Alveolar inflammation is a hallmark of acute lung injury (ALI), and its clinical correlate is acute respiratory distress syndrome-and it is as a result of interactions between alveolar type II cells (ATII) and alveolar macrophages (AM). In the setting of acute injury, the microenvironment of the intra-alveolar space is determined in part by metabolites and cytokines and is known to shape the AM phenotype. In response to ALI, increased glycolysis is observed in AT II cells, mediated by the transcription factor hypoxia-inducible factor (HIF) 1α, which has been shown to decrease inflammation. We hypothesized that in acute lung injury, lactate, the end product of glycolysis, produced by ATII cells shifts AMs toward an anti-inflammatory phenotype, thus mitigating ALI. We found that local intratracheal delivery of lactate improved ALI in two different mouse models. Lactate shifted cytokine expression of murine AMs toward increased IL-10, while decreasing IL-1 and IL-6 expression. Mice with ATII-specific deletion of Hif1a and mice treated with an inhibitor of lactate dehydrogenase displayed exacerbated ALI and increased inflammation with decreased levels of lactate in the bronchoalveolar lavage fluid; however, all those parameters improved with intratracheal lactate. When exposed to LPS (to recapitulate an inflammatory stimulus as it occurs in ALI), human primary AMs co-cultured with alveolar epithelial cells had reduced inflammatory responses. Taken together, these studies reveal an innate protective pathway, in which lactate produced by ATII cells shifts AMs toward an anti-inflammatory phenotype and dampens excessive inflammation in ALI.
© 2023 Federation of American Societies for Experimental Biology.

Host-directed therapies are gaining considerable impetus because of the emergence of drug-resistant strains of pathogens due to antibiotic therapy. Therefore, there is an urgent need to exploit alternative and novel strategies directed at host molecules to successfully restrict infections. The C-type lectin receptor CLEC4E and Toll-like receptor TLR4 expressed by host cells are among the first line of defense in encountering pathogens. Therefore, we exploited signaling of macrophages through CLEC4E in association with TLR4 agonists (C4.T4) to control the growth of Mycobacterium tuberculosis (Mtb). We observed significant improvement in host immunity and reduced bacterial load in the lungs of Mtb-infected mice and guinea pigs treated with C4.T4 agonists. Further, intracellular killing of Mtb was achieved with a 10-fold lower dose of isoniazid or rifampicin in conjunction with C4.T4 than the drugs alone. C4.T4 activated MYD88, PtdIns3K, STAT1 and RELA/NFKB, increased lysosome biogenesis, decreased Il10 and Il4 gene expression and enhanced macroautophagy/autophagy. Macrophages from autophagy-deficient (atg5 knockout or Becn1 knockdown) mice showed elevated survival of Mtb. The present findings also unveiled the novel role of CLEC4E in inducing autophagy through MYD88, which is required for control of Mtb growth. This study suggests a unique immunotherapeutic approach involving CLEC4E in conjunction with TLR4 to restrict the survival of Mtb through autophagy.
3MA: 3 methyladenine; AO: acridine orange; Atg5: autophagy related 5; AVOs: acidic vesicular organelles; BECN1: beclin 1, autophagy related; BMDMs: bone marrow derived macrophages; bw: body weight; C4.T4: agonists of CLEC4E (C4/TDB) and TLR4 (T4/ultra-pure-LPS); CFU: colony forming unit; CLEC4E/Mincle: C-type lectin domain family 4, member e; CLR: c-type lectin receptor; INH: isoniazid; LAMP1: lysosomal-associated membrane protein 1; MφC4.T4: Mtb-infected C4.T4 stimulated macrophages; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MDC: monodansylcadaverine; MTOR: mechanistic target of rapamycin kinase; MYD88: myeloid differentiation primary response 88; NFKB: nuclear factor of kappa light polypeptide gene enhance in B cells; NLR: NOD (nucleotide-binding oligomerization domain)-like receptors; PFA: paraformaldehyde; PPD: purified protein derivative; PtdIns3K: class III phosphatidylinositol 3-kinase; RELA: v-rel reticuloendotheliosis viral oncogene homolog A (avian); RIF: rifampicin; RLR: retinoic acid-inducible gene-I-like receptors; TDB: trehalose-6,6´-dibehenate; TLR4: toll-like receptor 4; Ultra-pure-LPS: ultra-pure lipopolysaccharide-EK; V-ATPase: vacuolar-type H+ ATPase.

Shiga toxin (Stx) produced by enterohemorrhagic E. coli produces hemolytic uremic syndrome and encephalopathies in patients, which can lead to either reversible or permanent neurological abnormalities, or even fatal cases depending on the degree of intoxication. It has been observed that the inflammatory component plays a decisive role in the severity of the disease. Therefore, the objective of this work was to evaluate the behavior of microglial cell primary cultures upon Stx2 exposure and heat shock or lipopolysaccharide challenges, as cues which modulate cellular environments, mimicking fever and inflammation states, respectively. In these contexts, activated microglial cells incorporated Stx2, increased their metabolism, phagocytic capacity, and pro-inflammatory profile. Stx2 uptake was associated to receptor globotriaosylceramide (Gb3)-pathway. Gb3 had three clearly distinguishable distribution patterns which varied according to different contexts. In addition, toxin uptake exhibited both a Gb3-dependent and a Gb3-independent binding depending on those contexts. Altogether, these results suggest a fundamental role for microglial cells in pro-inflammatory processes in encephalopathies due to Stx2 intoxication and highlight the impact of environmental cues.
Copyright © 2020 Berdasco, Duhalde Vega, Rosato-Siri and Goldstein.

Transforming growth factor-β (TGF-β) regulates reciprocal regulatory T cell (T reg) and T helper 17 (Th17) differentiation, the underlying mechanism of which is still not understood. Here, we report that tripartite motif-containing 33 (Trim33), a modulator of TGF-β signaling that associates with Smad2, regulates the proinflammatory function of Th17 cells. Trim33 deficiency in T cells ameliorated an autoimmune disease in vivo. Trim33 was required for induction in vitro of Th17, but not T reg cells. Moreover, Smad4 and Trim33 play contrasting roles in the regulation of IL-10 expression; loss of Trim33 enhanced IL-10 production. Furthermore, Trim33 was recruited to the Il17a and Il10 gene loci, dependent on Smad2, and mediated their chromatin remodeling during Th17 differentiation. Trim33 thus promotes the proinflammatory function of Th17 cells by inducing IL-17 and suppressing IL-10 expression.
© 2018 Tanaka et al.

High salt consumption has since long been associated with elevated blood pressure and cardiovascular disease. Recently, mouse studies suggested that a high dietary salt intake exacerbates the clinical manifestations of autoimmunity. Using naïve cells ex vivo after pre-exposure of mice to high salt intake, we showed that increased salt exposure affects the viability and effector functions of immune cells. CD4+ T-cells evidenced a pro-inflammatory phenotype characterized by increased secretion of IFNγ and IL-17A, when exposed to high salt concentrations in vitro. Interestingly, this phenotype was associated with osmotic pressure, as replacing salt for d-mannitol resulted in similar observations. However, high salt intake did not alter the development of T-cell-dependent autoimmunity. Instead, recruitment of peritoneal macrophages was increased in mice pre-exposed to high salt concentrations. These cells had an increased production of both TNFα and IL-10, suggesting that salt stimulates expansion and differentiation of different subsets of macrophages. Moreover, mice pre-exposed to high salt intake developed exacerbated symptoms of colitis, when induced by dextran sulphate sodium. The aggravated colitis in salt-exposed animals was associated with a higher frequency of CD4+ T-cells and CD11b+ CD64+ macrophages producing TNFα. These phenotypes correlated with elevated titres of faecal IgA and higher lymphocytic cellularity in the colon, mesenteric lymph nodes and spleen. In conclusion, we report here that high salt intake affects both lymphoid and myeloid cells ex vivo. However, the effects of high salt intake in vivo seem less pronounced in terms of CD4+ T-cell responses, whereas macrophage-dependent pathologies are significantly influenced.
© 2018 John Wiley & Sons Ltd.