Recent Publications by CFE Educators

The 39-kDa receptor-associated protein (RAP) is a specialized chaperone for members of the low density lipoprotein receptor gene family, which also binds heparin. Previous studies have identified a triplicate repeat sequence within RAP that appears to exhibit differential functions. Here we generated a series of truncated and site-directed RAP mutants in order to define the sites within RAP that are important for interacting with heparin and low density lipoprotein receptor-related protein (LRP). We found that high affinity binding of RAP to heparin is mediated by the carboxyl-terminal repeat of RAP, whereas both the carboxyl-terminal repeat and a combination of amino and central repeats exhibit high affinity binding to LRP. Several motifs were found to mediate the binding of RAP to heparin, and each contained a cluster of basic amino acids; among them, an intact R(282)VSR(285)SR(287)EK(289) motif is required for high affinity binding of RAP to heparin, whereas two other motifs, R(203)LR(205)R(206) and R(314)ISR(317)AR(319), also contribute to this interaction. We also found that intact motifs of both R(203)LR(205)R(206) and R(282)VSR(285)SR(287)EK(289) are required for high affinity binding of RAP to LRP, with the third motif, R(314)ISR(317)AR(319), contributing little to RAP-LRP interaction. We conclude that electrostatic interactions likely contribute significantly in the binding of RAP to both heparin and LRP and that high affinity interaction with both heparin and LRP appears to require mostly overlapping sequence motifs within RAP.

Although the tachykinins substance P (SP) and neurokinin A (NKA) are coreleased from primary afferent nociceptors and act via neurokinin (NK) receptors, their differential effects in vivo are not known. Despite pharmacological evidence that NKA preferentially binds NK-2 receptors, this receptor is not found in spinal cord neurons. Thus, in the present studies, we compared the extent to which SP and NKA contribute to spinal nociceptive processing via the NK-1 receptor. We found that SP and NKA induce NK-1 receptor internalization with identical dose dependence and induce increases in intracellular calcium at the same concentrations, suggesting that SP and NKA equally activate the NK-1 receptor. We found, however, that the selective NK-1 receptor antagonist GR 205171 blocked NKA but not SP-induced NK-1 receptor internalization in the rat spinal cord in vivo and in embryonic day 19 rat spinal neurons in vitro. Using this selectivity of GR 205171 for NKA-induced NK-1 receptor activation, we examined the relative contribution of SP and NKA to noxious stimulus-induced activation of spinal NK-1 receptors. We estimate that NKA contributes to at least 50% of the NK-1 receptor activation in lamina I. Under inflammatory conditions, all noxious stimulus-induced NK-1 receptor internalization in deep dorsal horn neurons was blocked by GR 205171, suggesting that it is entirely NKA-mediated. Substance P-mediated NK-1 receptor internalization was focused at the site of termination of stimulated nociceptors but NKA also activated NK-1 receptors at more distant sites. We conclude that NKA not only targets the NK-1 receptor but may be a predominant pronociceptive primary afferent neurotransmitter.

There is evidence that noradrenaline contributes to the development and maintenance of neuropathic pain produced by trauma to a peripheral nerve. It is, however, unclear which subtype(s) of alpha adrenergic receptors (AR) may be involved. In addition to pro-nociceptive actions of AR stimulation, alpha(2) AR agonists produce antinociceptive effects. Here we studied the contribution of the alpha(2) AR subtypes, alpha(2A), alpha(2B) and alpha(2C) to the development of neuropathic pain. We also examined the antinociceptive effect produced by the alpha(2) AR agonist dexmedetomidine in nerve-injured mice. The studies were performed in mice that carry either a point (alpha(2A)) or a null (alpha(2B) and alpha(2C)) mutation in the gene encoding the alpha(2) AR. To induce a neuropathic pain condition, we partially ligated the sciatic nerve and measured changes in thermal and mechanical sensitivity. Baseline mechanical and thermal withdrawal thresholds were similar in all mutant and wild-type mice; and, after peripheral nerve injury, all mice developed comparable hypersensitivity (allodynia) to thermal and mechanical stimulation. Dexmedetomidine reversed the allodynia at a low dose (3 microg kg(-1), s.c.) and produced antinociceptive effects at higher doses (10 - 30 microg kg(-1)) in all groups except in alpha(2A) AR mutant mice. The effect of dexmedetomidine was reversed by intrathecal, but not systemic, injection of the alpha(2) AR antagonist RS 42206. These results suggest that neither alpha(2A), alpha(2B) nor alpha(2C) AR is required for the development of neuropathic pain after peripheral nerve injury, however, the spinal alpha(2A) AR is essential for the antinociceptive effects of dexmedetomidine.

The clinician evaluating a woman with symptoms potentially indicative of coronary heart disease faces the challenge of choosing the appropriate diagnostic test. The use of noninvasive testing in women has been controversial due to a perception of diminished accuracy, limited female representation, and technical limitations that compromise efficacy. Recent meta-analyses and large observational series report marked improvements in accuracy for women undergoing exercise treadmill, echocardiography, and nuclear testing. Electron beam computed tomography is a relatively new technique, and the body of evidence is still developing. An adequate body of evidence supports the use of noninvasive testing for intermediate risk, symptomatic women and may result in improved diagnostic and therapeutic decision making.