A Defective TLR4 Signaling for IFN-β Expression Is Responsible for the Innately Lower Ability of BALB/c Macrophages to Produce NO in Response to LPS as Compared to C57BL/6

Abstract

C57BL/6 mice macrophages innately produce higher levels of NO than BALB/c cells when stimulated with LPS. Here, we investigated the molecular events that account for this intrinsic differential production of NO. We found that the lower production of NO in BALB/c is not due to a subtraction of L-arginine by arginase, and correlates with a lower iNOS accumulation, which is independent of its degradation rate. Instead, the lower accumulation of iNOS is due to the lower levels of iNOS mRNA, previously shown to be also independent of its stability, suggesting that iNOS transcription is less efficient in BALB/c than in C57BL/6 macrophages. Activation of NFκB is more efficient in BALB/c, thus not correlating with iNOS expression. Conversely, activation of STAT-1 does correlate with iNOS expression, being more prominent in C57BL/6 than in BALB/c macrophages. IFN-β and IL-10 are more highly expressed in C57BL/6 than in BALB/c macrophages, and the opposite is true for TNF-α. Whereas IL-10 and TNF-α do not seem to participate in their differential production of NO, IFN-β has a determinant role since 1) anti-IFN-β neutralizing antibodies abolish STAT-1 activation reducing NO production in C57BL/6 macrophages to levels as low as in BALB/c cells and 2) exogenous rIFN-β confers to LPS-stimulated BALB/c macrophages the ability to phosphorylate STAT-1 and to produce NO as efficiently as C57BL/6 cells. We demonstrate, for the first time, that BALB/c macrophages are innately lower NO producers than C57BL/6 cells because they are defective in the TLR-4-induced IFN-β-mediated STAT-1 activation pathway.

HDAC8 Inhibitor WK2-16 Therapeutically Targets Lipopolysaccharide-Induced Mouse Model of Neuroinflammation and Microglial Activation

“…We examined whether WK2-16 affected NF-κB, STATs, and MAPK signaling pathways, which regulate iNOS and COX-2 expression at the transcriptional level, to further clarify the underlying mechanisms. A previous study demonstrated that sufficient activation of STAT-1 was necessary for the full transcription of iNOS in macrophages, whereas NF-κB was activated [41]. STAT-1 and STAT-3 binding sites are widely located in the microglial genome, and manipulation of the constitutive expression of STAT-1 and STAT-3 mimics LPS stimulation, inducing the transcription of hundreds of genes and results in inflammatory cytokines production in microglia [42].…”

Multiorgan Development of Oxidative and Nitrosative Stress in LPS-Induced Endotoxemia in C57Bl/6 Mice: DHE-BasedIn VivoApproach

“…To evaluate this methodology, we used mice with lipopolysaccharide- (LPS-) induced endotoxemia, as this model is well characterized by an inflammatory reaction with an NADPH-oxidase-dependent oxidant burst and elevation in RNS through the inducible nitric oxide synthase (NOS-2) pathway [17]. The LPS insult is known to increase the level of proinflammatory cytokines [18, 19], which leads to excessive production of nitric oxide ( ∙ NO) via NOS-2 and increased production of prostanoids due to cyclooxygenase-2 (COX-2) induction as well as concomitant alternative mechanisms leading to endotoxemic multiorgan failure [20]. Since little is known regarding tissue-specific differences in changes of ROS/RNS balance in vivo as most studies focused on a single target organ or analysis of proinflammatory cytokines [19, 20], the tissue- and time-dependent changes in DHE oxidation products were supplemented by ex vivo detection of ∙ NO production using EPR spin trapping in the isolated aorta, lung, and liver tissues.…”

Body adiposity index in assessing the risk of type 2 diabetes mellitus development: the Baependi Heart Study

“…Diabetes Mellitus is a multifactorial metabolic disease associated with various conditions, including genetic predisposition, physical inactivity and mainly obesity. In fact, obesity is the second most important risk factor for various diseases [1] and its association with diabetes is very well established [2, 3]. As in the rest of the world, obesity has attracted attention in Brazil.…”

“…Comparisons between BAI and other adiposity indexes have been also explored [6, 7]. However, according to Alvim et al [2], ethnic differences may influence the discriminatory power of BAI, as well as several other anthropometric indices, in assessing the risk of T2DM. In agreement with this reality, our main interest is to investigate the influence of BAI on T2DM in a sample of the Brazilian population, after 5-year follow-up.…”