Lactate treatment causes NF-kappaB activation and CD44 shedding in cultured trabecular meshwork cells

• Published in: Investigative ophthalmology & visual science Vol. 48; no. 4; pp. 1615 - 1621
• Main Authors: Miller, Adam M, Nolan, Michael J, Choi, John, Koga, Tomoyo, Shen, Xiang, Yue, Beatrice Y J T, Knepper, Paul A
• Format: Journal Article
• Language: English
• Published: United States 01-04-2007
• Subjects: Adult; Blotting, Western; Cell Survival; Cells, Cultured; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Humans; Hyaluronan Receptors - metabolism; Lactic Acid - pharmacology; Matrix Metalloproteinase 14 - metabolism; Middle Aged; Time Factors; Trabecular Meshwork - drug effects; Trabecular Meshwork - metabolism; Transcription Factor RelA - metabolism
• ISSN: 0146-0404

To challenge human trabecular meshwork (TM) cells using lactate to mimic cell stress and observe the effects on cell viability, NF-kappaB, and membrane type 1 matrix metalloproteinase (MT1-MMP) expression and the ectodomain shedding of soluble (s)CD44.
Human TM cells grown in 10% fetal calf serum (FCS) were incubated in 0.1% FCS with 1, 10, or 40 mM lactate or PBS for 5 and 30 minutes and 1, 3, and 6 hours. Cell viability was determined with trypan blue staining. NF-kappaB and MT1-MMP expression was evaluated through Western blot analysis of medium and the cytoplasmic and nuclear fractions. Media sCD44 concentration was determined by enzyme-linked immunosorbent assay and Western blot analysis.
The TM cell viability was significantly decreased after incubation for 3 hours with 40 mM lactate (P < 0.01) and 6 hours with 10 and 40 mM lactate (P < 0.001). Western blot analysis showed an increased NF-kappaB p50 and MT1-MMP expression and activity by 5 minutes in lactate-treated TM cells compared with that of control cells. At 6 hours, NF-kappaB p65 was increased in nuclear fraction of lactate-treated compared with control cells. Treatment with 1 mM lactate caused an increase in the media concentration of both the 32 and 55 kDa sCD44 at 3 (P < 0.05) and 6 hours (P < 0.01).
Lactate treatment resulted in dose- and time-dependent effects on human TM cell viability, translocation of NF-kappaB, and activation of MT1-MMP. Increased shedding of sCD44 occurred with the l mM dose of lactate. Lactate treatment of human TM cells in culture offers a useful cell model to examine the stress responses that occur in glaucoma.