The role of Rho-kinases in IL-1β release through phagocytosis of fibrous particles in human monocytes

Our plain-English summary of The role of Rho-kinases in IL-1β release through phagocytosis of fibrous particles in human monocytes, by S. Kanno, S. Hirano, S. Chiba, et al (Archives of Toxicology, 2015).

The study

• Authors: S. Kanno, S. Hirano, S. Chiba, H. Takeshita, T. Nagai, M. Takada, K. Sakamoto, T. Mukai
• Journal: Archives of Toxicology
• Published: 2015;89(1):73-85
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Long fibers, such as asbestos and carbon nanotubes (CNTs), are more potent activators of inflammatory and genotoxicity than short or tangled fibers. Fibrous particles trigger interleukin (IL)-1β secretion and cause inflammatory diseases through NLRP3 inflammasomes in phagocytotic cells. However, the mechanism involved in fibrous particle-induced inflammation has not been well documented. In this study, we focused on GTPase effector Rho-kinases (ROCK1, and 2), which are known to be involved in a wide range of cellular functions such as adhesion, regulation of cytoskeleton, and phagocytosis. We examined whether ROCKs are associated with multi-walled CNT (MWCNT)- or asbestos-induced IL-1β secretion in human monocytic THP-1 cells using a selective inhibitor and small interfering RNA. THP-1 cells were differentiated to macrophages by PMA and were exposed to MWCNTs, crocidolite asbestos or lipopolysaccharide (LPS) in the presence or absence of Y27632 (ROCK inhibitor) or Z-YVAD (caspase-1 inhibitor). Exposure of the cells to MWCNTs or asbestos provoked IL-1β secretion, but this secretion was suppressed by both Y27632 and Z-YVAD, whereas LPS-induced IL-1β secretion was inhibited only by Z-YVAD and not by Y27632. siRNA designed for knockdown of both ROCK1 and ROCK2 suppressed MWCNT- and asbestos-induced IL-1β secretion, but did not change LPS-induced IL-1β secretion. Moreover, Y27632 suppressed pro-IL-1β protein levels and the release of activated-cathepsin B and activated-caspase-1 induced by MWCNTs or asbestos. In contrast, LPS-induced pro-IL-1β protein was not suppressed by Y27632. These results suggest that ROCKs are involved in fibrous particle-induced inflammasome responses in THP-1 cells.

In plain English

This was a laboratory cell-culture experiment testing whether Rho-kinases (ROCK1 and ROCK2) are involved in interleukin-1β (IL-1β) release triggered by fibrous particles. Human monocytic THP-1 cells were differentiated into macrophages with PMA and exposed for 12 hours to multi-walled carbon nanotubes (2-10 micrograms per ml), UICC crocidolite asbestos (20-100 micrograms per ml), monosodium urate crystals or lipopolysaccharide (LPS), with or without the ROCK inhibitor Y27632, the caspase-1 inhibitor Z-YVAD, or cytochalasin D. PMA differentiation increased ROCK1 but not ROCK2. MWCNTs and asbestos raised IL-1β secretion dose-dependently; Z-YVAD suppressed IL-1β from all three stimuli, while Y27632 and siRNA knockdown of ROCK1 and ROCK2 reduced MWCNT- and asbestos-induced but not LPS-induced IL-1β. Y27632 cut the rise in pro-IL-1β produced by MWCNTs or asbestos to about 65 percent of that effect, measured by densitometry as the pro-IL-1β to tubulin ratio, and lowered release of activated caspase-1 and activated cathepsin B after fibre exposure, but did not change the amount of cell-associated particles. The authors concluded that ROCKs are involved in fibrous particle-induced inflammasome responses in THP-1 cells.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: In vitro cell-culture (molecular toxicology) experiment using a human monocytic cell line with chemical inhibitors and siRNA knockdown
• Who was studied: THP-1 human monocytic cell line (from ATCC), differentiated into macrophages with 100 nM PMA for 24 h; experiments replicated three or four times
• Exposure: Multi-walled carbon nanotubes (XNRI WMVT-7; average diameter 67 nm) 2-10 micrograms per ml, UICC crocidolite asbestos (average fibre length 2.5 micrometres, width 0.33 micrometres) 20-100 micrograms per ml, monosodium urate crystals 1 mg/ml, and LPS 0.1 micrograms per ml, with or without 10 micromolar Y27632, 10 micromolar Z-YVAD or 1 microgram per ml cytochalasin D
• Main results:
  • PMA differentiation increased ROCK1 protein in THP-1 cells, while ROCK2 was unchanged
  • The caspase-1 inhibitor Z-YVAD significantly suppressed IL-1β secretion induced by MWCNTs, asbestos and LPS in both primed and unprimed cells
  • The ROCK inhibitor Y27632 produced a slight but statistically significant reduction in IL-1β induced by the fibrous particles, with less effect on LPS-induced IL-1β
  • siRNA knockdown of ROCK1 or ROCK2 significantly decreased MWCNT- and asbestos-induced IL-1β but not LPS-induced IL-1β
  • Y27632 decreased the MWCNT- and asbestos-induced increase in pro-IL-1β to about 65 percent, judged by densitometry of the pro-IL-1β to tubulin ratio, but did not affect the LPS-induced increase in pro-IL-1β
  • Activated caspase-1 (p20) was released into the supernatant after MWCNT and asbestos exposure but not after LPS
  • Activated cathepsin B (27 kDa) was released after MWCNT and asbestos exposure but not after LPS, and Y27632 reduced this release
  • Cytochalasin D suppressed MWCNT- and asbestos-induced IL-1β but not LPS-induced IL-1β
  • Y27632 did not change the amount of cell-associated MWCNTs or asbestos; separately, viability assays showed Y27632 diminished MWCNT- and asbestos-induced cytotoxicity
• The authors' conclusion: The authors concluded that the ROCK inhibitor and siRNA against both ROCK1 and ROCK2 decreased asbestos- and MWCNT-induced IL-1β secretion in differentiated THP-1 cells without affecting LPS-induced secretion, suggesting ROCKs are involved in fibrous particle-induced inflammasome responses
• Limitations the authors state:
  • The particle uptake measurement could not separate phagocytosed particles from particles bound to the cell membrane
  • The authors stated that further study is needed to elucidate how ROCKs act on NLRP3 inflammasomes activated by fibrous particles
  • Some observations (microscopic findings on cell morphology) were reported only as data not shown
  • The fibre length of the MWCNTs used was not specified

Topics

Medical terms in this study, explained in our Lexicon: Phagocytosis, Genotoxicity, Inflammation, Macrophage, Crocidolite.

Related studies

• Double-walled carbon nanotubes trigger IL-1β release in human monocytes through Nlrp3 inflammasome activation — E. Meunier, A. Coste, et al. (2012)
• Nanoparticles activate the NLR pyrin domain containing 3 (Nlrp3) inflammasome and cause pulmonary inflammation through release of IL-1α and IL-1β — A.S. Yazdi, G. Guarda, et al. (2010)
• Long, needle-like carbon nanotubes and asbestos activate the NLRP3 inflammasome through a similar mechanism — J. Palomäki, E. Välimäki, et al. (2011)
• The NLRP3 inflammasome is activated by nanoparticles through ATP, ADP and adenosine — L. Baron, A. Gombault, et al. (2015)
• Orthopedic wear debris mediated inflammatory osteolysis is mediated in part by NALP3 inflammasome activation — L. Burton, D. Paget, et al. (2013)
• High-temperature calcined fullerene nanowhiskers as well as long needle-like multi-wall carbon nanotubes have abilities to induce NLRP3-mediated IL-1β secretion — H. Cui, W. Wu, et al. (2014)

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