Hypertension and the blood-brain barrier

Area of Science:

• Neurology
• Vascular Biology
• Pathology

Background:

• Acute hypertension induces alternating vasodilation and vasoconstriction in cerebral surface vessels.
• The role of these vascular caliber changes in malignant hypertension's degenerative vascular changes is not fully understood.
• Current understanding lacks definitive evidence on the necessity of these changes for malignant hypertension pathology.

Purpose of the Study:

• To investigate the effects of acute hypertension on cerebral vasculature and the blood-brain barrier.
• To determine the contribution of vascular caliber changes to the development of malignant hypertension.
• To characterize early morphologic changes associated with acute hypertensive lesions and cerebral edema.

Main Methods:

• Microscopic examination of cerebral surface vessels under acute hypertension.
• Assessment of blood-brain barrier integrity, including interendothelial tight junctions.
• Analysis of astrocytic foot processes and protein permeability in evolving cerebral edema.
• Comparison of acute hypertensive lesion locations with chronic hypertension-related microaneurysms.

Main Results:

• No ischemic or morphologic damage was observed in blood-brain barrier components; tight junctions remained intact.
• Early cerebral edema manifested as swelling of astrocytic foot processes, specifically in regions with abnormal protein permeability.
• Acute hypertensive lesions were located in the cortex, differing from the ganglionic location of microaneurysms in chronic human hypertension.
• Protein permeability changes did not necessarily correlate with brain water permeability changes influenced by sympathetic regulation.

Conclusions:

• Acute hypertension alters cerebral vessel caliber but preserves blood-brain barrier integrity.
• Early cerebral edema in acute hypertension is linked to astrocyte swelling and protein leakage, not direct vascular damage.
• The pathological mechanisms of acute and chronic hypertension-induced cerebral vascular changes differ in location and nature.