UC Irvine

Microbial infections of the cornea (keratitis) cause an estimated 1 million cases of visual impairment and blindness worldwide each year. Treatment includes antimicrobial agents followed by corticosteroids to reduce inflammation and inhibit fibrosis. However, corticosteroids have undesirable side effects including increased intraocular pressure and risk for glaucoma. The Hv1 voltage-gated proton channel functions in the regulation of pH and NOX-mediated ROS production and has been implicated in cancer, ischemic stroke, CNS demyelination, traumatic brain injury and spinal cord injury and presents a target for therapeutic intervention. However, the role of this proton channel in ocular disease has not been examined. The immune response to invading microorganisms is characterized by recruitment of neutrophils to the site of infection which produce reactive oxygen species (ROS). Nevertheless, if produced in excess or prolonged periods of time, ROS can cause tissue damage. Using a recently discovered potent inhibitor of the Hv1 proton channel called Hv1 Inhibitor Flexible (HIF), we show that in PMA-, curdlan-, zymosan- and ΔpscD-stimulated murine bone marrow and human neutrophils, HIF inhibits ROS production in a dose-dependent manner. Our data also show that Hvcn1-/- mice, which lack the Hv1 voltage-gated proton channel, develop more severe corneal disease. However, we found that there was no difference in neutrophils and monocytes infiltration into the corneas, indicating that the inability of Hvcn1-/- mice to eliminate the bacteria is not due to a defect in cell migration and infiltration. Our results suggest that HIF targeting of the Hv1 voltage-gated proton channel together with antibiotics has a strong potential for treatment of microbial keratitis.