apyrase and Glaucoma

Topics: Adenosine Triphosphate; Animals; Antigens, CD; Apyrase; Disease Models, Animal; Female; Glaucoma; Intraocular Pressure; Male; Posterior Eye Segment

The cellular mechanisms linking elevated IOP with glaucomatous damage remain unresolved. Mechanical strains and short-term increases in IOP can trigger ATP release from retinal neurons and astrocytes, but the response to chronic IOP elevation is unknown. As excess extracellular ATP can increase inflammation and damage neurons, we asked if sustained IOP elevation was associated with a sustained increase in extracellular ATP in the posterior eye.. No ideal animal model of chronic glaucoma exists, so three different models were used. Tg-Myoc(Y437H) mice were examined at 40 weeks, while IOP was elevated in rats following injection of hypertonic saline into episcleral veins and in cynomolgus monkeys by laser photocoagulation of the trabecular meshwork. The ATP levels were measured using the luciferin-luciferase assay while levels of NTPDase1 were assessed using qPCR, immunoblots, and immunohistochemistry.. The ATP levels were elevated in the vitreal humor of rats, mice, and primates after a sustained period of IOP elevation. The ecto-ATPase NTPDase1 was elevated in optic nerve head astrocytes exposed to extracellular ATP for an extended period. NTPDase1 was also elevated in the retinal tissue of rats, mice, and primates, and in the optic nerve of rats, with chronic elevation in IOP.. A sustained elevation in extracellular ATP, and upregulation of NTPDase1, occurs in the posterior eye of rat, mouse, and primate models of chronic glaucoma. This suggests the elevation in extracellular ATP may be sustained in chronic glaucoma, and implies a role for altered purinergic signaling in the disease.

Topics: Adenosine Triphosphate; Animals; Antigens, CD; Apyrase; Cell Count; Chronic Disease; Disease Models, Animal; Female; Glaucoma; Immunoblotting; Immunohistochemistry; Intraocular Pressure; Macaca fascicularis; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Posterior Eye Segment; Rats; Rats, Inbred BN; Real-Time Polymerase Chain Reaction; Retinal Ganglion Cells; Signal Transduction

To investigate the mechanisms for endogenous production of extracellular adenosine in trabecular meshwork (TM) cells and evaluate its physiological relevance to the regulation of aqueous humor outflow facility.. Extra-cellular levels of adenosine monophosphate (AMP) and adenosine in porcine trabecular meshwork (PTM) cells treated with adenosine triphosphate (ATP), AMP, cAMP or forskolin with or without specific inhibitors of phosphodiesterases (IBMX) and CD73 (AMPCP) were determined by high-pressure liquid chromatography fluorometry. Extracellular adenosine was also evaluated in cell cultures subjected to cyclic mechanical stress (CMS) (20% stretching; 1 Hz) and after disruption of lipid rafts with methyl-β-cyclodextrin. Expression of CD39 and CD73 in porcine TM cells and tissue were examined by Q-PCR and Western blot. The effect of inhibition of CD73 on outflow facility was evaluated in perfused living mouse eyes.. PTM cells generated extracellular adenosine from extracellular ATP and AMP but not from extracellular cAMP. Increased intracellular cAMP mediated by forskolin led to a significant increase in extracellular adenosine production that was not prevented by IBMX. Inhibition of CD73 resulted, in all cases, in a significant decrease in extracellular adenosine. CMS induced a significant activation of extracellular adenosine production. Inhibition of CD73 activity with AMPCP in living mouse eyes resulted in a significant decrease in outflow facility.. These results support the concept that the extracellular adenosine pathway might play an important role in the homeostatic regulation of outflow resistance in the TM, and suggest a novel mechanism by which pathologic alteration of the TM, such as increased tissue rigidity, could lead to abnormal elevation of IOP in glaucoma.

Topics: 5'-Nucleotidase; Adenosine; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Antigens, CD; Apyrase; Aqueous Humor; Cells, Cultured; Cyclic AMP; Extracellular Space; Gene Expression Regulation, Enzymologic; Glaucoma; Intraocular Pressure; Membrane Microdomains; Mice; Mice, Inbred Strains; Stress, Mechanical; Swine; Trabecular Meshwork