Inhibition of Leukotriene B₄Action Mitigates Intracerebral Hemorrhage-Associated Pathological Events in Mice

Abstract

Infiltration of neutrophils has been suggested to play an important role in the pathogenesis of intracerebral hemorrhage (ICH) for which effective therapeutic interventions remain unavailable. In the present study we focused on leukotriene B (LTB) as a potent chemotactic factor for neutrophils in order to address its contribution to the pathologic events associated with ICH. ICH with hematoma expansion into the internal capsule that resulted in severe sensorimotor dysfunction was induced by injection of collagenase in mouse striatum. We found that LTB as well as mRNAs of 5-lipoxygenase (5-LOX) and 5-LOX-activating protein were increased in the brain after ICH. Daily treatment with a 5-LOX inhibitor zileuton (3 or 10 mg/kg, i.v.) prevented ICH-induced increase in LTB, attenuated neutrophil infiltration into the hematoma, and ameliorated sensorimotor dysfunction. In addition, mice deficient in LTB receptor BLT exhibited a lower number of infiltrating neutrophils in the hematoma and lower levels of sensorimotor dysfunction after ICH than did wild-type mice. Similarly, daily treatment of mice with BLT antagonist ONO-4057 (30 or 100 mg/kg, by mouth) from 3 hours after induction of ICH inhibited neutrophil infiltration and ameliorated sensorimotor dysfunction. ONO-4057 also attenuated inflammatory responses of microglia/macrophages in the perihematoma region and axon injury in the internal capsule. These results identify LTB as a critical factor that plays a major role in the pathogenic events in ICH, and BLT is proposed as a promising target for ICH therapy.

N‐acetylcysteine targets 5 lipoxygenase‐derived, toxic lipids and can synergize with prostaglandin E2 to inhibit ferroptosis and improve outcomes following hemorrhagic stroke in mice

“…Methods for detecting incorporation of reactive lipids downstream of ALOX5 in vivo are not currently available, suggesting that other biomarkers will need to be developed as a proxy for NAC's ability to decrease ALOX5‐derived reactive lipids. Nevertheless, previous studies have shown that zileuton can improve functional recovery following ICH in mice …”

“…Fifth, forced expression of GST isoform (GSTA 4 ), known to neutralize reactive lipids in a glutathione-dependent manner, also prevented hemin-induced toxicity in vitro ( Fig 6G). 36 Stoichiometric antioxidants, such as vitamin E or cerovive (NXY-059), have been disappointing in the clinic for stroke treatment, likely because the concentrations required for these agents to be effective are relatively high compared to therapeutic agents that work catalytically. Seventh, increases in ALOX5 and ALOX5 AP message are observed in mice, rats, and humans; NAC treatment decreased hemin-induced ALOX5 gene expression and hemin-induced oxidized lipid species (Fig 5).…”

“…Nevertheless, previous studies have shown that zileuton can improve functional recovery following ICH in mice. 36 Stoichiometric antioxidants, such as vitamin E or cerovive (NXY-059), have been disappointing in the clinic for stroke treatment, likely because the concentrations required for these agents to be effective are relatively high compared to therapeutic agents that work catalytically. NAC also appears to act stoichiometrically to increase glutathione and is used at relatively high concentrations in vitro and in vivo (Fig 1).…”

Early and Sustained Increases in Leukotriene B4 Levels Are Associated with Poor Clinical Outcome in Ischemic Stroke Patients

“…Interestingly, a more recent study demonstrated that both BLT 1 and BLT 2 were rapidly upregulated after intracerebral hemorrhage (ICH) but BLT 1 was upregulated to a greater extent. Moreover, when BLT 1 knockout were compared to wild-type mice, substantially reduced neutrophil infiltration was observed in the former with no significant change in hematoma volume [42]. Unfortunately, BLT 2 knockout mice were not investigated.…”

Intracerebral Hemorrhage as an Axonal Tract Injury Disorder with Inflammatory Reactions

“…28) Indeed, we recently obtained evidence for the involvement of LTB 4 in the pathogenesis of ICH in the internal capsule, such that blockade of LTB 4 receptor attenuated neutrophil infiltration, axonal tract damage and neurological dysfunction in mice. 29) …”