calpain and Calcinosis

Topics: Actins; Animals; Calcinosis; Calcium; Calpain; Cataract; Collagen; Fibrosis; Heterozygote; Lens, Crystalline; Macrophages; Mice; Mice, Inbred C57BL; TRPM Cation Channels

Age-associated central arterial wall stiffness is linked to extracellular matrix remodeling, including fibrosis and vascular calcification. Angiotensin II induces both matrix metalloproteinase 2 (MMP2) and calpain-1 expression and activity in the arterial wall. However, the role of calpain-1 in MMP2 activation and extracellular matrix remodeling remains unknown. Dual histo-immunolabeling demonstrates colocalization of calpain-1 and MMP2 within old rat vascular smooth muscle cells. Overexpression of calpain-1 induces MMP2 transcripts, protein levels, and activity, in part, by increasing the ratio of membrane type 1 MMPs to tissue inhibitor of metalloproteinases 2. These effects of calpain-1 overexpression-induced MMP2 activation are linked to increased collagen I and III production and vascular calcification. In addition, overexpression of calpain-1 also induces transforming growth factor-β1/Smad signaling, elastin degradation, alkaline phosphatase activation, and total calcium content but reduces the expression of calcification inhibitors, osteopontin, and osteonectin, in cultured vascular smooth muscle cells in vitro and in carotid artery rings ex vivo. Furthermore, both calpain-1 and collagen II increase with aging within human aortic intima. Interestingly, in aged human aortic wall, both calpain-1 and collagen II are highly expressed in artherosclerotic plaque areas compared with grossly normal areas. Cross-talk of 2 proteases, calpain-1 and MMP2, leads to secretion of active MMP2, which modulates extracellular matrix remodeling via enhancing collagen production and facilitating vascular calcification. These results establish calpain-1 as a novel molecular candidate to retard age-associated extracellular matrix remodeling and its attendant risk for hypertension and atherosclerosis.

Topics: Adolescent; Aged; Aging; Animals; Aorta; Blotting, Western; Calcinosis; Calpain; Cells, Cultured; Collagen; Elastin; Enzyme Activation; Fibrosis; Humans; Male; Matrix Metalloproteinase 2; Middle Aged; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Rats; Rats, Inbred BN; Rats, Inbred F344; Reverse Transcriptase Polymerase Chain Reaction; Tissue Inhibitor of Metalloproteinase-2; Young Adult

Glaucoma is a neurodegenerative disease in which elevated intraocular pressure (IOP) leads to progressive loss of retinal ganglion cells (RGCs) and blindness. Calcium dyshomeostasis has been suggested to play a role in the pathologic events that lead to RGC loss, though the details of these events are not well understood. Calcium-induced activation of calpain has been shown to contribute to neuronal death in a wide variety of neurodegenerative diseases. The authors hypothesize that similar events occur in glaucoma.. The authors used a well-established rat model of experimental glaucoma. Retinal tissues were harvested after 5 or 10 days of elevated IOP and were subjected to immunoblot analysis, immunoprecipitation, and MALDI-ProTOF/MS peptide fingerprint mapping. Immunohistochemistry was used to localize calpain activation.. The authors present four independent lines of evidence that calpain is activated in experimental glaucoma. First, they showed that a 55-kDa autocatalytic active form of calpain is detected on immunoblot analysis. Second, they demonstrated the cleavage of two well-established calpain substrates, spectrin and calcineurin, only in eyes with elevated IOP. Third, they used MALDI-ProTOF to analyze cleaved calcineurin and immunoblot analysis of spectrin cleavage products and showed that both substrates were cleaved by calpain in experimental glaucoma. Fourth, they used immunohistochemistry to show that calpain-mediated spectrin cleavage occurs in RGCs under conditions of elevated IOP.. These data support the hypothesis that calpain is activated under conditions of elevated intraocular pressure and provide further details of the pathologic events leading to RGC loss in glaucoma.

Topics: Animals; Blotting, Western; Calcinosis; Calpain; Disease Models, Animal; Enzyme Activation; Glaucoma; Immunoenzyme Techniques; Immunoprecipitation; Intraocular Pressure; Male; Proteomics; Rats; Rats, Inbred BN; Retinal Ganglion Cells; Spectrin; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization