Michael H. Brooke

Neurotrophic factors decrease the release of creatine kinase and prostaglandin E2 from metabolically stressed muscle

We have used an in vitro model of oxidative stress by exposing rat muscle to 2:4 dinitrophenol. This causes an efflux of creatine kinase (CK) and prostaglandin E2 (PGE2) commonly used as indicators of muscle cell damage. We then investigated compounds with a putative cell protective effect in the system. Ciliary neurotrophic factor, brain derived neurotrophic factor and insulin like growth factor 1 all prevent the release of PGE2 and CK. To the extent that these indicators may reflect cell damage, the results might support the investigation of the therapeutic potential of these compounds in muscle disease.

Effects of calcium channel antagonists on the release of prostaglandin e2 from metabolically stressed muscle

Calcium influx plays a critical role in the activation of the arachidonic cascade in muscle damage. We examined the effects of L-type calcium channel antagonists on the release of prostaglandin E2 (PGE2), a bioactive metabolite of arachidonic acid metabolism, from skeletal muscle. The basal release of PGE2 was not affected by calcium channel inhibitors, such as nifedipine and verapamil. The release of PGE2 induced by dinitrophenol, an uncoupler of oxidative phosphorylation, was abolished by nifedipine and verapamil at 50 and 150 microM, respectively. It was not necessary to include the calcium channel blockers in the medium before or at the time of dinitrophenol stimulation to produce the effect on PGE2 release. The release of PGE2 was prevented for as long as calcium channel blockers were present in the medium after the dinitrophenol stress.

Mild Hypothermia Preserves Contractile Function and Inhibits Prostaglandin E2 Release from Metabolically Stressed Skeletal Muscle

An in vitro model of muscle damage was used to investigate the protective effect of mild hypothermia in muscle injury. Rat epitrochlearis muscles were dissected in their entirety and suspended in Krebs-Ringer solution and DNP, a mitochondrial uncoupler, was added. PGE2 and lactate release and the contractile response to stimulation were measured and compared to untreated controls. Experiments were done at 37, 35, 33 and 27 degrees C. At 37 degrees C, DNP stimulated muscle releases large amounts of PGE2 and lactate and is unable to contract. As the temperature is reduced, there is progressive preservation of contractile force, although high lactate levels at the lowest temperatures indicate that the metabolic stress is still present. In contrast, DNP stimulated PGE2 release is completely inhibited at or below 35 degrees C and may be related to a similar protective phenomenon seen in experimental ischemic neuronal death.

Issues in Myoblast Transfer

The work which forms the basis for my comments was done by the clinical evaluators in the CIDD group (1). I shall present only the conclusions, not the studies themselves.