EDITOR'S PICK
A clearer understanding of glaucoma | Back to top
Glaucoma is one of the leading causes of vision loss and blindness worldwide. In glaucoma patients, the optic nerve, which relays information from the eye to the brain, is damaged, though the molecular cause of nerve damage is unclear. Dr. Simon John, from Tufts University in Boston, and colleagues specifically wanted to understand the earliest events that lead to optic nerve damage in glaucoma. Using a mouse model of the disease, the researchers showed that inflammatory immune cells called monocytes cross blood vessels and invade the optic nerve. Remarkably, mice treated with a single X-ray treatment in eyes prior to the onset of glaucoma were protected from developing the disease later in life. Through an unknown mechanism, the X-ray treatment prevented neuroinflammation and allowed mice to avoid glaucoma development, even in the presence of other risk factors. Continuing research by the John team will examine why the X-ray treatment effectively blocked glaucoma in the mouse model system and if this strategy might someday be adapted to prevent glaucoma in humans.
TITLE:
Radiation treatment inhibits monocyte entry into the optic nerve head and prevents neuronal damage in a mouse model of glaucoma
AUTHOR CONTACT:
Simon W.M. John
Howard Hughes Medical Institute, The Jackson Laboratory, 600 Main St., Bar Harbor, Maine 04609, USA. Phone: 207-288-6496; Fax: 207-288-6078; E-mail: simon.john@jax.org.
View this article at: http://www.jci.org/articles/view/61135?key=82201f32dfe421d1d337
CARDIOVASCULAR DISEASE
At the heart of it all: myosin regulatory protein key for cardiac muscle function | Back to top
A groundbreaking study by Ju Chen and colleagues at the University of California at San Diego sheds new light on the regulation of cardiac muscle contraction. The dynamic interaction of the proteins actin and myosin, which are key components of muscle fibers, is responsible for contractions. The binding of calcium to actin-bound regulatory proteins has long been regarded as the primary regulatory mechanism for muscle contraction. However, some data suggests that myosin regulatory proteins, such as ventricular myosin light chain-2 (MLC2v), might also contribute to the regulation of muscle contractions through unknown mechanisms.
The Chen team specifically examined the role of MLC2v phosphorylation on cardiac muscle. They show in cardiac tissue that MLC2v phosphorylation controls dynamic myosin and actin interactions. The team also extrapolates the molecular actions of MLC2v phosphorylation using computation models, which suggest that cross bridge attachment dynamics are controlled by MLC2v phosphorylation. Their model of MLC2v regulation of cardiac muscle contraction is supported by defects in the rate of twitch relaxation that they observed in a mouse model system in which MLC2v cannot be phosphorylated. Their study provides new appreciation for the role of myosin regulatory proteins in muscle contraction, and has important clinical implications for understanding heart disease.
TITLE:
Mouse and computational models link Mlc2v dephosphorylation to altered myosin kinetics in early cardiac disease
AUTHOR CONTACT:
Farah Sheikh
The University of California San Diego, La Jolla, CA, USA
Phone: 858-246-0754; E-mail: fasheikh@ucsd.edu
View this article at: http://www.jci.org/articles/view/61134?key=2d474e8f8bbd89c3c3e2
CARDIOVASCULAR DISEASE
A big role for microRNA in protecting heart tissue | Back to top
During a heart attack, a block in blood flow damages cardiac tissue. Though counterintuitive, significant tissue damage also occurs in response to the restoration of blood flow, known as ischemia/reperfusion injury, which activates stress pathways in the heart. This second wave of cardiac damage is caused by a many factors, including a disruption in the balance of calcium, which is a key regulator of heart contractions and cellular signaling. Dr. Eric Olson and his colleagues at the University of Texas Southwestern Medical Center in Dallas recently explored one of the causes of calcium overload during ischemia/reperfusion injury using a mouse model system. They suspected that regulatory RNA molecules known as microRNAs (miRNAs) may play a role in tissue damage in response to the restoration of blood flow to the heart. The team showed that miRNA-214, which is upregulated during the block in blood flow to the heart, helped protect tissue from ischemis/reperfusion injury. They found that mice that lack miRNA-214 lost heart contractility and showed an increase in fibrosis due to aberrant regulation of a key regulator of calcium influx. Their work has identified a new pathway that is important in regulating calcium homeostasis and protecting heart function.
TITLE:
microRNA-214 protects the heart from ischemic injury by controlling Ca2+ overload and cell death in mice
AUTHOR CONTACT:
Eric Olson
UT Southwestern Medical Center, Dallas, TX, USA
Phone: 214-648-1187; Fax: 214-648-1196; E-mail: Eric.Olson@utsouthwestern.edu
View this article at: http://www.jci.org/articles/view/59327?key=a681696f8fc27eb4f99a
CARDIOVASCULAR BIOLOGY
Endothelial Hypoxia Inducible Factor-2alpha (HIF-2α) regulates murine pathological angiogenesis and revascularization processes | Back to top
Understanding what triggers new blood vessels to grow has clinical implications for disorders characterized by restricted blood flow, such as macular degeneration and peripheral arterial disease, and for the growth of solid tumors, which require new blood flow to maintain aggressive growth. The development of new blood vessels, termed angiogenesis, is triggered in part by low oxygen levels. A transcription factor called Hypoxia Inducible Factor can respond to low oxygen and induce the expression of multiple genes required for angiogenesis.
A research group at the University of Pennsylvania in Philadelphia delved into the detailed mechanism of how the protein hypoxia inducible factor 2α (HIF-2 α) contributes to new blood vessel formation. Led by M. Celeste Simon, the team specifically disrupted the Hif-2α gene from mouse endothelial cells, which make up the walls of blood vessels, and observed an increase in blood vessel formation. However, the blood vessels that formed in the mouse model system had reduced blood flow and poor tissue oxygenation due to ineffective vessel remodeling. Their study distinguishes the role of Hif-2α from a related gene, Hif-1α, and suggest that these genes work synergistically to promote proper blood vessel formation.
TITLE:
Endothelial Hypoxia Inducible Factor-2alpha (HIF-2α) regulates murine pathological angiogenesis and revascularization processes
AUTHOR CONTACT:
M. Celeste Simon
University of Pennsylvania/HHMI, Philadelphia, PA, USA
Phone: 215-746-5532; Fax: 215-746-5511; E-mail: celeste2@mail.med.upenn.edu
View this article at: http://www.jci.org/articles/view/57322?key=ffe5c51b522aa2341952
VIROLOGY
Understanding how herpes simplex virus invades the central nervous system | Back to top
Herpes Simplex virus (HSV) 1 and 2 are the cause of cold sores and genital herpes, respectively, in humans. Even in the absence of outbreaks, remaining reservoirs of virus linger in the body. Both viruses can infect neurons and occasionally cause diseases such as encephalitis and meningitis, especially in people with compromised immune system. Søren Paludan and colleagues at Aarhus University in Denmark investigated what triggers increased susceptibility to HSV2 in the central nervous system using a mouse model system. The found that toll-like receptor 3 (TLR3) is critical for maintaining immunoprotective responses in the central nervous system and that mice lacking Tlr3 showed increased susceptibility to central nervous system complications following HSV-2 infection. Importantly, their work clarifies when and where TLR3 activity is necessary, and they demonstrate that TLR-3 elicits an interferon response in astrocytes following viral entry in the central nervous system. Their work clarifies the mechanisms whereby central nervous system diseases arise in HSV-infected individuals.
TITLE:
TLR3 deficiency renders astrocytes permissive to herpes simplex virus infection and facilitates establishment of CNS infection in mice
AUTHOR CONTACT:
Søren Paludan
University of Aarhus, Aarhus C, UNK, DNK
Phone: 45-8942-1767; Fax: 45-8619-6128; E-mail: srp@microbiology.au.dk
View this article at: http://www.jci.org/articles/view/60893?key=b1c8e06ace14d57b6549
IMMUNOLOGY
Immune response gone awry: treating autoimmune disorders with rituximab | Back to top
Rituximab is an antibody therapy that targets immune cells called B cells for destruction. The FDA has approved rituximab for treatment of specific disorders characterized by too many B cells, such as B cell lymphoma, or autoimmune disorders, such as rheumatoid arthritis. However, it has been unclear why some autoimmune patients show good long-term clinical response to rituximab while others do not.
In a clinical study of patients with anti-myelin-associated glycoprotein (MAG) neuropathy, an autoimmune disorder characterized by an immune system attack towards a protein expressed in the myelin sheath of peripheral nerves, Dr. Jan Lunemann and colleagues at the University of Zurich in Switzerland sought to discover why some patients respond well to rituximab. The team looked at memory B cell expansion before and after rituximab therapy in patients, and found that a good response was associated with depletion of non-circulating B cells and reconfiguration of B cell memory. The team suggests that non-responders may benefit from additional rituximab rounds of therapy to further reduce self-reactive B cells. Their findings support continued exploration of rituximab therapy for other autoimmune disorders where B cell depletion could alleviate symptoms.
TITLE:
Rituximab induces sustained reduction of pathogenic B cells in patients with peripheral nervous system autoimmunity
AUTHOR CONTACT:
Jan Lunemann
University of Zurich, Zurich, UNK, CHE
Phone: 41-44-635-3710; Fax: ; E-mail: jan.luenemann@uzh.ch
View this article at: http://www.jci.org/articles/view/58743?key=ff7ccbe1d4fa25c37448
METABOLIC DISEASE
Uncovering the links between diabetes and atherosclerosis | Back to top
Diabetic patients are at increased risk for cardiovascular disease and a hardening of blood vessel walls called atherosclerosis. One factor that drives atherosclerosis development in diabetes is abnormal blood cholesterol levels. Researchers suspect that a breakdown of LDL in early Type 2 diabetes by the low density lipoprotein receptor (LDLR) in liver leads to a compensatory increase in levels of very low density lipoprotein (VLDL).
The challenge of understanding the link between insulin and liver LDLR levels was addressed by Ding Ai and colleagues at the University of Texas Southwestern Medical Center in Dallas. Using several different mouse models, they showed that insulin receptor signaling via mTORC1 blocks LDLR breakdown by PCSK9. Thus LDLR is stabilized and more LDL is broken down, leading to disturbed cholesterol levels. Their results also help explain why rapamycin, a drug that inhibits mTORC1 and is used to suppress the immune system during transplantation, causes an increase in cholesterol levels.
TITLE:
Regulation of hepatic LDL receptors by mTORC1 and PCSK9
AUTHOR CONTACT:
Ding Ai
Columbia University Medical Center, new york, NY, USA
Phone: 212-305-5789; Fax: ; E-mail: da2424@columbia.edu
View this article at: http://www.jci.org/articles/view/61919?key=3d4f1e4a9bd3d7f71c60
NEUROBIOLOGY
A painful lesson: understanding what causes hypersensitivity to pain | Back to top
An increased sensitivity to pain, called hyperalgesia, can be debilitating for suffering patients. Hyperalgesia can be a complication of several disorders including stroke, fibromyalgia, diabetes, and neuropathic disorders. Inflammation, tissue damage, and nervous system disorders can all contribute to development of hyperalgesia, but the underlying molecular mechanisms are still unknown. Researchers at the Ernest Gallo Clinic in Emerville, CA set out to better understand the molecular cause of hyperalgesia. Led by Robert Messing, the team searched for the molecular target of PKCε, an enzyme that regulates hyperalgesia through a poorly understood mechanism. The research team identified a sodium channel that is targeted by PKCε in sensory neurons called nociceptors. Further, they showed depleting these specific sodium channels from nociceptors in a mouse model system blocked the development of hyperalgesia. These results provide new evidence for the molecular causes of hyperalgesia and suggest that targeting this pathway may be an effective strategy for designing new therapeutics to treat hyperalgesia.
TITLE:
PKC epsilon phosphorylation of NaV1.8 increases sodium channel function and produces mechanical hyperalgesia in mice
AUTHOR CONTACT:
Robert Messing
Univ. of Calif. San Francisco, Emeryville, CA, USA
Phone: 510-985-3950; Fax: 510-985-3101; E-mail: romes@gallo.ucsf.edu
View this article at: http://www.jci.org/articles/view/61934?key=df6009bb3364cd6c8a9b
ONCOLOGY
Learning from mistakes: why a promising therapy for follicular lymphoma failed | Back to top
Follicular lymphoma is a cancer characterized by abnormal proliferation of immune cells called B cells. One therapeutic strategy, Interleukin (IL) -12 therapy, was predicted to increase the clearing of malignant B cells by activating natural killer (NK) cells and T cells, components of the immune system. Unfortunately, this strategy had very limited efficacy in a previously conducted clinical trial of follicular lymphoma patients. Dr. Stephen Ansell and colleagues at the Mayo Clinic in Rochester, MN wanted to understand why IL-12 therapy had failed. They found that activation of the IL-12 pathway exhausted T cell populations through a previously unknown mechanism, rather than stimulating clearance of tumor cells. When the therapy was designed, it was hoped that IL-12 would promote T cell responsiveness through the production of interferon gamma (IFN-γ), which stimulates immune system activity. The research team found that instead T cell exhaustion is induced in patients by IL-12-induced expression of TIM-3, a family member of T-cell immunoglobulin and mucin domain proteins, that negatively regulates immune response. Thus, their study explains why IL-12 therapy was ineffective in treating follicular lymphoma patients and highlights the importance of TIM-3 downstream of the IL-12 pathway.
TITLE:
IL-12 upregulates TIM-3 expression and induces T cell exhaustion in patients with follicular B cell non-Hodgkin lymphoma
AUTHOR CONTACT:
Stephen Ansell
Mayo Clinic, Rochester, , USA
Phone: 507-284-3805; Fax: ; E-mail: ansell.stephen@mayo.edu
View this article at: http://www.jci.org/articles/view/59806?key=508276a4858aa2a078bc
Journal
Journal of Clinical Investigation