Related Experiment Videos
When do human macrophages release nitric oxide? Variable effects of certain in vitro cultural and in vivo resident
1Department of Pediatrics, Tri-Service General Hospital, Taipei, Taiwan, R.O.C.
Abstract:
Nitric oxide (NO) release from mouse and rat macrophages is implicated in tumor cell cytotoxicity and the killing of intracellular organisms. Evidence, however, suggests that human monocyte-derived macrophages or myeloid leukemic cells differentiated along the monocytic lineage do not consistently release NO. Results presented herein that human monocyte-derived macrophages in response to lipopolysaccharide can release NO, but markedly less than mouse macrophages (1.26 +/- 0.20 vs 42.5 +/- 6.3 microM). Different in vitro and in vivo conditions have variable effects on NO production by human macrophages. Monocytes cultured in plastic wells, but not teflon beakers, for 7 days can release NO (1.22 +/- 0.13 vs 0.14 +/- 0.07 microM). In addition, human resident macrophages derived from patients with certain diseases possess a calcium- and protein kinase C-dependent pathway to produce NO, in contrast to the calcium-independent and phosphatase-dependent NO release in murine macrophages. Above results suggest that the mechanism of producing NO by macrophages in humans is not only different from that in mice, but also depends on certain in vitro and in vivo conditions.
Insights
Human macrophages release significantly less nitric oxide (NO) than mouse macrophages. NO production in humans is influenced by culture conditions and disease, unlike in mice.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Nitric oxide (NO) release from macrophages is crucial for tumor cell cytotoxicity and fighting intracellular pathogens in mice.
- However, human monocyte-derived macrophages and certain human myeloid cells reportedly exhibit inconsistent NO production.
- This discrepancy highlights a potential difference in NO-mediated immune responses between species.
Purpose of the Study:
- To investigate the capacity of human monocyte-derived macrophages to release nitric oxide (NO).
- To compare NO production levels between human and murine macrophages.
- To explore the influence of in vitro and in vivo conditions on human macrophage NO synthesis and signaling pathways.
Main Methods:
- Human monocytes were differentiated into macrophages in vitro under various conditions (plastic wells vs. Teflon beakers) for 7 days.
- Lipopolysaccharide (LPS) stimulation was used to induce NO release.
- Nitric oxide levels were quantified using microMolar measurements.
- Signaling pathways (calcium-dependent, protein kinase C, phosphatase-dependent) were investigated in human and murine macrophages.
Main Results:
- Human monocyte-derived macrophages produced NO in response to LPS, but at significantly lower levels (1.26 +/- 0.20 microM) compared to mouse macrophages (42.5 +/- 6.3 microM).
- Macrophage culture in plastic wells for 7 days supported NO release (1.22 +/- 0.13 microM), whereas Teflon beakers did not (0.14 +/- 0.07 microM).
- Human macrophages utilized a calcium- and protein kinase C-dependent pathway for NO production, distinct from the calcium-independent, phosphatase-dependent pathway in murine macrophages.
Conclusions:
- Human monocyte-derived macrophages can produce nitric oxide (NO), albeit at much lower levels than murine macrophages.
- NO production in human macrophages is highly sensitive to in vitro culture conditions and potentially in vivo disease states.
- The signaling mechanisms regulating NO synthesis in human macrophages differ fundamentally from those in murine macrophages, indicating species-specific regulation.