Calpain inhibitors reduce retinal hypoxia in ischemic retinopathy by improving neovascular architecture and functional perfusion.
In ischemic retinopathies, underlying hypoxia drives abnormal neovascularization that damages retina and causes blindness. The abnormal neovasculature is tortuous and leaky and fails to alleviate hypoxia, resulting in more pathological neovascularization and retinal damage. With an established model of ischemic retinopathy we found that calpain inhibitors, when administered in moderation, reduced architectural abnormalities, reduced vascular leakage, and most importantly reduced retinal hypoxia. Mechanistically, these calpain inhibitors improved stability and organization of the actin cytoskeleton in retinal endothelial cells undergoing capillary morphogenesis in vitro, and they similarly improved organization of actin cables within new blood vessels in vivo. Hypoxia induced calpain activity in retinal endothelial cells and severely disrupted the actin cytoskeleton, whereas calpain inhibitors preserved actin cables under hypoxic conditions. Collectively, these findings support the hypothesis that hyper-activation of calpains by hypoxia contributes to disruption of the retinal endothelial cell cytoskeleton, resulting in formation of neovessels that are defective both architecturally and functionally. Modest suppression of calpain activity with calpain inhibitors restores cytoskeletal architecture and promotes formation of a functional neovasculature, thereby reducing underlying hypoxia. In sharp contrast to "anti-angiogenesis" strategies that cannot restore normoxia and may aggravate hypoxia, the therapeutic strategy described here does not inhibit neovascularization. Instead, by improving the function of neovascularization to reduce underlying hypoxia, moderate calpain inhibition offers a method for alleviating retinal ischemia, thereby suggesting a new treatment paradigm based on improvement rather than inhibition of new blood vessel growth.
Hoang
Mien V
MV
Department of Pathology and Center for Vascular Biology Research, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA.
Smith
Lois E H
LE
Senger
Donald R
DR
D000199:Actins / Q000378:metabolism; D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D020134:Catalytic Domain / Q000187:drug effects; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D003599:Cytoskeleton / Q000187:drug effects / Q000473:pathology; D042783:Endothelial Cells / Q000187:drug effects / Q000473:pathology; D006023:Glycoproteins / Q000494:pharmacology / Q000627:therapeutic use*; D006801:Humans; D000860:Hypoxia / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D012160:Retina / Q000166:cytology / Q000187:drug effects / Q000473:pathology*; D012164:Retinal Diseases / Q000188:drug therapy* / Q000473:pathology; D015861:Retinal Neovascularization / Q000188:drug therapy* / Q000473:pathology; D012171:Retinal Vessels / Q000187:drug effects / Q000473:pathology
D000199:Actins; D015853:Cysteine Proteinase Inhibitors; D006023:Glycoproteins; C039304:calpain inhibitors; D002154:Calpain
Physiol Rev. 2003 Jul;83(3):731-801
12843408
Angiogenesis. 1999;3(1):9-14
14517440
Surv Ophthalmol. 2008 Mar-Apr;53(2):150-63
18348880
J Biol Chem. 1989 Nov 15;264(32):18866-9
2553724
Trends Cell Biol. 2002 Jan;12(1):46-54
11854009
Invest Ophthalmol Vis Sci. 2006 Dec;47(12):5469-75
17122138
J Biol Chem. 2001 Dec 21;276(51):48382-8
11602605
Proc Natl Acad Sci U S A. 1995 Jan 31;92(3):905-9
7846076
FASEB J. 2006 Jul;20(9):1443-51
16816119
Mol Med. 1995 Jan;1(2):182-93
8529097
FEBS Lett. 1999 Oct 22;460(1):17-22
10571053
Proc Natl Acad Sci U S A. 1996 May 14;93(10):4851-6
8643492
Nature. 2005 Dec 15;438(7070):960-6
16355161
Nat Med. 2007 Jul;13(7):868-873
17589522
J Biol Chem. 2003 Jan 3;278(1):327-34
12399469
Microvasc Res. 1993 Sep;46(2):135-42
7504160
Angiogenesis. 2007;10(2):133-40
17332988
Methods Mol Biol. 2000;144:245-59
10818770
Bioorg Med Chem Lett. 2000 Oct 2;10(19):2187-91
11012026
Proc Natl Acad Sci U S A. 2004 Feb 17;101(7):1874-9
14769914
PLoS One. 2008;3(11):e3554
18978936
J Cell Biol. 1998 May 4;141(3):647-62
9566966
Arch Ophthalmol. 1996 Jan;114(1):66-71
8540853
J Biol Chem. 2004 May 14;279(20):20775-85
14988399
Arch Ophthalmol. 2003 Apr;121(4):547-57
12695252
Circ Res. 2006 Mar 17;98(5):617-25
16484616
Am J Physiol. 1998 Sep;275(3):L461-8
9728040
Diabetes. 2004 Feb;53 Suppl 1:S12-8
14749260
J Cell Sci. 2002 Sep 1;115(Pt 17):3415-25
12154072
Thromb Res. 2001 May 15;102(4):353-61
11369428
J Biol Chem. 1999 Jul 23;274(30):21265-75
10409684
Proc Natl Acad Sci U S A. 1996 Jun 25;93(13):6687-92
8692879
Invest Ophthalmol Vis Sci. 1994 Jan;35(1):101-11
7507904
Curr Med Chem. 2000 Dec;7(12):1171-88
11032966
Methods Mol Biol. 2005;294:269-85
15576918
J Cell Sci. 2005 Sep 1;118(Pt 17):3829-38
16129881
Bioorg Med Chem Lett. 2005 Jun 2;15(11):2857-60
15911268
Lab Invest. 2007 Mar;87(3):227-30
17259997
Lab Invest. 1995 Jun;72(6):638-45
7540233
Mol Cell Biol. 2000 Jun;20(12):4474-81
10825211
J Biol Chem. 1997 Dec 26;272(52):32719-22
9407041