Dynamics of Distribution of Capillaries with Matrix Metalloproteinase-2 and Its Tissue Inhibitor in Rat Brain during Development of Experimental Hypertension

[The distribution of matrix metalloproteinases and their tissue inhibitors in the brain vascular bed exposed to chronic tobacco smoke]

AIM

To study the distribution of MMP-2 and MMP-9 and their inhibitors (TIMP-2 and TIMP-1 respectively) in the brain vascular bed of rats exposed to chronic tobacco smoke.

MATERIAL AND METHODS

Localization and expression of MMP-2, MMP-9, TIMP-2 and TIMP-1 in the pial branches (I-V order vessels), intracerebral arteries and capillaries of rats exposed to tobacco smoke were studied for 36 weeks. The level of enzymatic activity was assessed by the relative quantity of enzymopositive arteries and amount of fragments per 1 mm2 and rate of immunohistochemical reaction. Specific capillary density per mm2 of brain tissue and optical density of the immunohistochemical product were calculated.

RESULTS

MMP-2 and TIMP-2 were found in all segments of the arterial course in control animals. In rats exposed to tobacco smoking, the expression of MMP-2 increased only in intracerebral arteries and capillaries while TIMP-2 level decreased. MMP-9 and TIMP-1 were noted only in single vessels, mainly small pial and intracerebral arteries, in intact animals. In rats exposed to tobacco smoke, MMP-9 expression significantly increased in all segments of the arterial course whereas the increase in TIMP-1 was observed mainly in large pial arteries.

CONCLUSION

In physiological conditions, the dynamic balance between MMP-2 and TIMP-2 maintains basic tissue metabolism. Products of tobacco combustion are inductors of the inducible MMP-9 which promotes morphofunctional changes. The imbalance in MMP-9 - TIMP-1 system causes the degradation of extracellular matrix in different segments of the brain arterial course promoting the development of cerebral dysfunction.