Basic Study
Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Biol Chem. Jan 27, 2021; 12(1): 1-14
Published online Jan 27, 2021. doi: 10.4331/wjbc.v12.i1.1
Inhibition of matrix metalloproteinase-9 secretion by dimethyl sulfoxide and cyclic adenosine monophosphate in human monocytes
Darcy R Denner, Maria LD Udan-Johns, Michael R Nichols
Darcy R Denner, Maria LD Udan-Johns, Michael R Nichols, Department of Chemistry and Biochemistry, University of Missouri-St. Louis, St Louis, MO 63121, United States
Author contributions: Nichols MR conceived the ideas and supervised the project; Denner DR and Udan-Johns ML planned and carried out the experiments; Nichols MR wrote the manuscript in consultation with Denner DR and Udan-Johns ML. All authors have read and approve the final manuscript.
Supported by The University of Missouri-St. Louis, Alzheimer’s Association, No. NIRG-06-27267; and the Missouri Alzheimer’s and Related Disorders Research Program.
Institutional review board statement: The THP-1 human monocytic cell line was acquired commercially from American Type Culture Collection, thus no human subjects were used in this study.
Conflict-of-interest statement: There are no conflicts of interest to declare by any of the authors.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Michael R Nichols, PhD, Professor, Department of Chemistry and Biochemistry, University of Missouri-St. Louis, One University Blvd, St Louis, MO 63121, United States. nicholsmic@umsl.edu
Received: June 24, 2020
Peer-review started: June 24, 2020
First decision: November 4, 2020
Revised: November 17, 2020
Accepted: December 30, 2020
Article in press: December 30, 2020
Published online: January 27, 2021
Processing time: 204 Days and 18 Hours
ARTICLE HIGHLIGHTS
Research background

Matrix metalloproteinases (MMPs), including MMP-9, are an integral part of the immune response and are upregulated in response to a variety of stimuli. New details continue to emerge concerning the mechanistic and regulatory pathways that mediate MMP-9 secretion. There is significant evidence for regulation of inflammation by dimethyl sulfoxide (DMSO) and 3',5'-cyclic adenosine monophosphate (cAMP), thus investigation of how these two molecules may regulate both MMP-9 and tumor necrosis factor α (TNFα) secretion by human monocytes was of high interest. The hypothesis tested in this study was that DMSO and cAMP regulate MMP-9 and TNFα secretion by distinct mechanisms.

Research motivation

The objective of this study was further examine temporal and regulatory mechanisms of MMP-9 secretion in THP-1 human monocytes after stimulation with lipopolysaccharide (LPS). Specifically, dose-dependent regulation of MMP-9 and TNFα by the aprotic solvent DMSO and the intracellular signaling molecule cAMP.

Research objectives

The objective of this study was further examine temporal and regulatory mechanisms of MMP-9 secretion in THP-1 human monocytes after stimulation with LPS. Specifically, dose-dependent regulation of MMP-9 and TNFα by the aprotic solvent DMSO and the intracellular signaling molecule cAMP.

Research methods

The paper describes a basic research study using THP-1 human monocyte cells. All experiments were conducted at the University of Missouri-St. Louis in the Department of Chemistry and Biochemistry. Human monocyte cells were grown, cultured, and prepared for experiments in the University of Missouri-St. Louis Cell Culture Facility as per accepted guidelines. Cells were treated with LPS for selected exposure times and the conditioned medium was collected for analysis of MMP-9 and TNFα production. Inhibitors including DMSO, cAMP regulators, and anti-TNFα antibody were added to the cells prior to LPS treatment. MMP-9 secretion was analyzed by gel electrophoresis/western blot and quantitated by ImageJ software. TNFα secretion was analyzed by enzyme-linked immuno sorbent assay. All data is presented as the average and standard error for at least 3 trials. Statistical analysis was done using a two-tailed paired Student t-test P values less than 0.05 were considered significant and designated as such with an asterisk in the figures (P < 0.05). LPS and cAMP regulators were from Sigma-Aldrich, MMP-9 standard and antibody and TNFα antibodies were from R&D Systems, and amyloid-β peptide was from rPeptide.

Research results

In our investigation of MMP-9 secretion from THP-1 human monocytes, we made the following findings. Inclusion of DMSO in the cell treatment inhibited LPS-induced MMP-9, but not TNFα, secretion. Inclusion of DMSO in the cell treatment at different concentrations inhibited LPS-induced MMP-9 secretion in a dose-dependent fashion. A cell-permeable cAMP analog, dibutyryl cAMP, inhibited both LPS-induced MMP-9 and TNFα secretion. Pretreatment of the cells with the adenylyl cyclase activator forskolin inhibited LPS-induced MMP-9 and TNFα secretion. Pretreatment of the cells with the general cAMP phosphodiesterase inhibitor reduced LPS-induced MMP-9 and TNFα in a dose-dependent fashion. Pre-treatment of monocytes with an anti-TNFα antibody blocked LPS-induced MMP-9 and TNFα secretion. Amyloid-β peptide-induced MMP-9 secretion and occurred much later than TNFα secretion. The latter two findings strongly suggested an upstream role for TNFα in mediating LPS-stimulate MMP-9 secretion.

Research conclusions

The cumulative data indicated that MMP-9 secretion was a distinct process from TNFα secretion and occurred downstream. First, DMSO inhibited MMP-9, but not TNFα, suggesting that the MMP-9 secretion process was selectively altered. Second, cAMP inhibited both MMP-9 and TNFα with a similar potency, but at different monocyte cell exposure time points. The pattern of cAMP inhibition for these two molecules suggested that MMP-9 secretion lies downstream of TNFα and that TNFα may a key component of the pathway leading to MMP-9 secretion. This temporal relationship fit a model whereby early TNFα secretion directly led to later MMP-9 secretion. Lastly, antibody-blocking of TNFα diminished MMP-9 secretion, suggesting a direct link between TNFα secretion and MMP-9 secretion.

Research perspectives

Regulation of MMP-9 is a significant important in many disease processes including arthritis and Alzheimer’s disease. Further understanding of the pathways leading to MMP-9 secretion and regulation of this process will be important for managing human health.