especially those associated with neurovascular pathologies. These biomarkers can be evaluated in CSF, or brain tissues. Neurofilament light (NfL), ubiquitin C-terminal hydrolase-L1 (UCHL1), glial fibrillary acidic protein (GFAP), Ionized calcium-binding adaptor molecule 1 (Iba-1), transmembrane protein 119 (TMEM119), aquaporin, endothelin-1, and platelet-derived growth factor receptor beta (PDGFRβ) are some important neuroinflammatory markers. Recent BBB-on-a-chip modeling offers promising potential for providing an in-depth understanding of brain disorders and neurotherapeutics. Integration of these markers in clinical practice could potentially enhance early diagnosis, monitor disease progression, and improve therapeutic outcomes.

Necrostatin-1 protects corneal epithelial cells by inhibiting the RIPK1/RIPK3/MLKL cascade in a benzalkonium chloride-induced model of necroptosis

PURPOSE

Benzalkonium chloride (BAC) is commonly used as a preservative in ophthalmic medications, despite its potential to induce chemical injury. Extensive research has demonstrated that BAC can lead to adverse effects, including injuries to the ocular surface. Our study aimed to elucidate the underlying mechanism of necroptosis induced by BAC.

METHODS

Human corneal epithelial (HCE) cells and mouse corneas were subjected to chemical injury, and the necrostatin-1 (Nec1) group was compared to the dimethylsulfoxide (DMSO) group. The extent of damage to HCE cells was assessed using CCK-8 and flow cytometry. Hematoxylin and eosin staining, as well as fluorescein sodium staining, were used to detect and characterize corneal injury. The activation of inflammatory cytokines and necroptosis-related proteins and genes was evaluated using Western blotting, immunofluorescence staining, and quantitative RT‒PCR.

RESULTS

In our study, the induction of necroptosis by a hypertonic solution was not observed. However, necroptosis was observed in HCE cells exposed to NaOH and BAC, which activated the receptor-interacting protein kinase 1 (RIPK1) - receptor-interacting protein kinase 3 (RIPK3) - mixed lineage kinase domain-like protein (MLKL) signaling pathway. In mouse corneal tissues, BAC could induce necroptosis and inflammation. The administration of Nec1 mitigated the inflammatory response and ocular surface damage caused by BAC-induced necroptosis in our experimental models. Furthermore, our in vivo experiments revealed that the severity of necroptosis was greater in the 3-day group than in the 7-day group.

CONCLUSIONS

Necroptosis plays a role in the pathological development of ocular surface injury caused by exposure to BAC. Furthermore, our study demonstrated that the administration of Nec1 could mitigate the pathological effects of necroptosis induced by BAC in clinical settings.

Cooperation of aquaporin 5 and the adrenergic system in the initiation of birth in rat model

Aquaporins (AQPs) are involved in the process of implantation, regulate myometrial contractions and cervical ripening, and maintain appropriate placental functioning. The molecular mechanism of these functions is not fully understood. Our study aimed to investigate the physiological significance of AQP5 during pregnancy and to determine the cooperation between the adrenergic system and the AQP5 in uterine contraction in the late-pregnant rat uterus. After administering AQP5 siRNA intraperitoneally to Sprague-Dawley rats, the length of the gestational period was determined and the changes in uterine contractions were measured in an isolated organ bath system. Pharmacological influence on AQP5 expression and uterine contraction was investigated by treatment with terbutaline (10 mg/kg, subcutaneously) and doxazosin (5 mg/kg, orally) in vivo; and mercuric chloride (HgCl2), in vitro. Moreover, the levels of cAMP response element binding protein (CREB) were measured in the uterus by an ELISA kit. The gestational period became shorter, AQP5 expression significantly decreased and rat uterus contraction increased after AQP5 siRNA treatment compared to the control. Treatment with terbutaline significantly increased AQP5 mRNA and protein expression after 30 min and continuously reduced it until 90 min, whereas doxazosin treatment did not significantly alter AQP5 expression. Treatment with the AQP5 antagonist HgCl2 increased spontaneous uterus contraction and decreased norepinephrine-induced uterus contraction with decreasing AQP5 expression in pregnant rat uterus. Moreover, the tocolytic effect through the adrenergic system was amplified in the presence of an AQP5 antagonist, presumably via the changes in cAMP level. In conclusion, our findings elucidate the collaborative role of aquaporin 5 (AQP5) and adrenergic systems in the regulation of uterine contractions in late-pregnant rats. Our findings suggest this may be a good starting point for developing a new tocolytic therapy.

Blast injury: Impact to the cornea

Visual disorders are common even after mild traumatic brain injury (mTBI) or blast exposure. The cost of blast-induced vision loss in civilians, military personnel, and veterans is significant. The visual consequences of blasts associated with TBI are elusive. Active military personnel and veterans report various ocular pathologies including corneal disorders post-combat blasts. The wars and conflicts in Afghanistan, Iraq, Syria, and Ukraine have significantly increased the number of corneal and other ocular disorders among military personnel and veterans. Binocular vision, visual fields, and other visual functions could be impaired following blast-mediated TBI. Blast-associated injuries can cause visual disturbances, binocular system problems, and visual loss. About 25% of veterans exposed to blasts report corneal injury. Blast exposure induces corneal edema, corneal opacity, increased corneal thickness, damage of corneal epithelium, corneal abrasions, and stromal and endothelial abnormality including altered endothelial density, immune cell infiltration, corneal neovascularization, Descemet membrane rupture, and increased pain mediators in animal models and the blast-exposed military personnel including veterans. Immune response exacerbates blast-induced ocular injury. TBI is associated with dry eyes and pain in veterans. Subjects exposed to blasts that cause TBI should undergo immediate clinical visual and ocular examinations. Delayed visual care may lead to progressive vision loss, lengthening/impairing rehabilitation and ultimately may lead to permanent vision problems and blindness. Open-field blast exposure could induce corneal injuries and immune responses in the cornea. Further studies are warranted to understand corneal pathology after blast exposure. A review of current advancements in blast-induced corneal injury will help elucidate novel targets for potential therapeutic options. This review discusses the impact of blast exposure-associated corneal disorders.

Tenascins and osteopontin in biological response in cornea

The structural composition, integrity and regular curvature of the cornea contribute to the maintenance of its transparency and vision. Disruption of its integrity caused by injury results in scarring, inflammation and neovascularization followed by losses in transparency. These sight compromising effects is caused by dysfunctional corneal resident cell responses induced by the wound healing process. Upregulation of growth factors/cytokines and neuropeptides affect development of aberrant behavior. These factors trigger keratocytes to first transform into activated fibroblasts and then to myofibroblasts. Myofibroblasts express extracellular matrix components for tissue repair and contract the tissue to facilitate wound closure. Proper remodeling following primary repair is critical for restoration of transparency and visual function. Extracellular matrix components contributing to the healing process are divided into two groups; a group of classical tissue structural components and matrix macromolecules that modulate cell behaviors/activities besides being integrated into the matrix structure. The latter components are designated as matricellular proteins. Their functionality is elicited through mechanisms which modulate the scaffold integrity, cell behaviors, activation/inactivation of either growth factors or cytoplasmic signaling regulation. We discuss here the functional roles of matricellular proteins in mediating injury-induced corneal tissue repair. The roles are described of major matricellular proteins, which include tenascin C, tenascin X and osteopontin. Focus is directed towards dealing with their roles in modulating individual activities of wound healing-related growth factors, e. g., transforming growth factor β (TGF β). Modulation of matricellular protein functions could encompass a potential novel strategy to improve the outcome of injury-induced corneal wound healing.