title: Dose- and time-dependent effects of actomyosin inhibition on live mouse outflow resistance and aqueous drainage tissues.
abstract: Actomyosin contractility modulates outflow resistance of the aqueous drainage tissues and intraocular pressure, a key pathogenic factor of glaucoma. We established methodology to reliably analyze the effect of latrunculin-B (Lat-B)-induced actin depolymerization on outflow physiology in live mice. A voltage-controlled microperfusion system for delivering drugs and simultaneously analyzing outflow resistance was tested in live C57BL/6 mice. Flow rate and perfusion pressure were reproducible within a coefficient of variation of 2%. Outflow facility for phosphate-buffered saline (0.0027 ± 0.00036 μL/min/mmHg; mean ± SD) and 0.02% ethanol perfusions (Lat-B vehicle; 0.0023 ± 0.0005 μL/min/mmHg) were similar and stable over 2 hours (p > 0.1 for change), indicating absence of a 'washout' artifact seen in larger mammals. Outflow resistance changed in graded fashion, decreasing dose- and time-dependently over 2 hours for Lat-B doses of 2.5 μM (p = 0.29), 5 μM (p = 0.039) and 10 μM (p = 0.001). Resulting outflow resistance was about 10 times lower with 10 μM Lat-B than vehicle control. The filamentous actin network was decreased and structurally altered in the ciliary muscle (46 ± 5.6%) and trabecular meshwork (37 ± 8.3%) of treated eyes relative to vehicle controls (p < 0.005; 5 μM Lat-B). Mouse actomyosin contractile mechanisms are important to modulating aqueous outflow resistance, mirroring mechanisms in primates. We describe approaches to reliably probe these mechanisms in vivo.
authors.affiliation: Doheny Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
authors.forename: MinHee K
authors.initials: MK
authors.lastname: Ko
authors.affiliation: Doheny Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
authors.forename: Eun Kyoung
authors.initials: EK
authors.lastname: Kim
authors.affiliation: Doheny Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Gonzalez
authors.affiliation: Doheny Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Tan
mesh_terms: D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism*; D000818:Animals; D000867:Anterior Chamber / Q000187:drug effects / Q000502:physiology; D001082:Aqueous Humor / Q000378:metabolism*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000008:administration & dosage / Q000494:pharmacology; D007429:Intraocular Pressure / Q000187:drug effects; D051379:Mice; D055503:Protein Multimerization / Q000187:drug effects; D053778:Thiazolidines / Q000008:administration & dosage / Q000494:pharmacology; D013997:Time Factors
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D053778:Thiazolidines; D000205:Actomyosin; C037068:latrunculin B