Min Zhu

Self-resolving inflammatory exudates and lipid mediator metabolomics recently uncovered a new family of potent anti-inflammatory and proresolving mediators biosynthesized by macrophages (MΦs), denoted maresins. Here we determined that maresin 1 (MaR1) produced by human MΦs from endogenous docosahexaenoic acid (DHA) matched synthetic 7R,14S-dihydroxydocosa-4Z,8E,10E,12Z,16Z,19Z-hexaenoic acid. The MaR1 alcohol groups and Z/E geometry of conjugated double bonds were matched using isomers prepared by total organic synthesis. MaR1's potent defining actions were confirmed with synthetic MaR1, i.e., limiting polymorphonuclear neutrophil (PMN) infiltration in murine peritonitis (ng/mouse range) as well as enhancing human macrophage uptake of apoptotic PMNs. At 1 nM, MaR1 was slightly more potent than resolvin D1 in stimulating human MΦ efferocytosis, an action not shared by leukotriene B(4). MaR1 also accelerated surgical regeneration in planaria, increasing the rate of head reappearance. On injury of planaria, MaR1 was biosynthesized from deuterium-labeled (d(5))-DHA that was blocked with lipoxygenase (LOX) inhibitor. MaR1 dose-dependently inhibited TRPV1 currents in neurons, blocked capsaicin (100 nM)-induced inward currents (IC(50) 0.49±0.02 nM), and reduced both inflammation- and chemotherapy-induced neuropathic pain in mice. These results demonstrate the potent actions of MaR1 in regulating inflammation resolution, tissue regeneration, and pain resolution. These findings suggest that chemical signals are shared in resolution cellular trafficking, a key process in tissue regeneration. Moreover, immunoresolvents of the innate immune response, such as MaR1, offer new opportunities for assessing MΦs and their local DHA metabolome in the return to tissue homeostasis.

Patients with type 2 diabetes (T2D) have disease-associated changes in B-cell function, but the role these changes play in disease pathogenesis is not well established. Data herein show B cells from obese mice produce a proinflammatory cytokine profile compared with B cells from lean mice. Complementary in vivo studies show that obese B cell-null mice have decreased systemic inflammation, inflammatory B- and T-cell cytokines, adipose tissue inflammation, and insulin resistance (IR) compared with obese WT mice. Reduced inflammation in obese/insulin resistant B cell-null mice associates with an increased percentage of anti-inflammatory regulatory T cells (Tregs). This increase contrasts with the sharply decreased percentage of Tregs in obese compared with lean WT mice and suggests that B cells may be critical regulators of T-cell functions previously shown to play important roles in IR. We demonstrate that B cells from T2D (but not non-T2D) subjects support proinflammatory T-cell function in obesity/T2D through contact-dependent mechanisms. In contrast, human monocytes increase proinflammatory T-cell cytokines in both T2D and non-T2D analyses. These data support the conclusion that B cells are critical regulators of inflammation in T2D due to their direct ability to promote proinflammatory T-cell function and secrete a proinflammatory cytokine profile. Thus, B cells are potential therapeutic targets for T2D.

BACKGROUND: Cardiac dysfunction is a major component of sepsis-induced multiorgan failure in critical care units. Changes in cardiac autophagy and its role during sepsis pathogenesis have not been clearly defined. Targeted autophagy-based therapeutic approaches for sepsis are not yet developed. METHODS: Beclin-1-dependent autophagy in the heart during sepsis and the potential therapeutic benefit of targeting this pathway were investigated in a mouse model of lipopolysaccharide (LPS)-induced sepsis. RESULTS: LPS induced a dose-dependent increase in autophagy at low doses, followed by a decline that was in conjunction with mammalian target of rapamycin activation at high doses. Cardiac-specific overexpression of Beclin-1 promoted autophagy, suppressed mammalian target of rapamycin signaling, improved cardiac function, and alleviated inflammation and fibrosis after LPS challenge. Haplosufficiency for beclin 1 resulted in opposite effects. Beclin-1 also protected mitochondria, reduced the release of mitochondrial danger-associated molecular patterns, and promoted mitophagy via PTEN-induced putative kinase 1-Parkin but not adaptor proteins in response to LPS. Injection of a cell-permeable Tat-Beclin-1 peptide to activate autophagy improved cardiac function, attenuated inflammation, and rescued the phenotypes caused by beclin 1 deficiency in LPS-challenged mice. CONCLUSIONS: These results suggest that Beclin-1 protects the heart during sepsis and that the targeted induction of Beclin-1 signaling may have important therapeutic potential.

Zoning in on liver growth For organ homeostasis or regrowth after injury or disease, one or more stem cell populations is needed to rebuild lost tissue. There is considerable debate about the source of new cells in the liver. Two groups now identify the source of new hepatocytes (see the Perspective by Andersson). Although the liver may seem to lack major variation across its structure, its lobule is organized into concentric zones where hepatocytes express different metabolic enzymes. Wei et al. sought to systematically define the source of new liver cells by comparing 14 fate-mapping mice that label different liver cell types. They found that different regions of the liver lobule exhibit differences in hepatocyte turnover, with zone 2 representing a primary source of new hepatocytes during homeostasis and regeneration. Similarly, He et al. designed a genetic approach to record cell proliferation in vivo with high spatial and temporal resolution to enable continuous recording of proliferative events of any specific cell type at the whole-cell population level. Using this method, they identified zone 2 as having the highest proliferative activity and contributing the most to liver regrowth. These findings have implications for the cellular basis of chronic disease pathogenesis, cancer development, and regenerative medicine strategies. Science , this issue p. eabb1625 , p. eabc4346 ; see also p. 887

Maresins are produced by macrophages from docosahexaenoic acid (DHA) and exert potent proresolving and tissue homeostatic actions. Maresin 1 (MaR1; 7 R ,14 S ‐dihydroxy‐docosa‐4 Z ,8 E ,10 E ,12 Z ,16 Z ,19 Z ‐hexaenoic acid) is the first identified maresin. Here, we investigate formation, stereochemistry, and precursor role of 13,14‐epoxy‐docosahexaenoic acid, an intermediate in MaR1 biosynthesis. The 14‐lipoxygenation of DHA by human macrophage 12‐lipoxygenase (hm12‐LOX) gave 14‐hydro(peroxy)‐docosahexaenoic acid (14‐HpDHA), as well as several dihydroxy‐docosahexaenoic acids, implicating an epoxide intermediate formation by this enzyme. Using a stereo‐controlled synthesis, enantiomerically pure 13 S ,14 S ‐epoxy‐docosa‐4 Z ,7 Z ,9 E ,11 E ,16 Z ,19 Z ‐hexaenoic acid (13 S ,14 S ‐epoxy‐DHA) was prepared, and its stereochemistry was confirmed by NMR spectroscopy. When this 13 S ,14 S ‐epoxide was incubated with human macrophages, it was converted to MaR1. The synthetic 13 S ,14 S ‐epoxide inhibited leukotriene B 4 (LTB 4 ) formation by human leukotriene A 4 hydrolase (LTA 4 H) ~40% ( P <0.05) to a similar extent as LTA4 (~50%, P <0.05) but was not converted to MaR1 by this enzyme. 1 3S ,14 S ‐epoxy‐DHA also reduced (~60%; P <0.05) arachidonic acid conversion by hm12‐LOX and promoted conversion of M1 macrophages to M2 phenotype, which produced more MaR1 from the epoxide than M1. Together, these findings establish the biosynthesis of the 13 S ,14 S ‐epoxide, its absolute stereochemistry, its precursor role in MaR1 biosynthesis, and its own intrinsic bioactivity. Given its actions and role in MaR1 biosynthesis, this epoxide is now termed 13,14‐epoxy‐maresin (13,14‐eMaR) and exhibits new mechanisms in resolution of inflammation in its ability to inhibit proinflammatory mediator production by LTA4 hydrolase and to block arachidonate conversion by human 12‐LOX rather than merely terminating phagocyte involvement.—Dalli, J., Zhu, M., Vlasenko, N. A., Deng, B., Haeggström, J. Z., Petasis, N. A., Serhan, C. N. The novel 13 S ,14 S ‐epoxy‐maresin is converted by human macrophages to maresin 1 (MaR1), inhibits leukotriene A4 hydrolase (LTA4H) and shifts macrophage phenotype. FASEB J. 27, 2573–2583 (2013). www.fasebj.org