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Expression of matrix metalloproteinase 2 and heat shock protein-72 in immobilized muscle in rats
E Carmeli1, T G Haimovitch, C E Nemcovsky
1Department of Physical Therapy, Sackler Faculty of Medicine, Stanley Steyer School of Health Professions, Tel Aviv University, Ramit Aviv, Israel. elie@post.tau.ac.il
Abstract:
Metalloproteinases (MMPs) are proteolytic enzymes that function in the extracellular matrix to degrade connective tissues. While it is clear that certain induced skeletal muscle pathologies promote increased expression of MMP-2 and heat shock protein- 72 (HSP-72), the relationship between muscle disuse and expression of MMP-2 and HSP-72 in muscles is unknown. These experiments tested the hypothesis that knee immobilization induced expression of MMP-2 and HSP-72 is disuse-dependent in a way that short-term joint immobilization increases HSP-72 expression, whereas long-term joint immobilization increases MMP-2 expression in skeletal muscles. Male rats (8 months old) completed 1, 2, 3, and 4 weeks of knee joint immobilization. Muscle mRNA and protein levels of MMP-2 and HSP-72 were assessed in Gastrocnemius (Gast), Superficial and Deep Quadriceps, and Soleus (Sol) muscles by reverse transcriptase-polymerase chain reaction and western blotting, respectively. Results reveal that during the first two weeks of immobilization there is increased protein levels of HSP-72 and expression of mRNA of HSP-72 mainly in slow twitch muscle fibers. However, 3 and 4 weeks of joint immobilization increased both mRNA and protein levels of MMP-2 in skeletal muscles containing a high percentage of fast type II fibers (i.e., Gast and superficial quadriceps). These results support the hypothesis that different periods of muscle disuse induced different proteins expression, and that the influence of joint immobilization on the expression of HSP-72 in the short-term, and MMP-2 in the long ran is associated to fiber types.
Insights
Muscle disuse affects protein expression differently over time. Short-term immobilization increases heat shock protein-72 (HSP-72), while long-term immobilization elevates matrix metalloproteinase-2 (MMP-2) in skeletal muscles.
Area of Science:
- Muscle physiology and molecular biology
- Extracellular matrix remodeling
- Skeletal muscle adaptation
Background:
- Matrix metalloproteinases (MMPs) degrade connective tissue.
- Heat shock protein-72 (HSP-72) is involved in cellular stress responses.
- Previous studies linked muscle pathologies to MMP-2 and HSP-72 expression, but disuse effects were unknown.
Purpose of the Study:
- To investigate the relationship between muscle disuse and the expression of MMP-2 and HSP-72.
- To test the hypothesis that immobilization-induced MMP-2 and HSP-72 expression is disuse-dependent.
- To determine if short-term vs. long-term immobilization differentially affects these protein expressions.
Main Methods:
- Male rats underwent knee joint immobilization for 1, 2, 3, and 4 weeks.
- Muscle samples (Gastrocnemius, Quadriceps, Soleus) were analyzed for MMP-2 and HSP-72 mRNA and protein levels.
- Techniques included reverse transcriptase-polymerase chain reaction and western blotting.
Main Results:
- Short-term immobilization (1-2 weeks) increased HSP-72 protein and mRNA, primarily in slow-twitch muscle fibers.
- Long-term immobilization (3-4 weeks) elevated both MMP-2 mRNA and protein levels, particularly in fast type II fiber-rich muscles.
- Differential expression patterns were observed between slow-twitch and fast-twitch muscle fibers.
Conclusions:
- Muscle disuse duration influences the expression of specific proteins in skeletal muscle.
- Short-term immobilization upregulates HSP-72, while long-term immobilization upregulates MMP-2.
- The observed effects are associated with muscle fiber type composition, suggesting distinct adaptive responses to disuse.