Chemically modified tetracycline (CMT)-3 inhibits histamine release and cytokine production in mast cells: possible involvement of protein kinase C.
OBJECTIVE
To find novel inhibitors of mast cell function we have studied the effect of a potent, non-antimicrobial, chemically modified tetracycline, CMT-3 or COL-3, on key functions of mast cells.


RESULTS
In the presence of 25 microM CMT-3, the 48/80-induced histamine release from rat serosal mast cells was inhibited significantly, to 43.0 +/- 7.3% of control. Similarly, the activation-induced secretion of TNF-alpha and IL-8 by HMC-1 cells were decreased in the presence of 25 microM CMT-3 to 13.5 +/- 4.1% and 9.7 +/- 1.1% of control, respectively. CMT-3 did not cause intracellular accumulation of TNF-alpha but instead it reduced the expression of TNF-alpha mRNA in HMC-1 cells. Moreover, CMT-3 was found to significantly inhibit the protein kinase C (PKC) activity with IC(50) value of 31 microM. CMT-3 inhibited effectively both human recombinant PKCalpha and PKCdelta isoforms. In comparison to doxycycline, CMT-3 was more effective as an inhibitor of both cytokine production and PKC activity.


CONCLUSIONS
Considering the central role of PKC in mast cell activation, PKC inhibition could, at least partially, explain the observed inhibitory effects of CMT-3. The inhibition of the key proinflammatory functions of mast cells by CMT-3 suggests its potential clinical usefulness in the treatment of allergic and inflammatory disorders.
Sandler
C
C
Institute of Biomedicine, Department of Pharmacology, Helsinki University, Helsinki, Finland.
Ekokoski
E
E
Lindstedt
K A
KA
Vainio
P J
PJ
Finel
M
M
Sorsa
T
T
Kovanen
P T
PT
Golub
L M
LM
Eklund
K K
KK
D000818:Animals; D018952:Antigens, CD34 / Q000096:biosynthesis; D001921:Brain / Q000378:metabolism; D002273:Carcinogens; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003001:Cloning, Molecular; D016207:Cytokines / Q000096:biosynthesis* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005312:Fetal Blood; D006632:Histamine / Q000378:metabolism*; D006636:Histamine Release; D006801:Humans; D007249:Inflammation; D016209:Interleukin-8 / Q000378:metabolism; D008297:Male; D008407:Mast Cells / Q000166:cytology / Q000378:metabolism*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013754:Tetracyclines / Q000494:pharmacology*; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D018952:Antigens, CD34; D002273:Carcinogens; D016207:Cytokines; D016209:Interleukin-8; D012333:RNA, Messenger; D013754:Tetracyclines; D014409:Tumor Necrosis Factor-alpha; C117155:tetracycline CMT-3; D015240:Phorbol 12,13-Dibutyrate; D006632:Histamine; C497260:Prkcd protein, rat; C496628:PRKCA protein, human; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta