Cerebral vascular studies reveal potential new drug targets

Stroke causes many changes in gene activity in small blood vessels that are affected in the brain, and these changes could potentially be targeted with existing or future drugs to reduce brain injury or improve stroke recovery, according to a study led by Weill Cornell Medicine scientists.

In the study, which appeared April 14 in Proceedings of the National Academy of Sciences, the researchers conducted a comprehensive survey, in a preclinical model, of changes in gene activity in small blood vessels in the brain after stroke. Comparing these changes to those already noted in stroke patients, they cataloged hundreds of genes with significant stroke-driven changes and their possible relevance to human stroke.

“Our findings provide a knowledge base that enhances our understanding of stroke and point to specific molecules and pathways that can now be investigated as potential targets for future stroke treatments,” said study senior author Dr. Teresa Sanchez, assistant professor of pathology and laboratory medicine. and principal investigator from the Laboratory of Molecular and Translational Vascular Research at Weill Cornell Medicine. “There is also increasing recognition that vascular disease is associated with and contributes to cognitive dysfunction and dementia. This study has identified the molecular features associated with vascular dysfunction in the human brain after stroke, a major cause of dementia.”

Stroke has long been a leading cause of death and long-term disability worldwide. Most strokes are ischemic strokes involving blood clots in vessels serving the brain. Blockage or severe reduction in blood flow reduces the delivery of oxygen and nutrients to downstream brain cells, killing or injuring them and triggering inflammatory processes that can cause further damage.

Small cerebral blood vessels—or “cerebral microvasculature”—downstream of the occlusion are also affected, and changes in them are thought to contribute further to post-stroke brain damage. But these microvascular changes are technically challenging to record accurately, and so they haven’t been studied as well as other aspects of stroke — nor do they have specific treatments.

In the new study, Dr. Sanchez and his team, including first co-author Drs. Keri Callegari, Sabyasachi Dash and Hiroki Uchida, using a new, optimized method, recently published by the Sanchez lab at Nature Protocols, to study stroke-affected vessels to overcome this challenge. They comprehensively recorded post-stroke gene activity changes in the cerebral microvasculature in mice and identified changes that have also been seen in studies of human stroke patients.

Overall, the team found 541 genes whose activity was similarly altered in mouse and human cerebral microvessels after stroke. Dividing these genes into groups based on their functional roles and disease associations, they identified several main groups. This includes groups related to general inflammation, brain inflammation, vascular disease, and types of vascular dysfunction that would cause cerebral microvessels to become leaky. This leakage implies a weakening of the “blood-brain barrier,” the cellular lining of cerebral microvessels that protects the brain by keeping most of the circulating blood components out of it.

“We found that, after stroke, some molecules that would weaken the blood-brain barrier were upregulated, while others that should protect the blood-brain barrier were downregulated,” said Dr. Sanchez, who is also an assistant professor of neuroscience at the Feil Family Mind and Brain Research Institute. “This is consistent with clinical observations of impaired blood-brain barrier after stroke.”

The analysis also identified disturbances of the normal activity of genes that control sphingolipid levels. This fat-associated molecule is highly involved in regulating blood vessels, and disruption of its normal action has been observed in stroke, atherosclerosis, and vascular dementia. The team found that some of these sphingolipids were highly enriched in brain blood vessels compared to brain tissue. In addition, they identified changes to these sphingolipids in the cerebral microvasculature caused by stroke as well as changes to key molecules that control the levels of these lipids. These new findings will enable the pharmacological targeting of this pathway for stroke therapeutic discoveries.

The studies included assessments confirming the “medicinal potency,” or suitability for targeting with small molecule drugs, of many molecules with altered post-stroke production. Indeed, some of the identified molecules are already candidate drug targets for treating other pathological conditions, which may facilitate their reuse for the treatment of stroke and dementia.

Sanchez and his team are now following up with preclinical trials using candidate drugs or genetic methods to reverse some of the specific microvascular changes identified in their study, to investigate whether these could benefit stroke patients.

“We have produced this knowledge platform and we are using it, but we also hope that other scientists will join us in the effort to develop the first therapies targeting the microvasculature in stroke,” he said.