Stroke Laboratory

Research Projects

Glial cell contributions to restoration of function following stroke

A project has recently been initiated investigating the responses of glial cells in the tissue surrounding areas of damage induced by stroke in the brain. Astrocytes in these regions become activated and produce a form of scar around the damaged tissue. We are investigating the proposal that processes, leading to the development of this scar, limit the ability of surviving nerve cells in the brain to adapt to the injury and restore neurological function. Using a stroke model, we are characterising initial interactions between astrocytes and microglia that are a likely trigger for the scar development, as well as downstream changes in the astrocytes. These changes provide potential targets for therapies that could promote functional recovery well after the onset of the stroke.  We are also developing a cell culture model that is showing good potential as a novel model for characterising microglial and astrocytic responses to injury.

Modulation of gene expression in astrocytes and microglia

This project is a collaboration with Dr Håkan Muyderman and Prof Robert Rush and is aimed at selectively manipulating gene expression in cerebral astrocytes and microglia using immunogenes (DNA linked to antibodies directed at surface receptors). Suitable target receptors on astrocytes and microglia have been identified. Alterations in gene expression have been produced in astrocytes and microglia in culture and in the brain. Investigations are currently underway to improve the efficiency of DNA delivery and also to compare this approach to alternative methods for modifying gene expression. The immunogene technique will be used in future studies to characterise both normal properties of astrocytes and microglia and the contributions of these cells to stroke.

Confocal Images of cells in normal rat brain showing immunolabelling for (A) the microglial marker CD11b and (B) GFP. (C) Merged image.
(D) Many microglia expressing GFP in a glial scar surrounding a region of experimental injury.  Scale bar: A-C 10µm; D 100µm.
(Images generated by Josephine Malmevik)

Mitochondrial glutathione and brain cell death

Glutathione is a major intracellular antioxidant. It is contained in separate pools in the cytoplasm and mitochondria. Synthesis occurs only in the cytoplasm. Although the major glutathione pool in the cytoplasm has been extensively studied, the role of mitochondrial glutathione has received much less attention, particularly in brain cells. To investigate mitochondrial glutathione in a major cell population from brain, we have established conditions to selectively manipulate the mitochondrial and cytoplasmic pools in astrocytes in culture. Mitochondrial glutathione depletion leads to a greater astrocytic death following exposure to some substances that accumulate under pathological conditions. This increased sensitivity of the cells is apparently due in part to an induction of a specific abnormal mitochondrial change that has also been implicated in cell death in stroke. Increasing the mitochondrial glutathione content provides protection against subsequent insults.
The uptake of glutathione into isolated brain mitochondria and in mitochondria within cultured astrocytes has also been characterised. Transport into brain mitochondria is apparently dependent on the size of the glutathione gradient across the inner mitochondrial membrane. The pattern of inhibition by other transportable anions suggests the involvement of a tricarboxylate carrier in the glutathione uptake. The properties of this glutathione transport are markedly different for those described by others for uptake of glutathione into liver or kidney mitochondria. In addition, in astrocytes in culture, the pattern of restoration following glutathione depletion from mitochondria indicates interactions between cytoplasmic and mitochondrial pools that are more complex than those predicted from the studies of isolated mitochondria.

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Updated June 28, 2011