Solulin administration caused a down-regulation of the expression of inflammatory cytokines in the penumbra. In particular, TNF-α, IL-1β, and IL-6 were regulated. In addition, we observed that the expression of CD11B, a marker for microglia/macrophage activation, was also significantly reduced in Solulin-treated ischemic animals compared to untreated infarcted controls. GFAP, an astroglia marker, and MMP-9 were not regulated by Solulin. Solulin achieved a significant reduction in mean total infarct volumes (27.4%) with effective protection of both cerebral cortex (19%) and basal ganglia (12.6%). The overall reduction of infarct volumes does not suffice to explain the disparate decreases in expression of the various pro-inflammatory cytokines (IL 1β, 79%; TNF-α, 59%; IL-6, 47%).
Cerebral ischemia triggers a pathogenic cascade in which microglia are locally attracted and activated and express growth factors, chemokines, and regulatory inflammatory cytokines as mediators that attract mononuclear cells and granulocytes which further damage the ischemic brain tissue and its penumbra . The mainly proinflammatory cytokines TNF-α and IL-1β may induce migration of neutrophils and macrophages into the CNS . The up-regulation of both cytokines has often been demonstrated in transient and permanent MCAO which suggests that these cytokines play an important role in the inflammatory response associated with focal ischemia [20, 21].
TNF-α serves as a marker for activation of microglia and macrophages during cerebral ischemia and other inflammatory reactions as reported previously  and appears to mediate cell death. Consistently, it was demonstrated that the administration of TNF-α antibodies or TNF-α binding receptors led to a reduction of infarct volumes in experimental animal stroke models [23, 24]. Other studies, however, emphasize the neuroprotective potency of TNF-α with a role during repair and regeneration of brain tissue , making TNF-α another example of the time-dependent duality of certain inflammatory molecules, being destructive at the beginning while inducing an isochronic coordination of protective mechanisms. IL-1β expression, like TNF-α, seems to promote infarction progression in animal models of ischemic stroke . Clausen and collaborators demonstrated that IL-1β mRNA and TNF-α mRNA, and TNF-α protein are produced by CD11b+ microglia/macrophages in the penumbra as well as the core of brain infarction . CD11B is also expressed by immature dendritic cells of probably myeloid origin during neuroinflammation after brain infarction which may be associated with phagocytosis . Its downregulation might involve a decreased degradation reaction by dendritic cells and a decreased activation of microglia and macrophages post-infarction, in turn leading to a decreased expression of TNF-α and IL-1β. IL-6 mRNA is produced during inflammatory processes of the CNS  and is up-regulated after pMCAO in rats ; however, its role in both acute and chronic brain damage is still unclear . Whether its up-regulation is indicative of neuronal damage or neural regeneration is still uncertain .
There was no difference in expression of glial fibrillary acidic protein (GFAP), neither in infarcted nor in the unaffected hemispheres of both Solulin and control rats. GFAP is the principal intermediate filament in mature astrocytes and serves as a marker for reactive astrogliosis [30, 31] after nervous tissue injury. Since tissue evaluation was done 24 hrs after tMCAO, the postoperative time span appears too short for a significant activation/proliferation of astrocytes. Thus, an increased GFAP-expression was not anticipated in our study.
Matrix metalloproteinases (MMP) are proteases related to extracellular matrix breakdown  inducing neuronal damage, blood-brain-barrier (BBB) disruption and rarely intracerebral hemorrhage. Degradation of the basal lamina and tight junctions of cerebral blood vessels leads to BBB disruption followed by formation of cytotoxic as well as vasogenic brain edema and consecutive apoptosis of neurons and oligodendrocytes . MMPs might also play a role in abetting neutrophil and macrophage invasion . MMP-9 is not expressed in the CNS but seems to invade the brain together with leukocyte infiltration induced by focal ischemia [35, 36]. Together with platelet-derived growth factor CC , MMP-9 has been involved in BBB breakdown after stroke [35, 37].
As cerebral reperfusion in the current study was produced by removal of the occluding thread, it appears unlikely that anticoagulation is central to Solulin's ability to reduce infarct volumes. Rather, its anti-inflammatory and anti-apoptotic activities, mediated by its lectin-like domain [11, 12] and/or corresponding effects of APC  seem to be involved. Antibodies against HMGB1 have been found to ameliorate brain infarction induced by transient ischemia in rats, with inhibition of the expression of TNFα, but practically no effect on cerebral blood flow .
Nonetheless, there may also be a role for anticoagulation, as restoring blood flow may give rise to downstream displacement of material formed around the occluding suture. Solulin might also act to restore blood flow in the dependent microvasculature, which is likely to get clogged to some extent during the ischemia period and will not readily re-open once the occluding thread has been removed. This possibility is supported by the observation that Solulin, in the mouse photothrombotic model, was able to restore blood flow when administered 30 or 60 min post-occlusion . From a different perspective, anti-inflammatory effects of Solulin may contribute to its beneficial effects in the mouse photothrombotic model: When administered 60 min after photothrombotic occlusion, Solulin only transiently restored blood flow, but was still able to cause a significant reduction of infarct size 24 hrs later . Thus, anti-inflammatory and anticoagulant (profibrinolytic) effects of Solulin may act in concert. As inflammation is a powerful procoagulant/antifibrinolytic force , this profile would make Solulin a promising tool in the setting of acute cerebral ischemia.