Free fatty acid palmitate impairs the vitality and function of cultured human bladder smooth muscle cells.
BACKGROUND
Incidence of urinary tract infections is elevated in patients with diabetes mellitus. Those patients show increased levels of the saturated free fatty acid palmitate. As recently shown metabolic alterations induced by palmitate include production and secretion of the pro-inflammatory cytokine interleukine-6 (IL-6) in cultured human bladder smooth muscle cells (hBSMC). Here we studied the influence of palmitate on vital cell properties, for example, regulation of cell proliferation, mitochondrial enzyme activity and antioxidant capacity in hBSMC, and analyzed the involvement of major cytokine signaling pathways.


RESULTS
HBSMC cultures were set up from bladder tissue of patients undergoing cystectomy and stimulated with palmitate. We analyzed cell proliferation, mitochondrial enzyme activity, and antioxidant capacity by ELISA and confocal immunofluorescence. In signal transduction inhibition experiments we evaluated the involvement of NF-κB, JAK/STAT, MEK1, PI3K, and JNK in major cytokine signaling pathway regulation. We found: (i) palmitate decreased cell proliferation, increased mitochondrial enzyme activity and antioxidant capacity; (ii) direct inhibition of cytokine receptor by AG490 even more strongly suppressed cell proliferation in palmitate-stimulated cells, while counteracting palmitate-induced increase of antioxidant capacity; (iii) in contrast knockdown of the STAT3 inhibitor SOCS3 increased cell proliferation and antioxidant capacity; (iv) further downstream JAK/STAT3 signaling cascade the inhibition of PI3K or JNK enhanced palmitate induced suppression of cell proliferation; (v) increase of mitochondrial enzyme activity by palmitate was enhanced by inhibition of PI3K but counteracted by inhibition of MEK1.


CONCLUSIONS
Saturated free fatty acids (e.g., palmitate) cause massive alterations in vital cell functions of cultured hBSMC involving distinct major cytokine signaling pathways. Thereby, certain cytokines might counteract the palmitate-induced downregulation of cell proliferation and vitality. This could be an important link to clinical findings of increased risk of metabolic related bladder diseases such as overactive bladder (OAB) and bladder pain syndrome/interstitial cystitis (BPS/IC).
Department of Pediatric Surgery, University Hospital of Leipzig, Leipzig, Germany.
Andreas
A
Oberbach
Nadine
N
Schlichting
Marco
M
Heinrich
Holger
H
Till
Jens-Uwe
JU
Stolzenburg
Jochen
J
Neuhaus
D000975:Antioxidants / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D015850:Interleukin-6 / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D010168:Palmitates / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D050791:STAT Transcription Factors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism; D001743:Urinary Bladder / Q000166:cytology*
D000975:Antioxidants; D015850:Interleukin-6; D016328:NF-kappa B; D010168:Palmitates; D012333:RNA, Messenger; C106644:SOCS3 protein, human; D050791:STAT Transcription Factors; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins