title: Temperature oscillations drive cycles in the activity of MMP-2,9 secreted by a human trabecular meshwork cell line.
abstract: OBJECTIVE
  Aqueous humor inflow falls 50% during sleeping hours without proportional fall in IOP, partly reflecting reduced outflow facility. The mechanisms underlying outflow facility cycling are unknown. One outflow facility regulator is matrix metalloproteinase (MMP) release from trabecular meshwork (TM) cells. Because anterior segment temperature must oscillate due to core temperature cycling and eyelid closure during sleep, we tested whether physiologically relevant temperature oscillations drive cycles in the activity of secreted MMP.
  
  
  METHODS
  Temperature of transformed normal human TM cells (hTM5 line) was fixed or alternated 12 hours/12 hours between 33°C and 37°C. Activity of secreted MMP-2 and MMP-9 was measured by zymography, and gene expression by RT-PCR and quantitative PCR.
  
  
  RESULTS
  Raising temperature to 37°C increased, and lowering to 33°C reduced, activity of secreted MMP. Switching between 37°C and 33°C altered MMP-9 by 40% ± 3% and MMP-2 by 22% ± 2%. Peripheral circadian clocks did not mediate temperature-driven cycling of MMP secretion because MMP-release oscillations did not persist at constant temperature after 3 to 6 days of alternating temperatures, and temperature cycles did not entrain clock-gene expression in these cells. Furthermore, inhibiting heat shock transcription factor 1, which links temperature and peripheral clock-gene oscillations, inhibited MMP-9 but not MMP-2 temperature-driven MMP cycling. Inhibition of heat-sensitive TRPV1 channels altered total MMP secretion but not temperature-induced modulations. Inhibiting cold-sensitive TRPM-8 channels had no effect.
  
  
  CONCLUSIONS
  Physiologically relevant temperature oscillations drive fluctuations of secreted MMP-2 and MMP-9 activity in hTM5 cells independent of peripheral clock genes and temperature-sensitive TRP channels.
authors: Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Hong Kong.
authors: Stanley Ka-Lok
authors: SK
authors: Li
authors: Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States.
authors: Juni
authors: J
authors: Banerjee
authors: Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, United States.
authors: Christopher
authors: C
authors: Jang
authors: Department of Neuroscience, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States.
authors: Amita
authors: A
authors: Sehgal
authors: Department of Ophthalmology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States.
authors: Richard A
authors: RA
authors: Stone
authors: Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States.
authors: Mortimer M
authors: MM
authors: Civan
mesh_terms: D001831:Body Temperature / Q000235:genetics*; D002460:Cell Line; D002940:Circadian Rhythm / Q000502:physiology*; D005786:Gene Expression Regulation; D006801:Humans; D007429:Intraocular Pressure; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis / Q000235:genetics*; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis / Q000235:genetics*; D012313:RNA / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D014129:Trabecular Meshwork / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*
chemical_list: D012313:RNA; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9
keywords: circadian rhythm; matrix metalloproteinases; trabecular outflow
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