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Clusterin Seals the Ocular Surface Barrier in Mouse Dry Eye.

Bauskar A, Mack WJ, Mauris J, Argüeso P, Heur M, Nagel BA, Kolar GR, Gleave ME, Nakamura T, Kinoshita S, Moradian-Oldak J, Panjwani N, Pflugfelder SC, Wilson MR, Fini ME, Jeong S - PLoS ONE (2015)

Bottom Line: When the CLU level drops below the critical all-or-none threshold, the barrier becomes vulnerable to desiccating stress.CLU binds selectively to the ocular surface subjected to desiccating stress in vivo, and in vitro to the galectin LGALS3, a key barrier component.Positioned in this way, CLU not only physically seals the ocular surface barrier, but it also protects the barrier cells and prevents further damage to barrier structure.

View Article: PubMed Central - PubMed

Affiliation: USC Institute for Genetic Medicine and Graduate Program in Medical Biology, Keck School of Medicine of USC, University of Southern California, Los Angeles, California, United States of America.

ABSTRACT
Dry eye is a common disorder caused by inadequate hydration of the ocular surface that results in disruption of barrier function. The homeostatic protein clusterin (CLU) is prominent at fluid-tissue interfaces throughout the body. CLU levels are reduced at the ocular surface in human inflammatory disorders that manifest as severe dry eye, as well as in a preclinical mouse model for desiccating stress that mimics dry eye. Using this mouse model, we show here that CLU prevents and ameliorates ocular surface barrier disruption by a remarkable sealing mechanism dependent on attainment of a critical all-or-none concentration. When the CLU level drops below the critical all-or-none threshold, the barrier becomes vulnerable to desiccating stress. CLU binds selectively to the ocular surface subjected to desiccating stress in vivo, and in vitro to the galectin LGALS3, a key barrier component. Positioned in this way, CLU not only physically seals the ocular surface barrier, but it also protects the barrier cells and prevents further damage to barrier structure. These findings define a fundamentally new mechanism for ocular surface protection and suggest CLU as a biotherapeutic for dry eye.

No MeSH data available.


Related in: MedlinePlus

Topical CLU ameliorates pre-existing ocular surface barrier disruption caused by desiccating stress.(Left). The standard desiccating stress (DS) protocol was applied for 5-days to create ocular surface disruption. Non-stressed (NS) mice housed under normal ambient conditions served as a baseline control. (Left) After the indicated time period, barrier disruption was confirmed by measuring corneal epithelial uptake of fluorescein (FU = Fluorescence Units at 521 nm) in a subset of mice. Values are expressed as the mean ± SD. *p<0.0001 (n = 4). (Right) The same desiccating stress (DS) protocol was continued for another 5 days while eyes with desiccating stress were treated topically with 1 uL of recombinant human CLU (rhCLU) formulated in PBS at 2 ug/mL, or with PBS control, 4 times/day. The fluorescein uptake test was then performed on these remaining mice. Values are expressed as the mean ± SD. *p<0.0001(n = 4).
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pone.0138958.g003: Topical CLU ameliorates pre-existing ocular surface barrier disruption caused by desiccating stress.(Left). The standard desiccating stress (DS) protocol was applied for 5-days to create ocular surface disruption. Non-stressed (NS) mice housed under normal ambient conditions served as a baseline control. (Left) After the indicated time period, barrier disruption was confirmed by measuring corneal epithelial uptake of fluorescein (FU = Fluorescence Units at 521 nm) in a subset of mice. Values are expressed as the mean ± SD. *p<0.0001 (n = 4). (Right) The same desiccating stress (DS) protocol was continued for another 5 days while eyes with desiccating stress were treated topically with 1 uL of recombinant human CLU (rhCLU) formulated in PBS at 2 ug/mL, or with PBS control, 4 times/day. The fluorescein uptake test was then performed on these remaining mice. Values are expressed as the mean ± SD. *p<0.0001(n = 4).

Mentions: Having clearly demonstrated the preventive effect of CLU in protecting the ocular surface against desiccating stress, we next assessed the potential of CLU to ameliorate pre-existing ocular surface disruption. Representative results are shown in Fig 3. In this experiment, we applied the 5-day desiccating stress protocol, and then treated topically with rhCLU at 2 ug/mL (4 times/day) for another 5 days while maintaining the same desiccating stress protocol. Following this, barrier integrity was assayed. The PBS control showed a high level of dye uptake, ~12X greater than NS controls, but the barrier was essentially intact in CLU treated mice, similar to NS controls.


Clusterin Seals the Ocular Surface Barrier in Mouse Dry Eye.

Bauskar A, Mack WJ, Mauris J, Argüeso P, Heur M, Nagel BA, Kolar GR, Gleave ME, Nakamura T, Kinoshita S, Moradian-Oldak J, Panjwani N, Pflugfelder SC, Wilson MR, Fini ME, Jeong S - PLoS ONE (2015)

Topical CLU ameliorates pre-existing ocular surface barrier disruption caused by desiccating stress.(Left). The standard desiccating stress (DS) protocol was applied for 5-days to create ocular surface disruption. Non-stressed (NS) mice housed under normal ambient conditions served as a baseline control. (Left) After the indicated time period, barrier disruption was confirmed by measuring corneal epithelial uptake of fluorescein (FU = Fluorescence Units at 521 nm) in a subset of mice. Values are expressed as the mean ± SD. *p<0.0001 (n = 4). (Right) The same desiccating stress (DS) protocol was continued for another 5 days while eyes with desiccating stress were treated topically with 1 uL of recombinant human CLU (rhCLU) formulated in PBS at 2 ug/mL, or with PBS control, 4 times/day. The fluorescein uptake test was then performed on these remaining mice. Values are expressed as the mean ± SD. *p<0.0001(n = 4).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4581869&req=5

pone.0138958.g003: Topical CLU ameliorates pre-existing ocular surface barrier disruption caused by desiccating stress.(Left). The standard desiccating stress (DS) protocol was applied for 5-days to create ocular surface disruption. Non-stressed (NS) mice housed under normal ambient conditions served as a baseline control. (Left) After the indicated time period, barrier disruption was confirmed by measuring corneal epithelial uptake of fluorescein (FU = Fluorescence Units at 521 nm) in a subset of mice. Values are expressed as the mean ± SD. *p<0.0001 (n = 4). (Right) The same desiccating stress (DS) protocol was continued for another 5 days while eyes with desiccating stress were treated topically with 1 uL of recombinant human CLU (rhCLU) formulated in PBS at 2 ug/mL, or with PBS control, 4 times/day. The fluorescein uptake test was then performed on these remaining mice. Values are expressed as the mean ± SD. *p<0.0001(n = 4).
Mentions: Having clearly demonstrated the preventive effect of CLU in protecting the ocular surface against desiccating stress, we next assessed the potential of CLU to ameliorate pre-existing ocular surface disruption. Representative results are shown in Fig 3. In this experiment, we applied the 5-day desiccating stress protocol, and then treated topically with rhCLU at 2 ug/mL (4 times/day) for another 5 days while maintaining the same desiccating stress protocol. Following this, barrier integrity was assayed. The PBS control showed a high level of dye uptake, ~12X greater than NS controls, but the barrier was essentially intact in CLU treated mice, similar to NS controls.

Bottom Line: When the CLU level drops below the critical all-or-none threshold, the barrier becomes vulnerable to desiccating stress.CLU binds selectively to the ocular surface subjected to desiccating stress in vivo, and in vitro to the galectin LGALS3, a key barrier component.Positioned in this way, CLU not only physically seals the ocular surface barrier, but it also protects the barrier cells and prevents further damage to barrier structure.

View Article: PubMed Central - PubMed

Affiliation: USC Institute for Genetic Medicine and Graduate Program in Medical Biology, Keck School of Medicine of USC, University of Southern California, Los Angeles, California, United States of America.

ABSTRACT
Dry eye is a common disorder caused by inadequate hydration of the ocular surface that results in disruption of barrier function. The homeostatic protein clusterin (CLU) is prominent at fluid-tissue interfaces throughout the body. CLU levels are reduced at the ocular surface in human inflammatory disorders that manifest as severe dry eye, as well as in a preclinical mouse model for desiccating stress that mimics dry eye. Using this mouse model, we show here that CLU prevents and ameliorates ocular surface barrier disruption by a remarkable sealing mechanism dependent on attainment of a critical all-or-none concentration. When the CLU level drops below the critical all-or-none threshold, the barrier becomes vulnerable to desiccating stress. CLU binds selectively to the ocular surface subjected to desiccating stress in vivo, and in vitro to the galectin LGALS3, a key barrier component. Positioned in this way, CLU not only physically seals the ocular surface barrier, but it also protects the barrier cells and prevents further damage to barrier structure. These findings define a fundamentally new mechanism for ocular surface protection and suggest CLU as a biotherapeutic for dry eye.

No MeSH data available.


Related in: MedlinePlus