Category Archives: Matrix Metalloproteinases (MMPs)

Curcumin Helps Suppress TNF-alpha and MMP-13 In Vitro


Induction of matrix metalloproteinase-13 gene expression by TNF-alpha is mediated by MAP kinases, AP-1, and NF-kappaB transcription factors in articular chondrocytes.

Tumor necrosis factor alpha (TNF-alpha), a major proinflammatory cytokine, induces arthritic joint inflammation and resorption of cartilage by matrix metalloproteinase-13 (MMP-13). RNA for MMP-13 is increased in human arthritic femoral cartilage. Mechanisms of this induction were investigated by pretreating primary human osteoarthritic (OA) femoral head chondrocytes or chondrosarcoma cells with the potential inhibitors of TNF-alpha signal transduction and downstream target transcription factors followed by stimulation with TNF-alpha and analysis of MMP-13 RNA/protein. TNF-alpha rapidly activated phosphorylation of extracellular signal-regulated kinases (ERKs), p38, and c-jun N-terminal kinase (JNK) mitogen-activated protein (MAP) kinases in human chondrocytes. Inhibitors of ERK (U0126, PD98059, and ERK1/2 antisense phosphorothioate oligonucleotide), JNK (SB203580, SP600125, and curcumin), and p38 (SB203580 and SB202190) pathways down-regulated the TNF-stimulated expression of MMP-13. Inhibitors of the transcription factors AP-1 (nordihydroguaiaretic acid, NDGA) and NF-kappaB (curcumin, proteasome inhibitors, and Bay-11-7085) suppressed TNF-alpha-induced MMP-13 expression in primary chondrocytes and SW1353 cells. These results suggest that induction of the MMP-13 gene by TNF-alpha is mediated by ERK, p38, and JNK MAP kinases as well as AP-1 and NF-kappaB transcription factors. Blockade of TNF-alpha signaling and its target transcription factors by the approaches tested here may be beneficial for reducing cartilage breakdown by MMP-13 in arthritis.

Liacini A, Sylvester J, Li WQ, Huang W…
Exp. Cell Res. Aug 2003
PMID: 12878172

Review: Homocysteine in Bone Remodeling


The role of homocysteine in bone remodeling.

Bone remodeling is a very complex process. Homocysteine (Hcy) is known to modulate this process via several known mechanisms such as increase in osteoclast activity, decrease in osteoblast activity and direct action of Hcy on bone matrix. Evidence from previous studies further support a detrimental effect on bone via decrease in bone blood flow and an increase in matrix metalloproteinases (MMPs) that degrade extracellular bone matrix. Hcy binds directly to extracellular matrix and reduces bone strength. There are several bone markers that can be used as parameters to determine how high levels of plasma Hcy (hyperhomocysteinemia, HHcy) affect bone such as: hydroxyproline, N-terminal collagen 1 telopeptides. Mitochondrion serves an important role in generating reactive oxygen species (ROS). Mitochondrial abnormalities have been identified during HHcy. The mechanism of Hcy-induced bone remodeling via the mitochondrial pathway is largely unknown. Therefore, we propose a mitochondrial mechanism by which Hcy can contribute to alter bone properties. This may occur both through generations of ROS that activate MMPs and could be extruded into matrix to degrade bone matrix. However, there are contrasting reports on whether Hcy affects bone density, with some reports in favour and others not. Earlier studies also found an alteration in bone biomechanical properties with deficiencies of vitamin B12, folate and HHcy conditions. Moreover, existing data opens speculation that folate and vitamin therapy act not only via Hcy-dependent pathways but also via Hcy-independent pathways. However, more studies are needed to clarify the mechanistic role of Hcy during bone diseases.

Vacek TP, Kalani A, Voor MJ, Tyagi SC…
Clin. Chem. Lab. Med. Mar 2013
PMID: 23449525

MMPs a Potential Target


Hydrogen sulfide and sodium nitroprusside compete to activate/deactivate MMPs in bone tissue homogenates.

Bone microvascular remodeling is the primary predictor of bone structure and function. Remodeling by its very nature implies synthesis and degradation of the extracellular matrix. Normally, 50% of total protein in the vessel wall is elastin. During remodeling, elastin is degraded by specialized matrix metalloproteinases (MMPs). Because the turnover of elastin is 1000-fold slower than that of collagen, most of the elastin is replaced by stiffer collagen. Stiffer vessels impose pressure on the aortic valve, causing regurgitation and increased pulse pressure. On the other hand, high MMP activity will cause vascular dilatation, leading to aneurysm. Therefore, balanced constitutive remodeling is necessary for adequate bone structure and function. Interestingly, collagen-degrading MMPs are involved in various pathological conditions, including osteoporosis, osteoarthritis, and cardiovascular disease.

Sodium nitroprusside is a nitric oxide donor that could potentially alter MMP activity via vasodilation in vivo, but can also produce peroxynitrite, which activates MMPs by combining with superoxide. Moreover, hydrogen sulfide is a known antioxidant as well as a vasodilator, and is also speculated to contribute directly to MMP activity. We hypothesized that hydrogen sulfide reduced activity of MMP in ex vivo bone tissue homogenates and that sodium nitroprusside would increase MMP activity in vitro.
We surgically removed the tibia and femur from anesthetized mice, and prepared bone tissue homogenates using a mortar and pestle, measured the protein concentration with a spectrophotometer, and detected MMP activity using gelatin gel zymography.
Our data showed increased MMP activity at a sodium nitroprusside concentration of 1 μM, and MMP activity increased exponentially. There was a decrease in MMP activity with increasing hydrogen sulfide, beginning at 16 μM (P < 0.01) and continuing to 40 μM. Moreover, sodium nitroprusside 3 μM was able to overcome the decrease in MMP activity that occurred with hydrogen sulfide 40 μM; this resulted in a more pronounced exponential increase in MMP activity.
There are several substances that can potentially be used to decrease MMP activity and to alleviate pathological remodeling by MMPs.

Vacek TP, Qipshidze N, Tyagi SC
Vasc Health Risk Manag 2013
PMID: 23658491 | Free Full Text