Macrophages and Tissue Injury: Agents of Defense or Destruction?

Department of Pharmacology and Toxicology, Rutgers University, Piscataway, New Jersey 08854, USA.
Annual Review of Pharmacology (Impact Factor: 18.37). 11/2010; 51(1):267-88. DOI: 10.1146/annurev.pharmtox.010909.105812
Source: PubMed


The past several years have seen the accumulation of evidence demonstrating that tissue injury induced by diverse toxicants is due not only to their direct effects on target tissues but also indirectly to the actions of resident and infiltrating macrophages. These cells release an array of mediators with cytotoxic, pro- and anti-inflammatory, angiogenic, fibrogenic, and mitogenic activity, which function to fight infections, limit tissue injury, and promote wound healing. However, following exposure to toxicants, macrophages can become hyperresponsive, resulting in uncontrolled or dysregulated release of mediators that exacerbate acute tissue injury and/or promote the development of chronic diseases such as fibrosis and cancer. Evidence suggests that the diverse activity of macrophages is mediated by distinct subpopulations that develop in response to signals within their microenvironment. Understanding the precise roles of these different macrophage populations in the pathogenic response to toxicants is key to designing effective treatments for minimizing tissue damage and chronic disease and for facilitating wound repair.

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    • "However, NK cells seem to play a role in pancreas resistance to CVB infection [43] but do not alter the cardiac viral clearance after its depletion [44], or inhibition [45]. Taken together , it seems that in CVB3-induced myocarditis, cardiac infiltrating macrophages have a major role in the early clearance of infected cardiomyocytes in accordance with the assigned dual role of macrophages not only limiting tissue injury but also increasing tissue damage [46]. The fact that macrophage-depleted mice also presented lower body weight suggests that besides their role in chronic myocarditis, macrophages might have additional roles, controlling viral replication and/or tissue damage in other organs. "
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    • "The infiltration of inflammatory macrophages is associated with the progression of lung injury and pathology [60,61]. However macrophage diversity is revealing the importance of lung macrophages in both the injury and repair stages [16], and differential activation suggests that a GM-CSF driven M1 pro-inflammatory response may be distinct from CSF-1-mediated stimulation of macrophages to take on a remodelling/anti-inflammatory M2 phenotype [29]. "
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    ABSTRACT: Background Lung immaturity due to preterm birth is a significant complication affecting neonatal health. Despite the detrimental effects of supplemental oxygen on alveolar formation, it remains an important treatment for infants with respiratory distress. Macrophages are traditionally associated with the propagation of inflammatory insults, however increased appreciation of their diversity has revealed essential functions in development and regeneration.Methods Macrophage regulatory cytokine Colony-Stimulating Factor-1 (CSF-1) was investigated in a model of neonatal hyperoxia exposure, with the aim of promoting macrophages associated with alveologenesis to protect/rescue lung development and function. Neonatal mice were exposed to normoxia (21% oxygen) or hyperoxia (Hyp; 65% oxygen); and administered CSF-1 (0.5 ¿g/g, daily¿×¿5) or vehicle (PBS) in two treatment regimes; 1) after hyperoxia from postnatal day (P)7-11, or 2) concurrently with five days of hyperoxia from P1-5. Lung structure, function and macrophages were assessed using alveolar morphometry, barometric whole-body plethysmography and flow cytometry.Results and discussionSeven days of hyperoxia resulted in an 18% decrease in body weight and perturbation of lung structure and function. In regime 1, growth restriction persisted in the Hyp¿+¿PBS and Hyp¿+¿CSF-1 groups, although perturbations in respiratory function were resolved by P35. CSF-1 increased CSF-1R+/F4/80+ macrophage number by 34% at P11 compared to Hyp¿+¿PBS, but was not associated with growth or lung structural rescue. In regime 2, five days of hyperoxia did not cause initial growth restriction in the Hyp¿+¿PBS and Hyp¿+¿CSF-1 groups, although body weight was decreased at P35 with CSF-1. CSF-1 was not associated with increased macrophages, or with functional perturbation in the adult. Overall, CSF-1 did not rescue the growth and lung defects associated with hyperoxia in this model; however, an increase in CSF-1R+ macrophages was not associated with an exacerbation of lung injury. The trophic functions of macrophages in lung development requires further elucidation in order to explore macrophage modulation as a strategy for promoting lung maturation.
    Respiratory Research 09/2014; 15(1):110. DOI:10.1186/s12931-014-0110-5 · 3.09 Impact Factor
    • "It has been known that there are two classified groups of macrophages with the opposite role in inflammation, M1 and M2. Especially, M1 macrophages (pro-inflammatory) polarized by cytokines from Th1 cells might positively regulate hepatic fibrosis.[3132] TNF-α produced by macrophages activates NF-κB signaling via the activation of IκB-kinase complex. "
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    ABSTRACT: Background:During the process of hepatic fibrosis, the activation of hepatic stellate cells (HSCs) is responsible for the increased formation and reduced degradation of extracellular matrix in the liver. By employing the hepatic stellate cell line, HSC-T6, it was found that the methanol extract of Limonium tetragonum, a halophyte living in salt marsh near south and western seashores of Korea significantly inhibited the proliferation of HSC-T6 cells.Objective:In the present study, we attempted to investigate the antifibrotic effects of the mathanolic extract of L. tetragonum (MELT) in the activated HSC-T6 cells.Materials and Methods:The proliferation of HSC-T6 was stimulated by culturing environment or platelet-derived growth factor (PDGF-BB) insult, and then the inhibitory activities of MELT were measured.Results:It was found that MELT suppressed the proliferation of the activated HSC-T6 in concentration- and time-dependent manners. The increased collagen deposition in the activated HSC-T6 cells was also decreased by the treatment of MELT. The maximal dose of MELT, however, had little effect on primary cultured rat hepatocytes. Wlammatory cytokine, tumor necrosis factor alpha (TNF-α) produced by lipopolysaccharide-stimulated RAW264.7 macrophages was inhibited by MELT.Conclusion:Collectively, the above results demonstrated that MELT suppressed HSCs proliferation but not in hepatocytes, implying that L. tetragonum may be useful candidates for developing therapeutic agents for the prevention and treatment of hepatic fibrosis.
    Pharmacognosy Magazine 08/2014; 10(Suppl 3):S563-8. DOI:10.4103/0973-1296.139783 · 1.26 Impact Factor
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