Gene expression and matrix turnover in overused and damaged tendons

Chronic, painful conditions affecting tendons, frequently known as tendinopathy, are very common types of sporting injury. The tendon extracellular matrix is substantially altered in tendinopathy, and these changes are thought to precede and underlie the clinical condition. The tendon cell response to repeated minor injuries or “overuse” is thought to be a major factor in the development of tendinopathy. Changes in matrix turnover may also be effected by the cellular response to physical load, altering the balance of matrix turnover and changing the structure and composition of the tendon. Matrix turnover is relatively high in tendons exposed to high mechanical demands, such as the supraspinatus and Achilles, and this is thought to represent either a repair or tissue maintenance function. Metalloproteinases are a large family of enzymes capable of degrading all of the tendon matrix components, and these are thought to play a major role in the degradation of matrix during development, adaptation and repair. It is proposed that some metalloproteinase enzymes are required for the health of the tendon, and others may be damaging, leading to degeneration of the tissue. Further research is required to investigate how these enzyme activities are regulated in tendon and altered in tendinopathy. A profile of all the metalloproteinases expressed and active in healthy and degenerate tendon is required and may lead to the development of new drug therapies for these common and debilitating sports injuries

The ERK and JNK pathways in the regulation of metabolic reprogramming.

Most tumor cells reprogram their glucose metabolism as a result of mutations in oncogenes and tumor suppressors, leading to the constitutive activation of signaling pathways involved in cell growth. This metabolic reprogramming, known as aerobic glycolysis or the Warburg effect, allows tumor cells to sustain their fast proliferation and evade apoptosis. Interfering with oncogenic signaling pathways that regulate the Warburg effect in cancer cells has therefore become an attractive anticancer strategy. However, evidence for the occurrence of the Warburg effect in physiological processes has also been documented. As such, close consideration of which signaling pathways are beneficial targets and the effect of their inhibition on physiological processes are essential. The MAPK/ERK and MAPK/JNK pathways, crucial for normal cellular responses to extracellular stimuli, have recently emerged as key regulators of the Warburg effect during tumorigenesis and normal cellular functions. In this review, we summarize our current understanding of the roles of the ERK and JNK pathways in controlling the Warburg effect in cancer and discuss their implication in controlling this metabolic reprogramming in physiological processes and opportunities for targeting their downstream effectors for therapeutic purposes.Brunel Research Initiative & Enterprise Fund, Brunel University of London (to CB), Kay Kendall Leukemia Fund (KKL443) (to CB), 250 Great Minds Fellowship, University of Leeds (to SP), AMMF Cholangiocarcinoma Charity (to SP and PMC), and Bloodwise (17014) (to SP and CB)

Physical virology

Viruses are nanosized, genome-filled protein containers with remarkable thermodynamic and mechanical properties. They form by spontaneous self-assembly inside the crowded, heterogeneous cytoplasm of infected cells. Self-assembly of viruses seems to obey the principles of thermodynamically reversible self-assembly but assembled shells ('capsids') strongly resist disassembly. Following assembly, some viral shells pass through a sequence of coordinated maturation steps that progressively strengthen the capsid. Nanoindentation measurements by atomic force microscopy enable tests of the strength of individual viral capsids. They show that concepts borrowed from macroscopic materials science are surprisingly relevant to viral shells. For example, viral shells exhibit 'materials fatigue- and the theory of thin-shell elasticity can account - in part - for atomic-force-microscopy-measured force-deformation curves. Viral shells have effective Young's moduli ranging from that of polyethylene to that of plexiglas. Some of them can withstand internal osmotic pressures that are tens of atmospheres. Comparisons with thin-shell theory also shed light on nonlinear irreversible processes such as plastic deformation and failure. Finally, atomic force microscopy experiments can quantify the mechanical effects of genome encapsidation and capsid protein mutations on viral shells, providing virological insight and suggesting new biotechnological applications. © 2010 Macmillan Publishers Limited. All rights reserved

Dissociation between force and maximal Na+, K+-ATPase activity in rat fast-twitch skeletal muscle with fatiguing in vitro stimulation

This study investigated whether high frequency in vitro stimulation of rat fast-twitch extensor digitorum longus muscle depresses Na+, K+-ATPase (NKA) activity as measured by the maximal in vitro 3-O-MFPase assay. EDL muscles subjected to 10 s continuous 100 Hz stimulation reduced tetanic force by 51.8 +/- 5.1% which recovered to 81.2 +/- 6.1% after 1 min and remained stable over 1 h recovery period. A second bout reduced force by 50.3 +/- 3.8% of initial but had no eVect on 3-O-MFPase activity. Three minutes of intermittent stimulation (1 s at 100 Hz and 4 s recovery) resulted in 87.0 +/- 2.8% decline force with slow recovery (62.7 +/- 5.8% of initial after 1 h). The second 3-min bout reduced force by 83.3 +/- 3.6% of initial with no change in maximal 3-O-MFPase activity. These Wndings contrast previous human studies where fatiguing voluntary exercise depresses maximal NKA activity. This suggests that NKA in rat fast-twitch muscle is resistant to fatigue-induced inactivation under these conditions tions. Furthermore, the loss of force with fatigue was not related to depressed maximal NKA activity