Faculty Directory

Joseph A. Bonanno

Professor/Dean

Joseph A. Bonanno

School of Optometry, IUB
OP 220

812-855-4440
jbonanno@indiana.edu

Curriculum Vitae

Education
  • O.D.–1981 / University of California, Berkeley
  • Ph.D.–1987 / University of California, Berkeley
Courses Taught
  • V501 & 502: Integrative Optometry, using a PBL clinical case format
  • V542 & V543: Systems Approach to Biomedical Sciences, Biochemistry
Biography

Dr. Joseph Bonanno received his B.A in Biology from the University of Pennsylvania (1975), M.S. in Molecular Biology, O.D. (1981), and Ph.D. in Physiological Optics (1987) from the University of California, Berkeley. Dr. Bonanno did his postdoctoral work at Louisiana State University Department of Ophthalmology (1987–88) and the University of California, Berkeley, Department of Physiology-Anatomy, 1988–89. He then joined the faculty at UC Berkeley School of Optometry in 1989 as Assistant Professor, where he attained the rank of professor in 1997. He joined the faculty of Indiana University School of Optometry in July 1998 as professor of optometry where he continues his research in corneal physiology and teaches biochemistry and physiology to the optometry students. He served as associate dean for research at the school from January 2005 to August 2007 when he was appointed associate dean for academic affairs and student administration. Dr. Bonanno is a fellow of the American Academy of Optometry, a member of the Association for Research in Vision and Ophthalmology, and a member of the American Physiological Society. Dr. Bonanno was appointed dean of the School of Optometry in October 2010.

Publications

View the most recent list of Dr. Bonanno's publications on

Research
Ongoing Projects
  • Identification and regulation of bicarbonate transport mechanisms
  • Evaluation of lactate: H+ cotransporters and interaction with HCO3- / carbonic anhydrase mediated buffering
  • Role of SLCA411 in in Corneal Endothelial function
  • Biology of soluble adenylyl cyclase in corneal endothelium and other eye tissues
  • Role of cAMP and calcium mediated signal transduction pathways in regulating ion and fluid transport
Corneal Endothelial Pump

Our goal is to understand the nature of the corneal “endothelial pump” and how it is regulated. The corneal endothelium is responsible for maintaining the hydration & transparency of the cornea. This function is essential for good vision since a defective endothelium will lead to corneal edema and reduced visual acuity. Devising rational medical treatments for endothelial dysfunction is needed to treat damaged or diseased corneas.

  1. We are identifying and characterizing ion transport mechanisms that are responsible for fluid secretion. We use combined physiological, molecular biology and biophysical approaches. See our latest publications for examples. Currently, our lab is focusing on the role of bicarbonate transport and carbonic anhydrase activities on lactic acid transport. The corneal epithelium and stromal cells are very glycolytic and produce lots of lactic acid. For every glucose molecule taken up by the cornea from the anterior chamber about 1.7 lactate molecules are produced. This creates an osmotic imbalance if the lactate is not efficiently removed. We have recently identified MCT 1, 2, and 4 (monocarboxylate transporters) in corneal endothelium. Lactate dependent proton fluxes are enhanced by the presence of bicarbonate and by carbonic anhydrase activity. Our hypothesis is that this facilitated lactate efflux is a significant contributor to the “endothelial pump”
  2. Corneal endothelial cells are lost during aging and this loss is accelerated in diseases like Fuchs Dystrophy and during eye banking. Preventing this loss could delay the need for corneal transplant and extend the time that donor corneas could be used for transplantation. Therefore, a second area of interest is protection of endothelial cells. We found that endothelial cells possess a HCO3--stimulated adenylyl cyclase called soluble AC (sAC). This enzyme appears to be responsible for basal levels of [cAMP] in the cells. The [cAMP] can also be increased by adenosine through A2b receptors. We now know that cAMP signaling is protective.
  3. Increases in cAMP can also enhance the “endothelial pump”. The mechanism is uncertain, however we do know that the increased cAMP will activate the chloride channel CFTR and also increases the total endothelial electrical resistance or barrier function due to promotion of enhanced cell-to-cell adhesions
  4. Corneal endothelial cell loss during aging and in Fuchs’ Dystrophy is by apoptosis stimulated by oxidative stress. We have found that hypoxia preconditioning can protect cells from oxidative stress. This may be useful during surgical procedures
  5. CHED (Corneal hereditary endothelial dystrophy) and Fuchs’ Dystrophy are associated with mutations in the gene SLC4A11, which codes for a putative bicarbonate or borate transporter. The role of borate in cell biology is uncertain, but may be protective or promote cell proliferation. We are now studying these possible functions
endothelial transport model

Endothelial Transport Model. Model for Lactate:H+ transendothelial flux facilitated by 1Na+:2HCO3- cotransport, Na+/H+ exchange, and carbonic anhydrase activity. Lactate (13.5 mM)2 and protons produced by the corneal epithelium and keratocytes are taken up on the basolateral (stromal) membrane by MCT1 and MCT4. Local supply of extracellular H+ is assured by the presence of CO2 and the membrane carbonic anhydrase CA12. 1Na+:2HCO3- cotransport (NBCe1) together with cytosolic CAII and Na+/H+ exchange (NHE1) buffer the H+ influx and prevent a buildup of [H+] that will slow lactate:H+ cotransport. At the apical membrane, MCT2 moves lactate:H+ to the apical surface & aqueous humor ([lactate]= 7.5 mM2). The presence of HCO3- and CAIV consumes the protons again avoiding a proton buildup within the apical unstirred layer that would slow further lactate:H+ cotransport. Anion channels CFTR & CaCC (Calcium activated chloride channel) can also provide HCO3- at the apical surface to aid buffering. The transmembrane movement of lactate couples water movement through the MCTs themselves, or is driven osmotically via AQP1 and the plasma membrane. [Although many transporters are present only on the lateral membrane, for clarity we have distributed them throughout the basolateral domain in this cartoon.]

Hypoxia Preconditioning

Mild forms of stress (e.g., ischemia, hypoxia, growth factor deprivation, oxidative stress) that do not reach the threshold for damaging cells can often be used as a preconditioning treatment that will protect cells from more intense damaging stress relative to cells that did not receive the preconditioning. We have found that hypoxia preconditioning will protect corneal keratocytes (and epithelial cells) from UV radiation. Typically cells that are exposed to two minutes of broad spectrum UV show high rates of apoptosis (80%), but cells that were preconditioned with 6 hours of 0.5% O2, show only 15% apoptosis. Our hypothesis is that hypoxia activates at least two signal transduction pathways: HIF1α; (Hypoxia Inducible Factor 1a) and NFKB. NFKB activation acts to reduce the tumor suppressor PTEN leading to increased activity of the PI-3K signal transduction pathway and Akt (Protein kinase B). Akt phosphorylates and stabilizes HIF1α, which binds to HREs (hypoxia response elements) leading to expression and production of growth factors. Autocrine and paracrine activation of growth factor receptors stimulate RAS-MAPK and/or PI-3K pathways forming a positive feedback loop.

bovine keratocytes

Cultured bovine keratocytes were exposed to normal air/5%CO2 incubation or 1.5%/5%CO2 for 6 hours. Cells were then exposed to normal conditions for 2 hours and then irradiated with UV for 8 minutes. Live-Dead staining was done 6 hours later. A-C: Control keratocytes A, DAPI: B, Live calcein; C, Dead ethidium homodimer. D-F Hypoxia preconditioned keratocytes. D, DAPI; E, Live; F, Dead. Bar graph summarizes Live-Dead staining.

Corneal Oxygenation
phosphorescence quenching

Sufficient oxygen delivery to the cornea through contact lenses is important for maintaining corneal health and good vision. In the mid 1990’s we developed a non-invasive Phosphorescence Quenching technique for measuring tear oxygen under Rigid Gas Permeable lenses fit to rabbits. A few years later, this technique was adapted to use in humans.

A Palladium-Porphyrin dye complexed with Serum Albumin is coated onto hydrogel contact lenses. They are placed on the eye and the dye is excited by a flash of 540 nm light using a slit-lamp microscope. At high oxygen tension the phosphorescence decays very rapidly, while at low oxygen tension it decays slowly. Using this method we have determined the oxygen tension under several types of ydrogels under open and closed eye conditions. The recent papers provide details of the technique, data, and conclusions.