THE INFLUENCE OF BRAIN SEROTONERGIC SYSTEM ON THE EXPRESSION AND ACTIVITY OF
CYTOCHROME P450 IN THE LIVER
Marta Rysz, Ewa Bromek, Anna Haduch, Władysława Anna Daniel Institute of Pharmacology, Polish Academy of Sciences, Smętna 12, PL 31-343 Kraków, Poland
1. INTRODUCTION
Studies conducted so far have indicated that hormones acting as ligands of cytoplasmic and nuclear receptors (growth hormone, glucocorticosteroids, thyroid hormones) influence transcriptional level of genes encoding cytochrome P450 (CYP) isoenzymes [1-3]. All the above-mentioned hormones are controlled by the hipothalamo-pituitary axis. It is also known that the hypothalamus is den-sely innervated by serotonergic axons projecting from raphe nuclei (dorsal nuclei B6, B7 and median nuclei B5, B8). Serotonergic neurons reach hypothalamic nuclei forming parvocellular neurosecretory system (the paraventricular and arcuate nuclei), Thus, it can be assumed that brain serotonergic projections to the hypothalamus influence hepatic cytochrome P450 expression via the above-mentioned hormones. The aim of our study was to investigate the effect of damage to the serotonergic system on the expression of liver cytochrome P450 and serum level of the key hormones (growth hormone, thyroid hormones and corticosterone) that contribute to this process.
2. MATERIALS AND METHODS
The experiments were carried out on male Wistar rats. The 5,7-DHT (5,7-
dihydroxytryptamine), a selective serotonergic neurotoxin was injected into dor-
sal and median raphe nuclei (in a dose of 10 μg/raphe nucleus) or intracere-
broventricularly (in a dose of 70μg/ventricle). Ten days after the neurotoxin in-
jection, brain structures, liver tissue and blood were collected and prepared for
further analysis. The levels of noradrenaline (NA), dopamine (DA) and serotonin
(5-HT) in the brain structures were determined by a high pressure liquid chro-
matography (HPLC) with an electrochemical detection.
The activity of individual cytochrome P450 isoenzymes was determined in mi-
crosomal fraction of the liver, based on the velocity of reactions specific for in-
dividual isoenzymes: caffeine 3-N-demethylation (catalyzed by CYP2C11 and
CYP1A) and caffeine 8-hydroxylation (catalyzed by CYP1A), testosterone hy-
droxylation at positions: 2, 6 (catalyzed by CYP3A); 2, 16 (catalyzed by
CYP2C11), 7 (catalyzed by CYP2A) and 16 (catalyzed by CYP2B); warfarin 7-
hydroxylation (catalyzed by CYP2C6) and bufuralol 1’-hydroxylation (catalyzed
by CYP2D). Specific metabolites formed in vitro were assayed using HPLC with
UV of fluorescence detection [4]. Serum concentrations of hormones and inter-
leukines were estimated using ELISA kits.
Fig. 1. The effect of injection of 5,7-DHT into the dorsal and median raphe nuclei or
intracerebroventricularly on the level of serotonin in rat brain structures
3. RESULTS %
of
co
ntr
ol
CYP1A
1/2
CYP2C
11
CYP3A
0
50
100
150
200
*
* *
Fig. 3. The effect of injection of 5,7-DHT into dorsal and median
raphe nuclei on the protein level of liver CYP isoenzymes
Fig. 4. The effect of injection of 5,7-DHT into dorsal and me-
dian raphe nuclei on the hormones and cytokines level
CYP1A CYP2A
CYP2B
CYP2C6
CYP2C11
CYP2D
CYP3A
5,7-DHT
GROWTH HOR-MONE
TST
CORT T4
T3 IL-2 IL-6
5,7-DHT
Enzyme activity Protein level
SUMMARY
ACKNOWLEDGMENTS
This work was financially supported by the project Interdisciplinary PhD Studies „Molecular Sciences for Medicine (co-financed by the Eu-
ropean Social Fund within the Human Capital Operational Programme) and by statutory funds from the Institute of Pharmacology, PAS
CONCLUSIONS
1. Either mode of lesion (intracerebroventricular or intrastructural) reduced the serotonin level in all the brain structures ex-amined. In the hypothalamus, the 5-HT level fell to 35% and 18% of the control value (after injection to the raphe nuclei and lateral ventricles, respectively).
2. In the liver, similar effects were observed after either mode of lesion: 5,7-DHT increased the activity of CYP1A, CYP3A and CYP2C11, while the activity of CYP2A, 2B, 2C6 and 2D remained unchanged.
3. The increased activity of CYP1A, 3A and 2C11 correlated positively with the enhanced enzyme protein levels.
4. Simultaneously, a significant rise in the serum concentration of the growth hormone, testosterone and corticosterone and drop of triiodothyronine, but no change in thyroxin and cytokine levels (IL-2 and IL-6) were observed.
5. The results obtained indicate that brain serotonergic system contributes to the regulation of liver cytochrome P450. Ho-wever, its effect on the main male isoforms (CYP2C11, CYP3A) is opposite to that observed for dopaminergic or noradre-nergic systems.
REFERENCES 1. Monostory K., Pascussi J.M., Kobori L., Dvorak Z., Hormonal regulation of CYP1A expression. Drug Metabolism Reviews, 2009, 41, 547-72. 2. Waxman D.J., Holloway M.G., Sex differences in the expression of hepatic drug metabolizing enzymes. Molecular Pharmacology, 2009, 76, 215-228 3. Wójcikowski J., Gołembiowska K., Daniel WA., The regulation of liver cytochrome P450 by the brain dopaminergic system. Curr Drug Metab., 2007,
8, 631-8. 4. Sadakierska-Chudy A., Haduch A., Rysz M., Gołembiowska K., Daniel WA; The role of brain noradrenergic system in the regulation of liver cyto-
chrome P450 expression, Biochemical Pharmacology, 2013, 86, 800-807
Fig. 2. The effect of injection of 5,7-DHT into dorsal and median raphe nuclei or
intracerebroventricularly on the activity of liver CYP isoenzymes
Ht—Hypothalamus;
Hp—Hippocampus;
BS—Brain Stem;
FCx—Frontal cortex;
St—Striatum;
Na—Nucleus accum-
bens;
Th—Thalamus;
Mo—Medulla oblongata
Cb—Cerebellum;
Rcx– Rest of cortex
co
ncen
trati
on
(p
g/m
g o
f ti
ssu
e)
0
200
400
600
800
***
***
*
***
*
*
*
*
***
*
*
SHAM control
5,7-DHT
Naive
SEROTONIN - after i.raphe injection of 5,7-DHT
Ht Hp BS FCx St Na Th Mo Cb Rcx Ht Hp BS FCx St Na Th Mo Cb Rcx
co
ncen
trati
on
(p
g/m
g o
f ti
ssu
e)
0
200
400
600
800
1000
Naive
Sham control
5,7-DHT
SEROTONIN - after icv. injection of 5,7-DHT
***
***
***
*** *** ******
***
***
% o
f co
ntr
ol
1A 1A
1A 1A
2A
2B
2C11
2C11 3A
3A 2C
62D
0
50
100
150
2001-N 3-N 7-N 8-OH
caffeine warfarin bufuralol
*
*
7 16 2 16 2 6
* *
testosterone
*
*
7-OH -OH
% o
f co
ntr
ol
1A 1A 1A 1A 2A 2B2C
11
2C11 3A 3A
0
50
100
150
200
250caffeine testosterone
**
*
* * *
1-N 3-N 7-N 8-OH 7 16 2 16 2 6
1) After i.raphe injection of 5,7-DHT 2) After icv. injection of 5,7-DHT
% o
f co
ntr
ol
GH TST CORT. T4 T3 IL-2 IL-60
50
100
150
1000
1500
2000
2500
3000
*
**
Hormones Cytokines
*
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