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Enhanced Ca2+ handling in thioglycolate-elicited peritoneal macrophages
Feng Liu1, Luxin Xu1, Miyuki Nishi1
1Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto, 606-8501, Japan.
Abstract:
In macrophage biology, resident peritoneal macrophages (RPMs) and thioglycolate-elicited peritoneal macrophages (TGPMs) have been traditionally utilized as primary cultured models. RPMs and TGPMs exhibit distinct morphological, functional and metabolic characteristics, although it remains unclear how cellular Ca2+ handling differs between them. In our Fura-2 Ca2+ imaging, TGPMs displayed elevated resting Ca2+ levels, increased store Ca2+ contents and facilitated store-operated Ca2+ entry (SOCE) compared with RPMs. The intensified intracellular Ca2+ stores were enriched with major luminal Ca2+-binding proteins inducibly expressed in TGPMs. The elevated resting Ca2+ level was predominantly maintained by constitutive Ca2+ influx, probably through the transient receptor potential (TRP) family members TRPP2, TRPM7 and TRPA1. These TRP family channels seemed to be largely activated in a manner dependent on phospholipase C activity, and together with Orai channels, contributed to SOCE. Moreover, Ca2+-dependent K+ channels efficiently facilitated SOCE by enhancing the Ca2+ driving force in TGPMs. The consolidated cellular Ca2+ handling described may underlie the specialized cell-physiological features of TGPMs, such as vital proliferation, active migration and avid phagocytosis.
Insights
Thioglycolate-elicited peritoneal macrophages (TGPMs) show enhanced cellular calcium (Ca2+) handling compared to resident peritoneal macrophages (RPMs). This involves higher resting Ca2+ levels, increased Ca2+ stores, and facilitated store-operated Ca2+ entry (SOCE) in TGPMs.
Area of Science:
- Cellular Biology
- Immunology
- Macrophage Biology
Background:
- Resident peritoneal macrophages (RPMs) and thioglycolate-elicited peritoneal macrophages (TGPMs) are key models in macrophage research.
- Distinct functional and metabolic differences exist between RPMs and TGPMs, but their cellular calcium (Ca2+) handling disparities are not well understood.
Purpose of the Study:
- To investigate and compare the cellular Ca2+ handling mechanisms between RPMs and TGPMs.
- To elucidate the role of Ca2+ signaling in the specialized physiological features of TGPMs.
Main Methods:
- Utilized Fura-2 Ca2+ imaging to assess Ca2+ levels and dynamics in RPMs and TGPMs.
- Analyzed intracellular Ca2+ stores, store-operated Ca2+ entry (SOCE), and the involvement of transient receptor potential (TRP) channels and Ca2+-dependent K+ channels.
Main Results:
- TGPMs exhibited higher resting Ca2+ levels, greater intracellular Ca2+ store content, and enhanced SOCE compared to RPMs.
- Elevated resting Ca2+ in TGPMs is maintained by constitutive Ca2+ influx via TRPP2, TRPM7, and TRPA1 channels, activated by phospholipase C.
- Ca2+-dependent K+ channels facilitated SOCE in TGPMs by increasing the Ca2+ driving force.
Conclusions:
- TGPMs possess distinct and enhanced cellular Ca2+ handling mechanisms compared to RPMs.
- These Ca2+ handling differences, involving TRP and Orai channels, likely contribute to the specialized functions of TGPMs, including proliferation, migration, and phagocytosis.
