PARASITE BIOLOGY AND BIOCHEMISTRY
o f a single altered b e h a v i o u r , a r e p l e i o t r o p i c a n d therefore d e f e c t i v e in o t h e r c h e m i c a l sensitivities.
4. T h e D y f p h e n o t y p e is a s s o c i a t e d with t h e l o s s o f sensiti
vity t o m a n y different c h e m i c a l s . Alterations in t h e s h a p e o r matrix c o n t e n t o f t h e amphidial c h a n n e l a l s o result in a D y f p h e n o t y p e .
5. W h i l e w a t e r s o l u b l e c h e m i c a l s s e e m t o h a v e r e c e p t o r s o n the n e u r o n s w h o s e cilia a r e e x p o s e d t o t h e o u t s i d e (ASH a n d A D D , attraction t o a n d repulsion b y volatile c h e m i c a l s are m e d i a t e d b y r e c e p t o r s p r e s e n t o n t h e amphidial wing cells AWA, AWES a n d A W C .
R E F E R E N C E S
BARGMANN C . I . , THOMAS J . H . and HORVITZ H . R . : Chcmosensory cell function in the behavior and development of Caenorbabditis ele
gans. Cold Spring Harbor Symp. Quant. Biol.. 1990, LV, 529-538.
BARGMANN C . I . , HARTWEIG E. and HORVITZ H . R . : Odorant-selective genes and neurons mediate olfaction in C. elegans. Cell, 1993,
74, 515-527.
CHALFIE M. and WHITE J.-G. : The nervous system in The Nematode Caenorbabditis elegans. Wood W . B . (ed.), Cold Spring Harbor Lab. C . S . H . , New York, 1988, 337-391.
WHITE J . G . , SOUTHGATE E., THOMSON J . N . and BRENNER S. : The struc
ture of the nervous system o f the nematode Caenorbabditis ele
gans. Philos. Trans. R. Soc. London, Ser. B., 1986, 314, 1-340.
N - A C E T Y L A T I O N O F P O L Y A M I N E S A N D BIOGENIC A M I N E S I N PARASITIC N E M A T O D E S
AISIEN S.O.*, DAVIDS G**, HELLMUND C**, NIEMANN G.**
AND WALTER R.D.**
KEYWORDS Polyamines. biogenic amines. N-acetylase. nematodes.
T
h e p r e v i o u s l y d e s c r i b e d p o l y a m i n e N - a c e t y l a s e from Fasciola bepatica h a s b e e n o b s e r v e d to have an additional function, t h e acetylation o f b i o g e n i c a m i n e s (Aisien a n d W a l t e r , 1 9 9 2 , 1 9 9 3 ) . It w a s c o n c l u d e d that N - a c e t y l a t i o n plays a major role in t h e a m i n e m e t a b o l i s m o f trematodes. In continuation o f t h e s e o n g o i n g studies o n t h e p r o c e s s o f N- acetylation in parasitic helminths, w e h a v e d e t e c t e d b i o g e n i c a m i n e acetylation in t h e tissue dwelling filaria Onchocerca volvulus a n d t h e intestinal parasite Ascaris suum. T h e aim o f o u r study w a s t o a s c e r t a i n if o u r p r e v i o u s finding that a single e n z y m e is r e s p o n s i b l e for d i a m i n e , p o l y a m i n e a n d b i o g e n i c a m i n e acetylation in trematodes, is a feature c o m m o n to all h e l m i n t h s . Results from investigation using A.
suum indicate that t w o i n d e p e n d e n t e n z y m e s are respecti
vely r e s p o n s i b l e for p o l y a m i n e a n d b i o g e n i c a m i n e acetyla
t i o n . C h r o m a t o g r a p h y o f t h e 1 0 0 , 0 0 0 g s u p e r n a n t o n DEAE-cellulose r e v e a l e d t w o e n z y m e activity p e a k s , b o t h o f w h i c h have activity for histamine. T h e first p e a k w a s o b s e r v e d to c a t a l y s e o n l y b i o g e n i c a m i n e acetylation w h i l e t h e s e c o n d a c e t y l a t e d p u t r e s c i n e a n d o t h e r d i a m i n e s . O n t h e basis o f the Km- v a l u e s o b t a i n e d with b o t h e n z y m e s for hista
m i n e , p e a k II s e e m s t o b e m o r e specific for this substrate
* Department of Zoology, University of Benin, Benin-City, Nigeria.
** D e p a r t m e n t o f B i o c h e m i c a l Parasitology, Bernhard-Nocht Institute for Tropical Medicine, 20359 Hamburg, Germany.
with a Km- v a l u e o f 3 7 uM c o m p a r e d to p e a k I w h i c h h a d a Km- v a l u e o f 500LIM. In contrast t h e Km- v a l u e s o b t a i n e d for b i o g e n i c a m i n e s with p e a k I w e r e as follows : T y r a m i n e , 0 . 9 uM, tryptamine, 1.7 uM, o c t o p a m i n e , 2 9 uM, serotonin, 9 . 5 uM a n d ß-phenylethylamine, 1.5 uM. Epinephrine, n o r e p i n e phrine a n d d o p a m i n e w e r e n o t physiological substrates for t h e N - a c e t y l a s e . T h e e n z y m e h a s a m o l e c u l a r m a s s o f a p p r o x i m a t e l y 3 0 k D a a n d w a s slightly inhibited b y c o e n z y m e A, a product o f t h e acetylation p r o c e s s . T h e specificity o f p e a k II for diamines a n d histamine a n d its lack o f activity for p o l y a m i n e s indicates that this e n z y m e is most probably the novel putrescine acetylase previously reported b y Wittich and Walter ( 1 9 9 0 , 1 9 9 1 ) from O. volvulus a n d A. suum.
A S S E S S M E N T O F THE POLYAMINE M E T A B O L I S M O F FILARIAL W O R M S A S A T A R GET F O R C H E M O T H E R A P Y
MÜLLER S.*, H U N T E R K.J.**, K O N D U R S*, HELLMUND C.*, FAIRLAMB A.H.** & WALTER R.D.*
KEYWORDS : Polyamines. metabolism, chemotherapy, filaria. N-acetyltransfe- rase. polyamine oxidase. S-adenosylmethionine decarboxylase.
Polyamines a r e essential for t h e proliferation a n d diffe
rentiation o f c e l l s a n d o r g a n i s m s . T h e p r e s e n c e o f poly
a m i n e s h a s b e e n d e m o n s t r a t e d in Onchocerca volvulus a n d a l l i e d p a r a s i t e s a n d t h e i n v e s t i g a t i o n o f t h e p o l y a m i n e m e t a b o l i s m h a s i d e n t i f i e d u n u s u a l p a t h w a y s w h i c h a r e p o t e n t i a l c h e m o t h e r a p e u t i c t a r g e t s . T h e s e p a t h w a y s a r e crucial for parasite survival a n d differ in s o m e b i o c h e m i c a l a s p e c t s from t h e h o s t c o u n t e r p a r t s , thus a l l o w i n g for t h e rational d e s i g n o f drugs for a parasite-specific c h e m o t h e r a p e u t i c attack. A p r o p o s e d s c h e m e o f t h e p o l y a m i n e m e t a b o l i s m in filarial w o r m s is s h o w n in Figure 1.
S i n c e t h e p r e s e n c e o f o r n i t h i n e d e c a r b o x y l a s e ( O D C ) acti
vity is q u e s t i o n a b l e , t h e initial s t e p in t h e b i o s y n t h e s i s o f p o l y a m i n e s a p p e a r s t o b e l a c k i n g a n d t h u s t h e p a r a s i t e d e p e n d s o n u p t a k e from t h e host for its p o l y a m i n e supply.
An i n t e r c o n v e r s i o n p a t h w a y f o r p o l y a m i n e s h a s b e e n d e m o n s t r a t e d w h i c h d o e s n o t i n v o l v e t h e p o l y a m i n e N - a c e - tyltransferase, t h e rate limiting s t e p in t h e i n t e r c o n v e r s i o n o f p o l y a m i n e s in m a m m a l s . A n o v e l t y p e o f p o l y a m i n e o x i d a s e h a s b e e n identified w h i c h is s o l e l y r e s p o n s i b l e for t h e i n t e r c o n v e r s i o n a n d d e g r a d a t i o n o f p o l y a m i n e s . In addition, a p a r a s i t e - s p e c i f i c N - a c e t y l t r a n s f e r a s e for p u t r e s c i n e w a s found w h i c h is involved in t h e d e g r a d a t i o n a n d e x c r e t i o n o f e x c e s s p o l y a m i n e s .
D e p l e t i o n o f p o l y a m i n e levels in filarial w o r m s is thought t o h a v e c y t o s t a t i c i f n o t c y t o t o x i c e f f e c t s , a s h a s b e e n s h o w n previously in t h e c h e m o t h e r a p y o f c a n c e r a n d p r o t o z o a n infections b y D L - a - d i f l u o r o m e t h y l o r n i t h i n e ( D F M O ) . Filarial w o r m s a n d o t h e r h e l m i n t h s l a c k o r n i t h i n e d e c a r b o x y l a s e , t h e t a r g e t f o r D F M O . T h u s , a s t h e p a r a s i t e d e p e n d s o n t h e u p t a k e o f p o l y a m i n e s from t h e h o s t tissues, inhibition o f transport m e c h a n i s m s resulting in rapid d e p l e tion o f p o l y a m i n e s s h o u l d b e e x p l o i t a b l e for c h e m o t h e r a p y .
* D e p a r t m e n t o f B i o c h e m i c a l Parasitology, B e r n h a r d Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, 20359 Hamburg. Germany.
** Department o f Medical Parasitology. London School o f Hygiene
& Tropical Medicine, Keppel St, London, WC1E 7HT, U.K.
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Article available athttp://www.parasite-journal.orgorhttp://dx.doi.org/10.1051/parasite/199401s1060b
V E C T O R B I O L O G Y
P o l y a m i n e a n a l o g u e s , e . g . fc^XbenzyDpolyamine ( M D L 2 7 6 9 5 ) , a l t h o u g h s h o w n t o i n t e r f e r e s t r o n g l y w i t h b o t h p o l y a m i n e u p t a k e s y s t e m s o f filarial w o r m s , p r o b a b l y e x h i bit their filaricidal effects by c o m p e t i n g a n d interacting with p o l y a m i n e b i n d i n g sites s u c h as n u c l e i c a c i d s a n d structural m a c r o m o l e c u l e s .
Inhibition o f S - a d e n o s y l m e t h i o n i n e d e c a r b o x y l a s e , a regula
tory a n d rate-limiting s t e p in the b i o s y n t h e s i s o f p o l y a m i n e s w h i c h p r o v i d e s the a m i n o p r o p y l g r o u p for the synthesis o f s p e r m i d i n e a n d s p e r m i n e , r e s u l t s in d e p l e t i o n o f p o l y a m i n e s . MDL 7 3 8 1 1 , an irreversible inhibitor o f S-adenosyl
m e t h i o n i n e d e c a r b o x y l a s e , affects b o t h p o l y a m i n e synthesis a n d the viability o f n e m a t o d e s m a i n t a i n e d in vitro.
T h e strategy p r o p o s e d h e r e is d i r e c t e d t o the i n t e r c o n v e r - s i o n a n d d e g r a d a t i o n p a t h w a y f o r p o l y a m i n e s . T h i s is b a s e d o n t h e findings that t h e p o l y a m i n e o x i d a s e is t h e rate-limiting s t e p for t h e b a c k c o n v e r s i o n o f s p e r m i n e t o s p e r m i d i n e a n d p u t r e s c i n e a n d that e l e v a t e d levels o f sper
m i n e a r e lethal for Brugia w o r m s m a i n t a i n e d in vitro. T h e potential o f p o l y a m i n e o x i d a s e as a target for c h e m o t h e rapy has b e e n a s s e s s e d by treatment o f Brugia a n d Ascaris w o r m s with MDL 7 2 1 4 5 , an irreversible inhibitor o f n e m a
T O D E p o l y a m i n e o x i d a s e , which resulted in e n z y m e inactiva- t i o n a n d a s u b s e q u e n t a c c u m u l a t i o n o f s p e r m i n e . B y structural analysis o f the filarial p o l y a m i n e o x i d a s e a n d the isofunctional m a m m a l i a n e n z y m e , differences m a y b e iden
tified a n d e x p l o i t e d for the synthesis o f drugs w h i c h react selectively with the parasite e n z y m e .
Figure 1.
VECTOR BIOLOGY
H U M O R A L D E F E N S E MOLECULES I N VEC
T O R S O F F I L A R I A S I S
HAM P.J.*, HAGEN H.E.*, SMITHIES B.M.*, CHALK R. AND A L B U Q U E R Q U E C.M.R.*
KEYWORDS : insect immunity, defense. Onchocerca, humoral proteins.
I N T R O D U C T I O N
T
h e relationship b e t w e e n the definitive host, man, a n d filarial parasites, has for l o n g b e e n a subject o f i n t e n s e study, a n d as this n e t w o r k attests, still is today. H o w e v e r , the interactions b e t w e e n v e c t o r s o f l y m p h a t i c filariasis a n d o n c h o c e r c i a s i s a n d t h e s e n e m a t o d e s , is l e s s w e l l u n d e r s t o o d . T h e r e is n o w a c o n s i d e r a b l e b o d y o f data d e s c r i b i n g the i n n a t e a n d a c q u i r e d r e s i s t a n c e o f v e c t o r s t o the parasites they carry ( e g . r e v i e w e d b y T o w n s o n a n d C h a i t h o n g , 1 9 9 3 ; C h r i s t e n s e n a n d S e v e r s o n 1 9 9 3 ; H a m , 1 9 9 2 ) . B l a c k f l i e s a n d m o s q u i t o e s p o s s e s s c o m p l e x i m m u n e s y s t e m s , c o m p r i s i n g inter-related cellular a n d h u m o r a l c o m p o n e n t s . Not o n l y is immunity e x p r e s s e d in the h a e m o c o e l , but m e c h a n i s m s o f refractoriness a l s o a p p e a r t o b e l i n k e d
* Centre for Applied Entomology and Parasitology. Department of Biological Sciences, Keele University, Staffordshire, S T 5 5 B G , U.K.
t o gut l u m e n c o m p o n e n t s ( s e e r e v i e w Ham, 1 9 9 2 ) a n d t h o racic tissues ( W a t t a m & Christensen, 1 9 9 2 ) .
R E S P O N S E S T O I N F E C T I O N
T
h r e e g e n e r a l i s e d r e s p o n s e s a p p e a r to t a k e p l a c e follow i n g infection o f insects : ( 1 ) an alteration in m e t a b o l i c activity, including protein synthesis, ( 2 ) induction o f s p e c i fic i m m u n e p e p t i d e s a n d p r o t e i n s s o m e o f w h i c h h a v e pro
t e c t i v e f u n c t i o n a l a n t i b i o t i c a c t i v i t y , a n d ( 3 ) e n h a n c e d h a e m o c y t i c proliferation. T h i s proliferation m a y b e a s s o c i a t e d with i n c r e a s e d s e c r e t i o n o f m o l e c u l e s in ( 2 ) ( F i g u r e 1 ) . As w e l l as r e s p o n s e s to infection, insects, including v e c t o r s o f filariasis m a y e x h i b i t r e s p o n s e s to others forms o f stress s u c h as c o l d , o v e r c r o w d i n g a n d p h y s i c a l t r a u m a s u c h as injury ( e g K o m a n o et al., 1 9 8 0 ) .
H U M O R A L D E F E N S E M O L E C U L E S
^ n u m b e r o f d e f e n s e p e p t i d e s h a v e b e e n o b s e r v e d in 1 1 insects, a n d m a n y o f t h e s e are k n o w n to b e induced by bacterial p a t h o g e n s s u c h as Escherichia coli, as well as filariae ( s e e Figure 2 w h i c h s h o w s i m m u n e and n o n i m m u n e
