Investigating the Role of TNF-α and IFN-γ Activation on the Dynamics of iNOS Gene Expression in LPS Stimulated Macrophages

Abstract

Macrophage produced inducible nitric oxide synthase (iNOS) is known to play a critical role in the proinflammatory response against intracellular pathogens by promoting the generation of bactericidal reactive nitrogen species. Robust and timely production of nitric oxide (NO) by iNOS and analogous production of reactive oxygen species are critical components of an effective immune response. In addition to pathogen associated lipopolysaccharides (LPS), iNOS gene expression is dependent on numerous proinflammatory cytokines in the cellular microenvironment of the macrophage, two of which include interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α). To understand the synergistic effect of IFN-γ and TNF-α activation, and LPS stimulation on iNOS expression dynamics and NO production, we developed a systems biology based mathematical model. Using our model, we investigated the impact of pre-infection cytokine exposure, or priming, on the system. We explored the essentiality of IFN-γ priming to the robustness of initial proinflammatory response with respect to the ability of macrophages to produce reactive species needed for pathogen clearance. Results from our theoretical studies indicated that IFN-γ and subsequent activation of IRF1 are essential in consequential production of iNOS upon LPS stimulation. We showed that IFN-γ priming at low concentrations greatly increases the effector response of macrophages against intracellular pathogens. Ultimately the model demonstrated that although TNF-α contributed towards a more rapid response time, measured as time to reach maximum iNOS production, IFN-γ stimulation was significantly more significant in terms of the maximum expression of iNOS and the concentration of NO produced.

Assessment of the Number and Phenotype of Macrophages in the Human BMB Samples of CML

“…Macrophages are the hot spots of cancer research [7–11]. TAMs are highly plastic dictated by their microenvironment conceptualized into two opposing but complementary activation states: either proinflammatory M1-like TAMs or anti-inflammatory M2-like TAMs [29]. M2-like TAM are alternatively activated and produce anti-inflammatory cytokines like IL-4, IL-10, IL-13, transforming growth factor-b (TGF-b), and various chemokines to turn off damaging immune system activation and get involved in proliferation and survival of leukemia stem cell (LSCs), progression and metastasis, facilitating angiogenesis and lymphangiogenesis, matrix remodeling, and tumor cell-motility [30, 31].…”

<p>Functional aspects, phenotypic heterogeneity, and tissue immune response of macrophages in infectious diseases</p>

“…The first is the binding of IFN-γ or TNF-α to their respective receptors (IFN-γR or TNF-αR), whose main event is the development of intracellular cascade based on the activation of JAK1 and JAK2 and STAT1 or STAT2 responsible for inducing the production of MHCII, IL-12, and iNOS. [126][127][128] We cannot fail to mention the importance of GM-CSF in mediating NOS2 production. MHC class II, IL-12b, which is dependent on the activation of JAK2 and STAT5 and phosphorylation of IRF5.…”

“…[169][170][171] As a final outcome, NF-kB is responsible for inducing the production of pro-inflammatory cytokines such as TNF-α, IFN-γ, IL-1β, and IL-6 that participate in the activation of macrophages and enzymes such as iNOS, which is responsible the generation of ROS and destruction of the microorganism. 126,172,173 However, the immune evasion strategies adopted by mycobacteria include a series of events aimed at inactivating this mechanism. With regard to M. tuberculosis, TLR2 is the main receptor by which mycobacteria modulate immune escape.…”

Experimental control of macrophage pro-inflammatory dynamics using predictive models

“…However, macrophage functional diversity and broad distribution throughout the body also makes them excellent targets for modulating immune function to treat an array of diseases 23 . Yet the vast majority of new immunomodulatory strategies, including inflammatory inhibitors and cell-based therapies, do not explicitly account for the temporal evolution of macrophage response needed to resolve the response to injury.…”

“…1a,b). The pathways governing macrophage polarization in response to stimuli have been comprehensively modeled, including receptor binding kinetics, downstream kinase signaling, and gene transcription 23 . While mechanistically appealing, these models possess dozens of equations and hundreds of parameters, making it intractable to identify reliably predictive input-output relationships between exogenous stimulation and polarization in terms of these precise mechanistic models.…”