Mast Cell Stabilization Reduces Hemorrhage Formation and Mortality After Administration of Thrombolytics in Experimental Ischemic Stroke

Abstract

Background-Thrombolysis with tissue plasminogen activator (tPA) improves stroke outcome, but hemorrhagic complications and reperfusion injury occasionally impede favorable prognosis after vessel recanalization. Perivascularly located cerebral mast cells (MCs) release on degranulation potent vasoactive, proteolytic, and fibrinolytic substances. We previously found MCs to increase ischemic and hemorrhagic brain edema and neutrophil accumulation. This study examined the role of MCs in tPA-mediated hemorrhage formation (HF) and reperfusion injury. Methods and Results-Exposure to tPA in vitro induced strong MC degranulation. In vivo experiments in a focal cerebral ischemia/reperfusion model in rats showed 70-to 100-fold increase in HF after postischemic tPA administration (PϽ0.001). Pharmacological MC stabilization with cromoglycate led to significant reduction in tPA-mediated HF at 3 (97%), 6 (76%), and 24 hours (96%) compared with controls (PϽ0.01, PϽ0.001, and PϽ0.01, respectively). Furthermore, genetically modified MC-deficient rats showed similarly robust reduction of tPA-mediated HF at 6 (92%) and 24 (89%) hours compared with wild-type littermates (PϽ0.01 and PϽ0.001, respectively). MC stabilization and MC deficiency also significantly reduced other hallmarks of reperfusion injury, such as brain swelling and neutrophil infiltration. These effects of cromoglycate and MC deficiency translated into significantly better neurological outcome (PϽ0.01 and PϽ0.05, respectively) and lower mortality (PϽ0.05 and PϽ0.05, respectively) after 24 hours. Conclusions-MCs appear to play an important role in HF and reperfusion injury after tPA administration. Pharmacological stabilization of MCs could offer a novel type of therapy to improve the safety of administration of thrombolytics.

Thrombin-dependent intravascular leukocyte trafficking regulated by fibrin and the platelet receptors GPIb and PAR4

“…In addition, rt-PA has been shown to increase tissue injury and enhance neutrophil tissue infiltration following ischaemiareperfusion injury to the brain 60 , lung 61 and kidneys 62 . The known proinflammatory function of recombinant t-PA has been partly attributed to its direct activating effects on the endothelium and inflammatory cells, as well as through the generation of fibrin degradation products 63 and plasmin 64 .…”

Hypothermia in cardiogenic shock reduces systemic t-PA release

“…Although t-PA is important in keeping vessel walls free from thrombi under physiologic circumstances, it has been found to have proinflammatory properties that could contribute to reperfusion injury [15,14,42,43]. In this experiment, cardiogenic shock was found to increase the anti-inflammatory TGF-1 and pro-inflammatory IL-6, to a similar degree in both groups.…”

“…It is synthesized and stored in endothelial cells and vascular neurons [7,8], and is released in response to ischemia and other injurious stimuli [9][10][11][12][13]. Interestingly, t-PA has also been found to have proinflammatory properties that could contribute to tissue injury in ischemia-reperfusion injury [14,15].…”

Mild hypothermia markedly reduces ischemia related coronary t-PA release

“…t-PA is known to induce matrix degradation via activation of matrix metallopeptidase 9, and increase oxidative stress and inflammation via upregulation of inducible nitric oxide synthase [43,44]. Furthermore, it is associated with activation and degranulation of mast cells with subsequent proinflammatory effects [27]. t-PA has also been shown to increase release of norepinephrine from sympathetic neurons and thereby contribute to cardiac arrythmias in ischemia/reperfusion [45].…”

“…The molecular basis for reperfusion damage has not been fully elucidated, but there is evidence for several possible mechanisms of damage including oxidative stress, calcium overload, mitochondrial damage, complement activation and an inflammatory reaction [21][22][23][24][25][26]. Interestingly, t-PA has been found to have proinflammatory properties that could contribute to reperfusion injury [27,28].…”