Shiga toxin-1 regulation of cytokine production by human glomerular epithelial cells.
OBJECTIVE
Inflammatory cytokines may enhance renal injury in post-diarrheal hemolytic uremic syndrome (Stx HUS) by enhancing the cytotoxic effect of Shiga toxins (Stx). The sources of inflammatory cytokines in Stx HUS are unclear. Since Stx-1 potently inhibits protein synthesis by glomerular epithelial cells (GEC) and increases cytokine release by renal epithelial cells, we examined Stx-1 regulation of cytokine production by human GEC.


METHODS
Stx-1 (and cycloheximide (CHX), another protein synthesis inhibitor) cytotoxicity, protein synthesis inhibition, and effect on interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF) release and mRNA levels were determined.


RESULTS
Stx-1 alone had a modest stimulatory effect on inflammatory cytokine production by GEC that occurred at toxin concentrations ranging from minimal to 50% inhibition of protein synthesis. CHX, at concentrations that produced similar inhibition of protein synthesis, increased IL-1, IL-6, and TNF protein release and mRNA accumulation, but in a different time- and dose-dependent pattern than Stx. Lipopolysaccharide (LPS) did not change IL-1, but stimulated IL-6 and TNF production. LPS and Stx-1 combined stimulated production of all three cytokines to a greater extent than either toxin alone.


CONCLUSIONS
These data indicate that: (1) Stx-1 alone modestly stimulates GEC inflammatory cytokine production; (2) LPS and Stx-1 combined can potently enhance GEC cytokine release, and (3) this action of Stx-1 may relate in part to inhibition of protein synthesis but cannot be fully attributed to this effect.
Hughes
A K
AK
University of Utah School of Medicine and Salt Lake Veterans Affairs Medical Center, Salt Lake City, Utah 84132, USA.
Stricklett
P K
PK
Kohan
D E
DE
D000293:Adolescent; D000328:Adult; D000368:Aged; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D003513:Cycloheximide / Q000494:pharmacology; D016207:Cytokines / Q000235:genetics* / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects / Q000276:immunology; D006801:Humans; D007223:Infant; D007375:Interleukin-1 / Q000235:genetics / Q000378:metabolism; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D007678:Kidney Glomerulus / Q000166:cytology* / Q000276:immunology; D008875:Middle Aged; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D022622:Shiga Toxin 1 / Q000633:toxicity*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
D016207:Cytokines; D007375:Interleukin-1; D015850:Interleukin-6; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D022622:Shiga Toxin 1; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide