Inactivating mutations in the von Hippel-Lindau (VHL) tumor suppressor gene are associated with clear cell renal cell carcinoma (VHL

The leucine metabolite ␤-hydroxy-␤-methylbutyrate (HMB) prevents muscle protein degradation in cancer-induced weight loss through attenuation of the ubiquitin-proteasome proteolytic pathway. To investigate the mechanism of this effect, the action of HMB on protein breakdown and intracellular signaling leading to increased proteasome expression by the tumor factor proteolysis-inducing factor (PIF) has been studied in vitro using murine myotubes as a surrogate model of skeletal muscle. A comparison has been made of the effects of HMB and those of eicosapentaenoic acid (EPA), a known inhibitor of PIF signaling. At a concentration of 50 mol/L, EPA and HMB completely attenuated PIF-induced protein degradation and induction of the ubiquitin-proteasome proteolytic pathway, as determined by the "chymotrypsin-like" enzyme activity, as well as protein expression of 20S proteasome ␣-and ␤-subunits and subunit p42 of the 19S regulator. The primary event in PIF-induced protein degradation is thought to be release of arachidonic acid from membrane phospholipids, and this process was attenuated by EPA, but not HMB, suggesting that HMB might act at another step in the PIF signaling pathway. EPA and HMB at a concentration of 50 mol/L attenuated PIF-induced activation of protein kinase C and the subsequent degradation of inhibitor B␣ and nuclear accumulation of nuclear factor B. EPA and HMB also attenuated phosphorylation of p42/44 mitogen-activated protein kinase by PIF, thought to be important in PIF-induced proteasome expression. These results suggest that HMB attenuates PIF-induced activation and increased gene expression of the ubiquitin-proteasome proteolytic pathway, reducing protein degradation.

Loss of skeletal muscle is a major factor in the poor survival of patients with cancer cachexia. This study examines the mechanism of catabolism of skeletal muscle by a tumour product, proteolysis-inducing factor (PIF). Intravenous administration of PIF to normal mice produced a rapid decrease in body weight (1.55 ± 0.12 g in 24 h) that was accompanied by increased mRNA levels for ubiquitin, the Mr 14 000 ubiquitin carrier-protein, E2, and the C9 proteasome subunit in gastrocnemius muscle. There was also increased protein levels of the 20S proteasome core and 19S regulatory subunit, detectable by immunoblotting, suggesting activation of the ATP-ubiquitin-dependent proteolytic pathway. An increased protein catabolism was also seen in C2C12 myoblasts within 24 h of PIF addition with a bell-shaped dose–response curve and a maximal effect at 2–4 nM. The enhanced protein degradation was attenuated by anti-PIF antibody and by the proteasome inhibitors MG115 and lactacystin. Glycerol gradient analysis of proteasomes from PIF-treated cells showed an elevation in chymotrypsin-like activity, while Western analysis showed a dose-related increase in expression of MSSI, an ATPase that is a regulatory subunit of the proteasome, with a dose–response curve similar to that for protein degradation. These results confirm that PIF acts directly to stimulate the proteasome pathway in muscle cells and may play a pivotal role in protein catabolism in cancer cachexia. © 2001 Cancer Research Campaign http://www.bjcancer.com

Recent cross‐sectional studies suggest an important role for transitional B lymphocytes (CD19 + CD24hiCD38hi) in promoting transplant tolerance, and protecting from late antibody‐mediated rejection (ABMR). However, prospective studies are lacking. This study enrolled 73 de novo transplant recipients, and collected serial clinical, immunological and biochemical information over 48 ± 6 months. Cell phenotyping was conducted immediately prior to transplantation, and then on five occasions during the first year posttransplantation. When modeled as a time‐dependent covariate, transitional B cell frequencies (but not total B cells or “regulatory” T cells) were associated with protection from acute rejection (any Banff grade; HR: 0.60; 95% CI: 0.37–0.95; p = 0.03). No association between transitional B cell proportions and either de novo donor‐specific or nondonor‐specific antibody (dnDSA; dnNDSA) formation was evident, although preserved transitional B cell proportions were associated with reduced rejection rates in those patients developing dnDSA. Three episodes of ABMR occurred, all in the context of nonadherence, and all associated with in vitro anti‐HLA T cell responses in an ELISPOT assay (p = 0.008 versus antibody‐positive patients not experiencing ABMR). This prospective study supports the potential relevance of transitional (“regulatory”) B cells as a biomarker and therapeutic intervention in transplantation, and highlights relationships between humoral immunity, cellular immunity and nonadherence.

Atrophy of skeletal muscle reduces both the quality and quantity of life of patients with cancer cachexia. Loss of muscle mass is thought to arise from a reduction in protein synthesis combined with an enhanced rate of protein degradation, and few treatments are available to counteract this process. Eicosapentaenoic acid (EPA) has been shown to attenuate the enhanced protein degradation, but to have no effect on protein synthesis. This study examines the effect of EPA combined with a protein and amino-acid supplementation on protein synthesis and degradation in gastrocnemius muscle of mice bearing the cachexia-inducing MAC16 tumour. Muscles from cachectic mice showed an 80% reduction in protein synthesis and about a 50-fold increase in protein degradation compared with muscles from nontumour-bearing mice of the same age and weight. Treatment with EPA (1 g kg−1) daily reduced protein degradation by 88%, but had no effect on protein synthesis. Combination of EPA with casein (5.35 g kg−1) also had no effect on protein synthesis, but when combined with the amino acids leucine, arginine and methionine there was almost a doubling of protein synthesis. The addition of carbohydrate (10.7 g kg−1) to stimulate insulin release had no additional effect. The combination involving the amino acids produced almost a doubling of the ratio of protein synthesis to protein degradation in gastrocnemius muscle over that of EPA alone. No treatment had a significant effect on tumour growth rate, but the inclusion of amino acids had a more significant effect on weight loss induced by the MAC16 tumour than that of EPA alone. The results suggest that combination therapy of cancer cachexia involving both inhibition of the enhanced protein degradation and stimulation of the reduced protein synthesis may be more effective than either treatment alone.

Comparing glycaemic benefits of active versus passive lifestyle intervention in kidney allograft recipients (CAVIAR): a randomised controlled trial', Transplantation.

The pattern of the coronary arteries of the domestic fowl is described. In the fowl heart the longitudinal sulci do not contain descending rami of the coronary arteries. The largest coronary vessels are the right and left deep coronary arteries, which early in their course come to lie on the ventral face of the I-V septum immediately below the endocardium. The circumflex arteries which occupy the corresponding coronary sulci are minor trunks. Differences in the relative distribution of the right and left deep coronary arteries allow recognition of three heart types: Heart Type Two, i.e., right coronary artery dominance, is found to be the commonest; Heart Type Three (left coronary artery dominance), and Heart Type One (balanced coronary circulation) are less common. Some details of the origin and course of the atrial, infundibular, conal and valvular arteries are given. The presence of homo-coronary and intercoronary anastomoses is noted.The coronary vessels of the domestic fowl receive little attention in the standard text book. Kaupp ('18) gives a brief, rather confusing description of the coronary arteries; Sturkie ('54) locates the right coronary artery on the ventral surface of the heart and the left coronary on the dorsal surface, and indicates that the terminal branches of these vessels anastomose freely; Simons ('60) describes the coronary arteries as coursing over the surface of the heart. Petren ('26) examined 139 hearts of different species of birds, including 64 fowl hearts; Myczkowski ('60) examined 67 hearts of several avian species and included 14 fowls in his survey. The latter two authors have described the ventricular arteries in some detail, but disagree as to whether the superficial or deep rami constitute the larger trunks. The atrial vessels seem to have received less attention.Terminal anastomoses between right and left circumflex vessels have been mentioned by Petren ('26).The histogenesis of the coronary arteries of the chick is described by Hughes ('42, '43).The present study was undertaken in collaboration with colleagues using the domestic fowl in an investigation of atheromatous conditions of the coronary vessels. TOPOGRAPHICAL OBSERVATIONSA general examination of the heart surf ace confirms that the circumflex coronary sulcus resembles that of the mammal and contains vessels surrounded by fat in the sub-epicardial connective tissue.The longitudinal sulci, unlike those of the mammal, are not channels containing the descending rami of the coronary arteries, but shallow furrows marking the junction of septal and outer ventricular walls. Owing to the orientation of the heart in situ, the left or ventral longitudinal sulcus courses obliquely on the ventral or anterior surface of the heart, crosses this surface above the apex, and becomes continuous with the right or dorsal longitudinal sulcus. The latter connects to the circumflex sulcus at a wide shallow depression which contains the termination of a large vena cordis media. The incisura apicis cordis does not necessarily corres...

Proteolysis-inducing factor (PIF) is a sulphated glycoprotein produced by cachexia-inducing tumours, which initiates muscle protein degradation through an increased expression of the ubiquitin -proteasome proteolytic pathway. The role of kinase C (PKC) in PIFinduced proteasome expression has been studied in murine myotubes as a surrogate model of skeletal muscle. Proteasome expression induced by PIF was attenuated by 4a-phorbol 12-myristate 13-acetate (100 nM) and by the PKC inhibitors Ro31-8220 (10 mM), staurosporine (300 nM), calphostin C (300 nM) and Gö 6976 (200 mM). Proteolysis-inducing factor-induced activation of PKC a , with translocation from the cytosol to the membrane at the same concentration as that inducing proteasome expression, and this effect was attenuated by calphostin C. Myotubes transfected with a constitutively active PKC a (pCO 2 ) showed increased expression of proteasome activity, and a longer time course, compared with their wild-type counterparts. In contrast, myotubes transfected with a dominant-negative PKC a (pKS1), which showed no activation of PKC a in response to PIF, exhibited no increase in proteasome activity at any time point. Proteolysis-inducing factor-induced proteasome expression has been suggested to involve the transcription factor nuclear factor-kB (NF-kB), which may be activated through PKC. Proteolysis-inducing factor induced a decrease in cytosolic I-kBa and an increase in nuclear binding of NF-kB in pCO 2 , but not in pKS1, and the effect in wild-type cells was attenuated by calphostin C, confirming that it was mediated through PKC. This suggests that PKC may be involved in the phosphorylation and degradation of I-kBa, induced by PIF, necessary for the release of NF-kB from its inactive cytosolic complex.