Cathepsin B and middle cerebral artery occlusion in the rat

Abstract

Lysosomal proteases, although tightly regulated under physiological conditions, are known to contribute to cell injury after various forms of tissue ischemia have occurred. Because cathepsin B is a prominent lysosomal protease found in brain parenchyma, the authors hypothesized that it may contribute to neuronal cell death after focal cerebral ischemia. The authors measured the expression and spatial distribution of cathepsin B within the ischemic brain in 43 animals by means of immunohistochemical analysis in a rat model of transient middle cerebral artery (MCA) occlusion. Cathepsin B activity was also measured within specific ischemic brain regions by using an in vitro assay (22 animals). In addition, the authors tested the therapeutic effect of preischemic intraventricular administration of stefin A, a cysteine protease inhibitor, on the volume of cerebral infarction after transient MCA occlusion (15 animals). Increased cathepsin B immunoreactivity was detected exclusively within the ischemic neurons after 2 hours of reperfusion following a 2-hour MCA occlusion. Cathepsin B immunolocalization in the ischemic region decreased by 24 hours of reperfusion, but then increased by 48 hours of reperfusion because the infarct was infiltrated by inflammatory cells. Increased immunolocalization of cathepsin B in the inflammatory cells located in the necrotic infarct core continued through 7 days of reperfusion. Cathepsin B enzymatic activity was significantly increased in the ischemic tissue at 2, 8, and 48 hours, but not at 24 hours of reperfusion after 2 hours of MCA occlusion. Continuous intraventricular infusion of stefin A, before 2 hours of MCA occlusion (15 animals), significantly reduced infarct volume compared with control animals (12 animals): the percentage of hemispheric infarct volume was 20+/-3.9 compared with 33+/-3.5 (standard error of the mean; p = 0.025). These data indicate that neuronal cathepsin B undergoes increased expression and activation within 2 hours of reperfusion after a 2-hour MCA occlusion and may be a mechanism contributing to neuronal cell death. Intraventricular infusion of stefin A, an inhibitor of cathepsin B, significantly reduces cerebral infarct volume in rats.

Effects of cathepsins B and L inhibition on postischemic protein alterations in the brain

“…Previously, we have shown that cathepsin B undergoes increased expression and activation in core neurons early after reperfusion following MCAO in the rat [11]. We now provide new data to show that the enzymatic activity of cathepsin B is elevated predominantly in the right subcortical region of the ischemic brain where the level of several ~66 kDa proteins were found to increase significantly after the ischemic insult.…”

“…Such a critical pathway is the rapid activation of cysteine proteases including the cathepsins, calpains, and caspases [4][5][6][7][8]. Cathepsins B and L contribute to cerebral injury after focal ischemia with reperfusion [9][10][11][12][13]. Previously, we demonstrated that CP-1, a non-toxic cysteine protease inhibitor which is relatively selective for cathepsins B and L, but not the calpains or caspases, is effective at reducing infarct volume and improving functional scores when administered intravenously to rats after 2 hours of MCAO and reperfusion [12].…”

Cortical Fluoro-Jade Staining and Blunted Adrenomedullary Response to Hypoglycemia after Noncoma Hypoglycemia in Rats

“…We did not detect labeled cells after hypoglycemic insult by using immunohistochemical probes of caspase and calpain pathways. However, these do not represent the only modes of neuron death as cathepsins are also implicated in neuron death, for example, after cerebral ischemia (Seyfried et al, 1997;Hill et al, 1997;Ü nal-Çevik et al, 2004). Because the number of dying cells is small in this model, it is not likely that methods for quantifying neuron loss (such as Nissl staining) will detect significant depletion of neurons.…”

Activation of Proinflammatory Caspases by Cathepsin B in Focal Cerebral Ischemia

“…The involvement of cathepsin B in ischemic cell death has been demonstrated in mild models of transient focal (Seyfried et al, 1997) and global (Hill et al, 1997;Kohda et al, 1996;Yamashima et al, 1998) ischemia, where the protease participates to reperfusion-associated damage. Our results show that cathepsin B is also released from lysosomes in acute focal ischemia, in the absence of reperfusion, suggesting that lysosomal destabilization is part of the primary events that lead to cerebral infarction.…”