Faculty Collaboration Database

Cardiotonic Steroids Stimulate Macrophage Inflammatory Responses Through a Pathway Involving CD36, TLR4, and Na/K-ATPase. Arterioscler Thromb Vasc Biol 2017 Aug;37(8):1462-1469

Date

06/18/2017

Pubmed ID

28619997

Pubmed Central ID

PMC5532064

DOI

10.1161/ATVBAHA.117.309444

Scopus ID

2-s2.0-85020518621 (requires institutional sign-in at Scopus site)   22 Citations

Abstract

OBJECTIVE: Circulating levels of cardiotonic steroids (CTS) are elevated in various chronic inflammatory conditions, but the role of CTS in inflammation remains largely unknown. We have previously shown that the CTS ouabain stimulates proinflammatory responses in murine macrophages. In this study, we aim to explore the mechanism how CTS induce proinflammatory responses in primary murine and human macrophages.

APPROACH AND RESULTS: Using both murine peritoneal macrophages and human monocyte-derived macrophages, we demonstrated that ouabain activated NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells), leading to proinflammatory cytokine (eg, MCP-1 [monocyte chemotactic protein 1], TNF-α [tumor necrosis factor-α], IL-1β [interleukin-1β], and IL-6) production. By applying siRNA techniques and murine peritoneal macrophages isolated from genetically modified mice, we showed that macrophages partially deficient in Na/K-ATPase, the receptor for CTS, or fully deficient in the scavenger receptor CD36 or TLR4 (Toll-like receptor) were resistant to ouabain-induced NF-κB activation, suggesting an indispensable role of these 3 receptors in this pathway. Mechanistically, this effect of ouabain was independent of the ion transport function of the Na/K-ATPase. Instead, ouabain stimulated a signaling complex, including Na/K-ATPase, CD36, and TLR4. Subsequently, TLR4 recruited MyD88 adaptor protein for NF-κB activation. Furthermore, intraperitoneal injection of ouabain into mice specifically recruited Ly6C⁺CCR2⁺ monocyte subtypes to the peritoneal cavities, indicating that the CTS ouabain triggers inflammation in vivo.

CONCLUSIONS: CTS activate NF-κB leading to proinflammatory cytokine production in primary macrophages through a signaling complex, including CD36, TLR4, and Na/K-ATPase. These findings warrant further studies on endogenous CTS in chronic inflammatory diseases, such as atherosclerosis.

Author List

Chen Y, Huang W, Yang M, Xin G, Cui W, Xie Z, Silverstein RL

Authors

Yiliang Chen PhD Assistant Professor in the Medicine department at Medical College of Wisconsin
Roy L. Silverstein MD Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
CD36 Antigens
Cardiotonic Agents
Cells, Cultured
Cytokines
Dose-Response Relationship, Drug
Enzyme Activation
Female
Inflammation
Inflammation Mediators
Macrophages, Peritoneal
Male
Mice
Mice, Inbred C57BL
Mice, Knockout
Myeloid Differentiation Factor 88
NF-kappa B
Ouabain
RNA Interference
Signal Transduction
Sodium-Potassium-Exchanging ATPase
Time Factors
Toll-Like Receptor 4
Transfection