D. Altavilla et al., INHIBITION OF TUMOR-NECROSIS-FACTOR AND REVERSAL OF ENDOTOXIN-INDUCEDSHOCK BY U-83836E, A 2ND-GENERATION LAZAROID IN RATS, British Journal of Pharmacology, 124(6), 1998, pp. 1293-1299
1 Antioxidants can exert protective effects in endotoxic shock by eith
er a reduction of the oxidant damage or attenuation of Tumour Necrosis
Factor (TNF-alpha) production. 2 Lazaroids are a family of compounds
that inhibit lipid peroxidation. Besides, they can also reduce TNF-alp
ha. U-83836E is a new lazaroid lacking the glucocorticoid ring. 3 Aim
of our study was to investigate the effect of U-83836E on TNF-alpha pr
oduction either in vivo or in vitro. Endotoxic shock was produced in m
ale rats by a single intravenous (i.v.) injection of 20 mg kg(-1) of S
. enteritidis lipopolysaccharide (LPS). LPS administration reduced sur
vival rate (0% survival, 72 h after endotoxin administration), decreas
ed mean arterial blood pressure, increased serum and macrophage TNF-a
and enhanced plasma malonylaldehyde (MAL) levels. Furthermore aortic r
ings from shocked rats showed a marked hyporeactivity to phenylephrine
(PE 1 nM-10 mu M). 4 Treatment with U-83836E (7.5, 15 and 30 mg kg(-1
), i.v.) 5 min after endotoxin challenge significantly protected again
st LPS induced lethality (90% survival rate and 80% survival rate 24 h
and 72 h after LPS injection respectively, following the highest dose
of the drug), reduced hypotension, blunted plasma MAL, decreased seru
m and macrophage TNF-alpha and restored the hyporeactivity of aortic r
ings to control values. In vitro LPS stimulation (50 mu g ml(-1) for 4
h) significantly increased cytokine production in macrophages (M Phi)
harvested from untreated normal rats. Pretreatment with pertussis tox
in (PT; 0.1, 1 and 10 ng ml(-1) 4 h before LPS) significantly increase
d TNF-alpha production. PT effects on these LPS responses were correla
ted with a PT mediated ADP ribosylation of a 41 kDa protein. U-83836E
(50 mu M) reduced, in a dose dependent manner, LPS induced TNF-alpha p
roduction and inhibited the PT effects on cytokine production and on A
DP ribosylation of the protein. 5 Our data suggest that lazaroids may
affect the early events associated with LPS receptor mediated activati
on of a G protein in LPS induced TNF-alpha production. These molecular
events may explain, at least in part, the in vivo inhibition of cytok
ine production and reversal of endotoxic shock.