A cell-type-specific role for murine Commd1 in liver inflammation

The transcription factor NF-kappaB plays a critical role in the inflammatory response and it has been implicated in various diseases, including non-alcoholic fatty liver disease (NAFLD). Although transient NF-kappaB activation may protect tissues from stress, a prolonged NF-kappaB activation can have a detrimental effect on tissue homeostasis and therefore accurate termination is crucial. Copper Metabolism MURR1 Domain-containing 1 (COMMD1), a protein with functions in multiple pathways, has been shown to suppress NF-kappaB activity. However, its action in controlling liver inflammation has not yet been investigated. To determine the cell-type-specific contribution of Commd1 to liver inflammation, we used hepatocyte and myeloid-specific Commd1-deficient mice. We also used a mouse model of NAFLD to study low-grade chronic liver inflammation: we fed the mice a high fat, high cholesterol (HFC) diet, which results in hepatic lipid accumulation accompanied by liver inflammation. Depletion of hepatocyte Commd1 resulted in elevated levels of the NF-kappaB transactivation subunit p65 (RelA) but, surprisingly, the level of liver inflammation was not aggravated. In contrast, deficiency of myeloid Commd1 exacerbated diet-induced liver inflammation. Unexpectedly we observed that hepatic and myeloid Commd1 deficiency in the mice both augmented hepatic lipid accumulation. The elevated levels of proinflammatory cytokines in myeloid Commd1-deficient mice might be responsible for the increased level of steatosis. This increase was not seen in hepatocyte Commd1-deficient mice, in which increased lipid accumulation appeared to be independent of inflammation. Our mouse models demonstrate a cell-type-specific role for Commd1 in suppressing liver inflammation and in the progression of NAFLD

TLR9 and beclin 1 crosstalk regulates muscle AMPK activation in exercise.

The activation of adenosine monophosphate-activated protein kinase (AMPK) in skeletal muscle coordinates systemic metabolic responses to exercise. Autophagy-a lysosomal degradation pathway that maintains cellular homeostasis-is upregulated during exercise, and a core autophagy protein, beclin 1, is required for AMPK activation in skeletal muscle. Here we describe a role for the innate immune-sensing molecule Toll-like receptor 9 (TLR9), and its interaction with beclin 1, in exercise-induced activation of AMPK in skeletal muscle. Mice that lack TLR9 are deficient in both exercise-induced activation of AMPK and plasma membrane localization of the GLUT4 glucose transporter in skeletal muscle, but are not deficient in autophagy. TLR9 binds beclin 1, and this interaction is increased by energy stress (glucose starvation and endurance exercise) and decreased by a BCL2 mutation that blocks the disruption of BCL2-beclin 1 binding. TLR9 regulates the assembly of the endolysosomal phosphatidylinositol 3-kinase complex (PI3KC3-C2)-which contains beclin 1 and UVRAG-in skeletal muscle during exercise, and knockout of beclin 1 or UVRAG inhibits the cellular AMPK activation induced by glucose starvation. Moreover, TLR9 functions in a muscle-autonomous fashion in ex vivo contraction-induced AMPK activation, glucose uptake and beclin 1-UVRAG complex assembly. These findings reveal a heretofore undescribed role for a Toll-like receptor in skeletal-muscle AMPK activation and glucose metabolism during exercise, as well as unexpected crosstalk between this innate immune sensor and autophagy proteins

Clearance of p16Ink4a-positive senescent cells delays ageing-associated disorders

Contains fulltext : 96729.pdf (publisher's version ) (Closed access)Advanced age is the main risk factor for most chronic diseases and functional deficits in humans, but the fundamental mechanisms that drive ageing remain largely unknown, impeding the development of interventions that might delay or prevent age-related disorders and maximize healthy lifespan. Cellular senescence, which halts the proliferation of damaged or dysfunctional cells, is an important mechanism to constrain the malignant progression of tumour cells. Senescent cells accumulate in various tissues and organs with ageing and have been hypothesized to disrupt tissue structure and function because of the components they secrete. However, whether senescent cells are causally implicated in age-related dysfunction and whether their removal is beneficial has remained unknown. To address these fundamental questions, we made use of a biomarker for senescence, p16(Ink4a), to design a novel transgene, INK-ATTAC, for inducible elimination of p16(Ink4a)-positive senescent cells upon administration of a drug. Here we show that in the BubR1 progeroid mouse background, INK-ATTAC removes p16(Ink4a)-positive senescent cells upon drug treatment. In tissues--such as adipose tissue, skeletal muscle and eye--in which p16(Ink4a) contributes to the acquisition of age-related pathologies, life-long removal of p16(Ink4a)-expressing cells delayed onset of these phenotypes. Furthermore, late-life clearance attenuated progression of already established age-related disorders. These data indicate that cellular senescence is causally implicated in generating age-related phenotypes and that removal of senescent cells can prevent or delay tissue dysfunction and extend healthspan

Increased expression of BubR1 protects against aneuploidy and cancer and extends healthy lifespan

Item does not contain fulltextThe BubR1 gene encodes for a mitotic regulator that ensures accurate segregation of chromosomes through its role in the mitotic checkpoint and the establishment of proper microtubule-kinetochore attachments. Germline mutations that reduce BubR1 abundance cause aneuploidy, shorten lifespan and induce premature ageing phenotypes and cancer in both humans and mice. A reduced BubR1 expression level is also a feature of chronological ageing, but whether this age-related decline has biological consequences is unknown. Using a transgenic approach in mice, we show that sustained high-level expression of BubR1 preserves genomic integrity and reduces tumorigenesis, even in the presence of genetic alterations that strongly promote aneuplodization and cancer, such as oncogenic Ras. We find that BubR1 overabundance exerts its protective effect by correcting mitotic checkpoint impairment and microtubule-kinetochore attachment defects. Furthermore, sustained high-level expression of BubR1 extends lifespan and delays age-related deterioration and aneuploidy in several tissues. Collectively, these data uncover a generalized function for BubR1 in counteracting defects that cause whole-chromosome instability and suggest that modulating BubR1 provides a unique opportunity to extend healthy lifespan