Articles in 2011

Wound healing involves a transient regeneration of tissue, but, if this process continues unabated, pathology occurs in the form of fibrosis, which can prevent normal organ function and even death. Derek Mann and his colleagues have found that serotonin-responsive profibrogenic hepatic stellate cells inhibit the growth of neighboring liver cells during the termination phase of liver injury. They also found that inhibiting serotonin signaling during established disease improved liver fibrosis in various mouse models of liver injury.

Timothy syndrome is a neurodevelopmental disease that includes autism-like features. Using iPS-derived neurons from individuals with Timothy syndrome, Ricardo Dolmetsch and his colleagues identify changes in cortical neuron fate and neurotransmitter expression that may begin to explain the neural mechanisms that underlie this disorder.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that primarily affects motor neurons. Now, Valentin Gribkoff and his colleagues show some preliminary evidence that the drug dexpramipexole may have clinical activity in a small placebo-controlled trial in patients with ALS.

This report identifies oncogenic fusions in individuals with breast cancer involving the genes encoding NOTCH and MAST, recurring in approximately 5–7% of studied cases. The fusions show growth-promoting properties that suggest that they may represent targetable events in a subset of people with breast cancer.

Bone marrow-derived mesenchymal stem cells (BMMSCs) have so far failed to live up to their potential as a treatment for the repair of large bone defects. Songtao Shi and his colleagues now show that this may be due to their apoptosis mediated by resident T cells in the wound as a result of excess IFN-γ and TNF-α signaling. They show that reducing the levels of these cytokines, including through the local administration of aspirin, markedly increases the survival of implanted BMMSCs and improves bone wound healing in a mouse model.

Polly Matzinger and her colleagues have shown that in the absence of B cells, and in the presence of the microbiota, the intestinal epithelium launches its own immune defense mechanisms. However, this comes at the expense of metabolic programs involved in fat absorption by the gut. These results could explain the lipid malabsorption often seen in humans with common variable immunodeficiency or with HIV infection.

Glycoconjugate vaccines—such as those targeting some bacteria—couple a glycan to a protein to provide T cell help to B cells and induce polysaccharide-specific IgGs. T cell help has been thought to be conferred by recognition of the protein portion by T cells. Dennis Kasper and his colleagues now report that a glycan-peptide conjugate can induce T cells specific for the glycan moiety, which could help inform future glycoconjugate vaccine development.

This report identifies a new contribution of members of the miR-200 family to tumorigenesis. miR-200a and miR-141 specifically regulate p38α, contributing to the cellular modulation of oxidative stress responses. In this role, the miRs can accelerate ovarian tumorigenesis but also endow cancer cells with increased sensitivity to ROS-inducing chemotherapy. This two-part effect is reflected on the distinct association of the miRs with patient survival and may be informative for treatment decisions.

Although maturation of dendritic cells can drive autoimmune responses in mice, it remains unclear whether intrinsic factors hold dendritic cells in a resting state. Pamela Ohashi and her colleagues identify a repressive mechanism requiring expression of nuclear factor-κB1 in dendritic cells. Loss of nuclear factor-κB1 results in CD8⁺ T cell activation, TNF-α production and autoimmune diabetes in mice.

Raf kinase activity is deregulated in cancers and is thought to promote tumor growth by inducing proliferation signaling through MEK/Erk. This report identifies a new role for c-Raf independent of MEK/Erk and relying on phosphorylation of Ser338. Phospho–C-Raf interacts with the mitotic kinases Aurora-A and Plk1, activating the latter to promote mitotic progression and increase cell division, and this pathway is a crucial mediator for the protumorigenic effect of c-Raf in vivo.

The enzyme argininosuccinate lyase (ASL) generates the amino acid arginine, the precursor to both urea and nitric oxide. However, arginine supplementation is not sufficient to correct all of the symptoms of individuals with a congenital deficiency of this enzyme. Ayelet Erez et al. explain this paradox by showing that ASL has a role in nitric oxide synthesis that is independent of its catalytic activity and provide evidence that therapy with agents boosting nitric oxide levels might be beneficial in ASL-deficient individuals.

It is well regarded that insulin receptor signaling in the liver is key to proper metabolic control. Reza Zarnegar and his colleagues now show that the hepatocyte growth factor receptor, Met, physically interacts with the insulin receptor signaling complex, potentiating the latter's signaling. They also show that Met signaling restores insulin responsiveness in a mouse model of insulin resistance, suggesting a potentially new therapeutic avenue to treat prediabetes.

The hormone aldosterone can damage the heart after myocardial infarction, such that drugs that inhibit its action are often prescribed. B. Julie He et al. now uncover a new pathway underlying the detrimental effects of aldosterone action: oxidation of the enzyme Ca²⁺/calmodulin-dependent protein kinase II leads to its activation and increased expression of the metalloprotease MMP9 in cardiac muscle cells, thereby promoting cardiac rupture.