Dataset Information

Caspase-1 Activation Protects Lung Endothelial Barrier Function during Infection-Induced Stress.

ABSTRACT: Dysregulated activation of the inflammasome-caspase-1-IL-1? axis elicits damaging hyperinflammation during critical illnesses, such as pneumonia and sepsis. However, in critical illness models of Salmonella infection, burn, or shock, caspase-1 inhibition worsens outcomes. These paradoxical effects suggest that caspase-1 drives novel protective responses. Whether the protective effects of caspase-1 activation involve canonical immune cell and/or nonimmune cell responses is unknown. The objective of this study was to test the hypothesis that, in addition to its recognized proinflammatory function, caspase-1 initiates protective stress responses in nonimmune cells. In vivo, lung epithelial and endothelial barrier function and inflammation were assessed in mice infected with Pseudomonas aeruginosa in the presence or absence of a caspase-1 inhibitor. Lung endothelial barrier function was assessed ex vivo in isolated, perfused rat lungs infected with P. aeruginosa in the presence or absence of a caspase-1 inhibitor. Endothelial barrier function during P. aeruginosa infection was assessed in vitro in cultured rat wild-type pulmonary microvascular endothelial cells (PMVECs) or recombinant PMVECs engineered to decrease caspase-1 expression. We demonstrated in vivo that caspase-1 inhibition in P. aeruginosa-infected mice ameliorated hyperinflammation, but, counterintuitively, increased pulmonary edema. Ex vivo, caspase-1 inhibition increased pulmonary permeability in P. aeruginosa-infected isolated rat lungs. To uncouple caspase-1 from its canonical inflammatory role, we used cultured rat PMVECs in vitro and discovered that genetic knockdown of caspase-1 accelerated P. aeruginosa-induced barrier disruption. In conclusion, caspase-1 is a sentinel stress-response regulator that initiates proinflammatory responses and also initiates novel response(s) to protect PMVEC barrier function during pneumonia.

SUBMITTER: Alvarez DF

PROVIDER: S-EPMC5070108 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Caspase-1 Activation Protects Lung Endothelial Barrier Function during Infection-Induced Stress.

Alvarez Diego F DF Housley Nicole N Koloteva Anna A Zhou Chun C O'Donnell Kristen K Audia Jonathon P JP

American journal of respiratory cell and molecular biology 20161001 4

Dysregulated activation of the inflammasome-caspase-1-IL-1β axis elicits damaging hyperinflammation during critical illnesses, such as pneumonia and sepsis. However, in critical illness models of Salmonella infection, burn, or shock, caspase-1 inhibition worsens outcomes. These paradoxical effects suggest that caspase-1 drives novel protective responses. Whether the protective effects of caspase-1 activation involve canonical immune cell and/or nonimmune cell responses is unknown. The objective ...[more]

PMID: 27119735

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Project description:Heatstroke (HS) can cause acute lung injury (ALI). Heat stress induces inflammation and apoptosis via reactive oxygen species (ROS) and endogenous reactive aldehydes. Endothelial dysfunction also plays a crucial role in HS-induced ALI. Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme that detoxifies aldehydes such as 4-hydroxy-2-nonenal (4-HNE) protein adducts. A single point mutation in ALDH2 at E487K (ALDH2*2) intrinsically lowers the activity of ALDH2. Alda-1, an ALDH2 activator, attenuates the formation of 4-HNE protein adducts and ROS in several disease models. We hypothesized that ALDH2 can protect against heat stress-induced vascular inflammation and the accumulation of ROS and toxic aldehydes. Homozygous ALDH2*2 knock-in (KI) mice on a C57BL/6J background and C57BL/6J mice were used for the animal experiments. Human umbilical vein endothelial cells (HUVECs) were used for the in vitro experiment. The mice were directly subjected to whole-body heating (WBH, 42°C) for 1 h at 80% relative humidity. Alda-1 (16 mg/kg) was administered intraperitoneally prior to WBH. The severity of ALI was assessed by analyzing the protein levels and cell counts in the bronchoalveolar lavage fluid, the wet/dry ratio and histology. ALDH2*2 KI mice were susceptible to HS-induced ALI in vivo. Silencing ALDH2 induced 4-HNE and ROS accumulation in HUVECs subjected to heat stress. Alda-1 attenuated the heat stress-induced activation of inflammatory pathways, senescence and apoptosis in HUVECs. The lung homogenates of mice pretreated with Alda-1 exhibited significantly elevated ALDH2 activity and decreased ROS accumulation after WBH. Alda-1 significantly decreased the WBH-induced accumulation of 4-HNE and p65 and p38 activation. Here, we demonstrated the crucial roles of ALDH2 in protecting against heat stress-induced ROS production and vascular inflammation and preserving the viability of ECs. The activation of ALDH2 by Alda-1 attenuates WBH-induced ALI in vivo.

Project description:Recent research has revealed that uncontrolled chronic neuroinflammation is closely associated with diverse neurodegenerative diseases, by impairing blood-brain barrier (BBB) function and astrocytic reaction. Endoplasmic reticulum (ER) stress is conventionally linked to the loss of neuronal structure and function and should be widely attenuated. This notion has been questioned by recent experimental studies, which have shown that non-harmful levels of ER stress had numerous beneficial roles against neurodegeneration, including neuroprotection and inhibition of cytokine production. Here, we investigated the mild ER stress-based regulation of LPS-induced inflammatory responses in astrocytes. Primary astrocytes were exposed to tunicamycin (TM), a compound that activates ER stress, with or without the ER-stress inhibitor sodium 4-phenylbutyrate (4-PBA) before LPS treatment. Astrocytic activation, proinflammatory factor production, and the extent of ER stress were assessed. In addition, the effect of mild ER stress on astrocytes and BBB function was determined in vivo. Male Sprague-Dawley rats received intracerebroventricular injections of TM with or without intraperitoneal 4-PBA before LPS administration. The levels of astrocytic activation and BBB permeability were measured after treatment. Our results showed that lower doses of TM resulted in a mild ER-stress response without inducing cytotoxicity and tissue toxicity. Non-toxic ER-stress preconditioning ameliorated LPS-induced overactivation and inflammatory responses in astrocytes. Moreover, pre-exposure to non-lethal doses of TM improved LPS-induced BBB impairment and cognitive ability dysfunction in rats. However, 4-PBA, reversed the protective effect of TM preconditioning in vitro and in vivo. We conclude that mild ER stress ("preconditioning") can alleviate LPS-induced astrocytic activation and BBB disruption. Our findings provide a better understanding for the regulatory role of ER stress in neuroinflammation and indicate that mild ER stress might have therapeutic value for the treatment of neurodegenerative diseases.

Dataset Information

Caspase-1 Activation Protects Lung Endothelial Barrier Function during Infection-Induced Stress.

Publications

Caspase-1 Activation Protects Lung Endothelial Barrier Function during Infection-Induced Stress.

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