Matrix metalloproteinases in brain injury

Area of Science:

• Biochemistry
• Neuroscience
• Molecular Biology

Background:

• Proteolytic remodeling of the extracellular matrix is crucial in development and pathological conditions like arthritis and tumor metastasis.
• Matrix metalloproteinases (MMPs) and plasminogen activators are key enzymes involved in extracellular matrix degradation.
• The blood-brain barrier can be compromised by specific enzymes like 72-kDa type IV collagenase (gelatinase A) and 92-kDa type IV collagenase (gelatinase B).

Purpose of the Study:

• To investigate the role of specific proteolytic enzymes in blood-brain barrier disruption during brain injury.
• To understand the molecular mechanisms, including gene regulation, underlying the production of these enzymes.
• To identify potential therapeutic targets and windows for treating secondary brain edema.

Main Methods:

• Analysis of gene expression and protein production of MMPs and plasminogen activators in response to brain injury models.
• Investigation of the regulatory elements, such as the phorbol ester responsive region (TRE) and AP-1 binding proteins, in the gelatinase B gene.
• Correlating the timing of enzyme production with the onset of blood-brain barrier opening and edema formation.

Main Results:

• Intracerebral injection of gelatinase A opens the blood-brain barrier.
• Endogenous production of gelatinase B, a late effector gene, occurs 16-24 hours after hemorrhagic brain injury or cytokine injection.
• Urokinase-type plasminogen activator (uPA) is co-produced with gelatinases, working together to degrade basement membranes and open the blood-brain barrier.
• This process contributes to secondary vasogenic brain edema after ischemic and hemorrhagic brain injury.

Conclusions:

• Proteolytic cascade enzymes, including MMPs and plasminogen activators, play a significant role in opening the blood-brain barrier and causing secondary brain edema.
• The delayed production of these enzymes creates a therapeutic window for intervention.
• Interfering with the genes encoding MMPs or inhibiting their activity presents potential treatment strategies for brain injury complications.