Myeloid-derived miR-6236 potentiates adipocyte insulin signaling and prevents hyperglycemia during obesity.

Adipose tissue macrophages (ATMs) influence obesity-associated metabolic dysfunction, but the mechanisms by which they do so are not well understood. We show that miR-6236 is a bona fide miRNA that is secreted by ATMs during obesity. Global or myeloid cell-specific deletion of miR-6236 aggravates obesity-associated adipose tissue insulin resistance, hyperglycemia, hyperinsulinemia, and hyperlipidemia. miR-6236 augments adipocyte insulin sensitivity by inhibiting translation of negative regulators of insulin signaling, including PTEN. The human genome harbors a miR-6236 homolog that is highly expressed in the serum and adipose tissue of obese people. hsa-MIR-6236 expression negatively correlates with hyperglycemia and glucose intolerance, and positively correlates with insulin sensitivity. Together, our findings establish miR-6236 as an ATM-secreted miRNA that potentiates adipocyte insulin signaling and protects against metabolic dysfunction during obesity.

RIPK1 activates distinct gasdermins in macrophages and neutrophils upon pathogen blockade of innate immune signaling.

Injection of effector proteins to block host innate immune signaling is a common strategy used by many pathogenic organisms to establish an infection. For example, pathogenic Yersinia species inject the acetyltransferase YopJ into target cells to inhibit NF-κB and MAPK signaling. To counteract this, detection of YopJ activity in myeloid cells promotes the assembly of a RIPK1-caspase-8 death-inducing platform that confers antibacterial defense. While recent studies revealed that caspase-8 cleaves the pore-forming protein gasdermin D to trigger pyroptosis in macrophages, whether RIPK1 activates additional substrates downstream of caspase-8 to promote host defense is unclear. Here, we report that the related gasdermin family member gasdermin E (GSDME) is activated upon detection of YopJ activity in a RIPK1 kinase-dependent manner. Specifically, GSDME promotes neutrophil pyroptosis and IL-1ß release, which is critical for anti-Yersinia defense. During in vivo infection, IL-1ß neutralization increases bacterial burden in wild-type but not Gsdme-deficient mice. Thus, our study establishes GSDME as an important mediator that counteracts pathogen blockade of innate immune signaling.

Rab6-dependent retrograde traffic of LAT controls immune synapse formation and T cell activation.

The adapter molecule linker for activation of T cells (LAT) orchestrates the formation of signalosomes upon T cell receptor (TCR) stimulation. LAT is present in different intracellular pools and is dynamically recruited to the immune synapse upon stimulation. However, the intracellular traffic of LAT and its function in T lymphocyte activation are ill defined. We show herein that LAT, once internalized, transits through the Golgi-trans-Golgi network (TGN), where it is repolarized to the immune synapse. This retrograde transport of LAT depends on the small GTPase Rab6 and the target soluble N-ethylmaleimide-sensitive factor attachment protein receptor (t-SNARE) Syntaxin-16, two regulators of the endosome-to-Golgi/TGN retrograde transport. We also show in vitro in Syntaxin-16- or Rab6-silenced human cells and in vivo in CD4+ T lymphocytes of the Rab6 knockout mouse that this retrograde traffic controls TCR stimulation. These results establish that the retrograde traffic of LAT from the plasma membrane to the Golgi-TGN controls the polarized delivery of LAT at the immune synapse and T lymphocyte activation.

The TAM family receptor tyrosine kinase TYRO3 is a negative regulator of type 2 immunity.

Host responses against metazoan parasites or an array of environmental substances elicit type 2 immunity. Despite its protective function, type 2 immunity also drives allergic diseases. The mechanisms that regulate the magnitude of the type 2 response remain largely unknown. Here, we show that genetic ablation of a receptor tyrosine kinase encoded byTyro3in mice or the functional neutralization of its ortholog in human dendritic cells resulted in enhanced type 2 immunity. Furthermore, the TYRO3 agonist PROS1 was induced in T cells by the quintessential type 2 cytokine, interleukin-4. T cell-specificPros1knockouts phenocopied the loss ofTyro3 Thus, a PROS1-mediated feedback from adaptive immunity engages a rheostat, TYRO3, on innate immune cells to limit the intensity of type 2 responses.

Pharmacokinetic aspects of naloxone-precipitated morphine withdrawal in male and female prepubertal mice.

It has been shown that the expression of the morphine (MOR) withdrawal syndrome precipitated by naloxone (NAL) is more intense in male mice than in females, but the reasons for this phenomenon remain uncertain. The purpose of the present study was to evaluate whether this sexual dimorphism might be due to differences in MOR and/or NAL plasma levels after a chronic treatment with MOR. Prepubertal Swiss male and female mice were rendered dependent by intraperitoneal (i.p.) injection of MOR (2 mg/kg), twice daily for 9 days. On day 10 dependent mice received NAL (6 mg/kg, i.p.) 60 min after MOR injection. Blood samples were taken at different times in order to determine MOR and NAL plasma levels by gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC), respectively. Pharmacokinetic analysis showed no differences between male and female mice either for MOR or for NAL. In conclusion, although males and females respond differentially to NAL-precipitated withdrawal, this dimorphic behavior would not be influenced by a pharmacokinetic factor.