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Free Radic Biol Med. 2016 Dec;101:102-115. doi: 10.1016/j.freeradbiomed.2016.10.001. Epub 2016 Oct 4.

MKK3 influences mitophagy and is involved in cigarette smoke-induced inflammation.

Author information

1
Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520-8057, USA. Electronic address: praveen.mannam@yale.edu.
2
MS & Proteomics Resource at Yale University, WM Keck Foundation Biotechnology Resource Laboratory, Department of Molecular Biophysics and Biochemistry, New Haven, CT 06520-8057, USA.
3
Department of Epidemiology & Biostatistics, School of Public Health, Georgia State University, Atlanta, GA, USA.
4
Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520-8057, USA.
5
Pulmonary, Critical Care and Sleep Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520-8057, USA. Electronic address: anup.srivastava@yale.edu.

Abstract

Cigarette smoking is the primary risk factor for COPD which is characterized by excessive inflammation and airflow obstruction of the lung. While inflammation is causally related to initiation and progression of COPD, the mitochondrial mechanisms that underlie the associated inflammatory responses are poorly understood. In this context, we have studied the role played by Mitogen activated protein (MAP) kinase kinase 3 (MKK3), a dual-specificity protein kinase, in cigarette smoke induced-inflammation and mitochondrial dysfunction. Serum pro-inflammatory cytokines were significantly elevated in WT but not in MKK3-/- mice exposed to Cigarette smoke (CS) for 2 months. To study the cellular mechanisms of inflammation, bone marrow derived macrophages (BMDMs), wild type (WT) and MKK3-/-, were exposed to cigarette smoke extract (CSE) and inflammatory cytokine production and mitochondrial function assessed. The levels of IL-1β, IL-6, and TNFα were increased along with higher reactive oxygen species (ROS) and P-NFκB after CSE treatment in WT but not in MKK3-/- BMDMs. CSE treatment adversely affected basal mitochondrial respiration, ATP production, maximum respiratory capacity, and spare respiratory capacity in WT BMDMs only. Mitophagy, clearance of dysfunctional mitochondria, was up regulated in CS exposed WT mice lung tissue and CSE exposed WT BMDMs, respectively. The proteomic analysis of BMDMs by iTRAQ (isobaric tags for relative and absolute quantitation) showed up regulation of mitochondrial dysfunction associated proteins in WT and higher OXPHOS (Oxidative phosphorylation) and IL-10 signaling proteins in MKK3-/- BMDMs after CSE exposure, confirming the critical role of mitochondrial homeostasis. Interestingly, we found increased levels of p-MKK3 by immunohistochemistry in COPD patient lung tissues that could be responsible for insufficient mitophagy and disease progression. This study identifies MKK3 as a negative regulator of mitochondrial function and inflammatory responses to CS and suggests that MKK3 could be a therapeutic target.

KEYWORDS:

Cigarette Smoke; Inflammation; MAP kinase Kinase 3; Mitochondria; Mitophagy

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