Interleukin-1 and Ischemic Brain Injury in the Newborn: Development of a Small Molecule Inhibitor of IL-1 Receptor

Inflammation that contributes to acute cerebrovascular disease is driven by the proinflammatory cytokine interleukin-1 and is known to exacerbate resulting injury. The activity of interleukin-1 is regulated by multimolecular protein complexes called inflammasomes. There are multiple potential inflammasomes activated in diverse diseases, yet the nature of the inflammasomes involved in brain injury is currently unknown. Here, using a rodent model of stroke, we show that the NLRC4 (NLR family, CARD domain containing 4) and AIM2 (absent in melanoma 2) inflammasomes contribute to brain injury. We also show that acute ischemic brain injury is regulated by mechanisms that require ASC (apoptosis-associated speck-like protein containing a CARD), a common adaptor protein for several inflammasomes, and that the NLRP3 (NLR family, pyrin domain containing 3) inflammasome is not involved in this process. These discoveries identify the NLRC4 and AIM2 inflammasomes as potential therapeutic targets for stroke and provide new insights into how the inflammatory response is regulated after an acute injury to the brain.

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Reduced Ischemic Brain Injury in Interleukin-1β Converting Enzyme—Deficient Mice

Journal of Cerebral Blood Flow & Metabolism ◽

10.1097/00004647-199802000-00009 ◽

1998 ◽

Vol 18 (2) ◽

pp. 180-185 ◽

Cited By ~ 230

Author(s):

Gerald P. Schielke ◽

Guo-Yuan Yang ◽

Brenda D. Shivers ◽

A. Lorris Betz

Keyword(s):

Brain Injury ◽

Cerebral Ischemia ◽

Focal Cerebral Ischemia ◽

Interleukin 1 ◽

Active Form ◽

Brain Lesion ◽

Biologically Active ◽

Ischemic Brain Injury ◽

Converting Enzyme ◽

Ischemic Brain

A variety of recent studies suggest a role for both inflammatory cytokines such as interleukin-1 beta (IL-1β), and apoptosis in ischemic brain injury. Because IL-1β converting enzyme (ICE) is required for the conversion of proIL-1β to its biologically active form, and has homology with proteins that regulate apoptosis in invertebrates, we studied the effect of cerebral ischemia on brain injury in mutant mice deficient in the ICE gene (ICE knockout [KO] mice). Focal cerebral ischemia, produced by occlusion of the middle cerebral artery, resulted in brain edema (increased water and sodium content) at 4 hours and a histologically defined brain lesion at 24 hours. Both of these markers of brain injury were significantly reduced in the ICE KO mice as compared to wild-type C57BL/6 mice. Regional cerebral blood flow, determined using the flow tracer, N-isopropyl [methyl 1,3-14C] p-iodoamphetamine (14C-IMP), was similar in the two strains of mice, indicating that the reduced brain injury in the KO mice was not a result of a lesser degree of ischemia. These data show that ICE contributes to the development of ischemic brain damage, and that it plays a role at an early time in the pathologic process. Although the mechanism of this effect is uncertain, our results suggest that pharmacologic inhibition of ICE may be a useful treatment for stroke.

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Attenuation of Ischemic Inflammatory Response in Mouse Brain Using an Adenoviral Vector to Induce Overexpression of Interleukin-1 Receptor Antagonist

Journal of Cerebral Blood Flow & Metabolism ◽

10.1097/00004647-199808000-00004 ◽

1998 ◽

Vol 18 (8) ◽

pp. 840-847 ◽

Cited By ~ 56

Author(s):

Guo-Yuan Yang ◽

Xiao-Hong Liu ◽

Chitoshi Kadoya ◽

Yong-Jie Zhao ◽

Ying Mao ◽

...

Keyword(s):

Brain Injury ◽

Basal Ganglia ◽

Inflammatory Response ◽

Receptor Antagonist ◽

Adenoviral Vector ◽

Interleukin 1 ◽

Saline Control ◽

Ischemic Brain Injury ◽

Ischemic Brain ◽

Interleukin 1 Receptor Antagonist

It has been demonstrated that administration of an interleukin-1 receptor antagonist protein (IL-1ra) reduces ischemic brain injury; however, the detrimental mechanism initiated by interleukin-1 (IL-1) in ischemic brain injury is unclear. In this study, we used mice that were transfected to overexpress human IL-1ra to elucidate the role of IL-1 in the activation of the inflammatory response after middle cerebral artery occlusion (MCAO). Myeloperoxidase (MPO) activity and immunohistostaining were used as a marker of polymorphonuclear leukocytes (PMNL) infiltration. Adenoviral vector (1 × 109 particles) was administered by injection into the right lateral ventricle in mice. Five days later, MCAO was performed on the mice using a suture technique. Permanent MCAO was achieved for 24 hours in the Ad.RSV IL-1ra-transfected, Ad.RSV lacZ-transfected, and saline (control) mice. Myeloperoxidase activity was quantified in each region and localization of MPO was determined by immunohistochemistry. After 2 hours of MCAO, the surface cerebral blood flow was reduced to 13.5% ± 3.4%, 10.75% ± 2.6%, and 10.9% ± 2.6% of baseline in the ischemic hemisphere in Ad.RSV IL-1ra-transfected, Ad.RSV- lacZ-transfected, and saline-treated mice, respectively. The MPO activity in the ischemic hemisphere in the Ad.RSV lacZ group was similar to that in the saline control group (cortex: 0.40 ± 0.22 versus 0.33 ± 0.11; basal ganglia: 0.46 ± 0.23 versus 0.49 ± 0.17; P > 0.05); however, it was significantly reduced in the Ad.RSV IL-1ra group (cortex: 0.18 ± 0.07; basal ganglia: 0.26 ± 0.15; P < 0.05). Myeloperoxidase immunohistochemistry showed that the massive accumulation of MPO-positive cells in the ischemic cortex, striatum, and corpus callosum regions was greatly attenuated in Ad.RSV IL-1ra-transfected mice. Our results indicate that Ad.RSV IL-1ra-transfected mice provide a useful tool to study the mechanism of action of IL-1. The MPO activity assay and immunostaining after 24 hours of focal ischemia were significantly reduced in IL-1ra gene-transfected mice, suggesting that IL-1 may play an important role in the activation of inflammatory cells during focal cerebral ischemia.

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Abstract 005: A Small-molecule Inhibitor of NLRP3 Inflammasome Activity, MCC950, Reduces Blood Pressure and Restores Renal Function in Hypertensive Mice

Hypertension ◽

10.1161/hyp.68.suppl_1.005 ◽

2016 ◽

Vol 68 (suppl_1) ◽

Author(s):

Dorota M Ferens ◽

Shalini M Krishnan ◽

Michelle M Kett ◽

Yeong H Ling ◽

Katrina M Mirabito ◽

...

Keyword(s):

Blood Pressure ◽

Renal Function ◽

Small Molecule ◽

Nlrp3 Inflammasome ◽

Interleukin 1 ◽

Small Molecule Inhibitor ◽

Inflammasome Activation ◽

Molecule Inhibitor ◽

Elevated Expression ◽

Inflammasome Activity

Inflammasomes are a family of interleukin-1 processing complexes and master regulators of inflammation. We recently showed that both one-kidney/deoxycorticosterone acetate/salt (1K/DOCA/salt)- and angiotensin II-dependent hypertension in mice are associated with elevated expression of the NLRP3 inflammasome in the kidneys. Moreover, genetic deficiency of a key subunit critical for NLRP3 inflammasome activity protected mice against renal inflammation and chronic pressor responses associated with these models. As a step towards translation of these findings into new therapies, here we investigated whether a highly specific small-molecule inhibitor of NLRP3 inflammasome activity, MCC950, similarly reduces the deleterious effects of 1K/DOCA/salt on blood pressure (BP) and renal function. Male C57BL6/J mice were implanted with telemetry probes for continuous recording of BP (mean arterial (MAP), systolic, diastolic) and heart rate (HR), or placed in metabolic cages for 24 h urine collections to assess renal function. Once baseline parameters were established, mice were uninephrectomized, received a DOCA pellet (2.4 mg/kg/d, s.c. ) and were given 0.9% saline to drink. Following establishment of hypertension (10 d), mice were implanted with osmotic pumps containing either MCC950 (10 mg/kg/d, s.c. ) or vehicle (saline) and followed for 28 d. MAP increased from 102 ± 2 to 133 ± 3 mmHg over the 10 d following 1K/DOCA/salt surgery. In vehicle-treated mice, MAP remained at this elevated level until the end of the treatment period. By contrast, MAP of mice treated with MCC950 gradually declined such that at day 38 it was 15 mmHg lower than that of vehicle-treated mice. Systolic and diastolic BP response was similar to MAP, whereas HR was unaffected by MCC950. Urine, Na + and albumin excretion, and osmolality were all markedly increased after 10 d of 1K/DOCA/salt treatment. Consistent with its effect on BP, MCC950 decreased each of these parameters by 30-40%, whereas vehicle had no effects. In conclusion, we have shown that an inhibitor of NLRP3 inflammasome activation reduces BP and restores renal function in mice with established hypertension, highlighting MCC950 as a promising candidate for future therapies.

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