Markers of inflammation, proteolysis, and apoptosis in ESRD.
BACKGROUND
Hemodialysis (HD) is associated with protein catabolism and augmented apoptosis. Although the effect of metabolic acidosis and inflammatory cytokines on activation of the ubiquitin-proteasome pathway and branched-chain keto acid dehydrogenase (BCKAD) is well known, the effect of HD on these pathways remains unexplored.


METHODS
Twelve patients with end-stage renal disease were studied before and during HD. Eight controls also were studied. Plasma levels of complement components and cytokines, interleukin-1 (IL-1), IL-6, and tumor necrosis factor-alpha (TNF-alpha) were measured. Messenger RNA (mRNA) levels of caspase-3, a mediator of apoptosis; ubiquitin, a marker of proteolysis; and BCKAD-E2, an enzyme regulating branched-chain amino acid oxidation, were estimated in skeletal muscle biopsy specimens by means of reverse-transcriptase polymerase chain reaction. Annexin-V expression was quantified by DNA array. Before the study, participants were placed on a 1.2-g/kg/d protein diet, and metabolic acidosis was corrected.


RESULTS
During HD, plasma IL-6 levels increased from 7.54 +/- 2.24 to 27.86 +/- 4.94 pg/dL (P < 0.001). Complement component, IL-1, and TNF-alpha levels did not change significantly during HD. mRNA levels of caspase-3 (0.50 +/- 0.01 versus 0.81 +/- 0.04), annexin-V (0.94 +/- 0.06 versus 1.48 +/- 0.05; P < 0.001), ubiquitin (1.10 +/- 0.03 versus 1.44 +/- 0.03), and BCKAD-E2 (0.47 +/- 0.01 versus 0.81 +/- 0.04) increased in muscle during HD compared with pre-HD values (P < 0.001). mRNA levels of ubiquitin (0.62 +/- 0.03) and BCKAD-E2 (0.58 +/- 0.02) were greater in controls than pre-HD values (P < 0.05). There were significant positive correlations between plasma IL-6 levels and expression of caspase-3, ubiquitin, and BCKAD-E2 genes.


CONCLUSIONS
HD causes activation of cytokines, which may mediate the increase in gene expression of caspase-3, ubiquitin, and BCKAD-E2 in skeletal muscles.
Raj
Dominic S C
DS
Division of Nephrology University of New Mexico, Albuquerque, NM, USA. DRaj@salud.unm.edu
Shah
Hemangini
H
Shah
Vallabh O
VO
Ferrando
Arny
A
Bankhurst
Arthur
A
Wolfe
Robert
R
Zager
Philip G
PG
D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide) / Q000096:biosynthesis / Q000235:genetics; D000138:Acidosis / Q000209:etiology / Q000378:metabolism; D000328:Adult; D017209:Apoptosis; D001706:Biopsy; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis / Q000235:genetics; D003131:Combined Modality Therapy; D003165:Complement System Proteins / Q000032:analysis; D016207:Cytokines / Q000097:blood; D018753:Diet, Protein-Restricted; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007249:Inflammation / Q000097:blood* / Q000150:complications; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000150:complications / Q000178:diet therapy / Q000628:therapy; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D011506:Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D006435:Renal Dialysis / Q000009:adverse effects; D025801:Ubiquitin / Q000096:biosynthesis / Q000235:genetics
D016207:Cytokines; D011506:Proteins; D012333:RNA, Messenger; D025801:Ubiquitin; D003165:Complement System Proteins; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases