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Biokemistri
Nigerian Society for Experimental Biology
ISSN: 0795-8080
Vol. 16, Num. 1, 2004, pp. 23-27
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Biokemistri, Vol. 16, No.1, June, 2004, pp.23-27
Metal binding acute phase proteins and trace elements in Nigerian children
with urinary schistosomiasis.
Olatunbosun G. ARINOLA
Department of Chemical Pathology and Immunology, College of Medicine, University
of Ibadan, Nigeria.
E-mail: arinolaog@doctor.com, Tel: 08023451520
Received 19 November 2003
Code Number: bk04004
Abstract
Fifty-five Nigerian children with urinary schistosomiasis (USS) and 34
apparently healthy children of matched ages and sexes were considered for
this study. In these children, metal binding acute phase proteins (transferrin
and caeruloplasmin) and trace elements were measured by single radial immunodiffusion
and atomic absorption spectrophotometry respectively. The result shows
that Cd, Mn, albumin and transferrin were reduced (p<0.01, p>0.20,
p<0.01 and p<0.01 respectively) while Fe, Cu and caeruloplasmin were
raised (p<0.01, p<0.01 and p<0.01 respectively) in USS subjects
when compared with the controls. Low levels of transferrin might be responsible
for raised level of plasma Fe, which is in turn modulated by caeruloplasmin.
It may be concluded that trace elements and antioxidants are involved in
the pathogenesis of USS.
Key words: Schistosomiasis, elements, proteins, antioxidants, children.
INTRODUCTION
There are various effector mechanisms needed to attack different stages
of schistosome infections. Schistosomal worms are damaged at high levels
of antibodies and complement factors but low levels of antibody sensitizes
neutrophils, macrophages, eosinophils and platelets for antibody-dependent
cell-mediated cytotoxicity. Neutrophils and macrophages act by releasing
toxic reactive oxygen species and nitric oxide (NO) whereas eosinophils damage
the schistosome tegument by the release of major basic proteins (1).
Reactive oxygen species and NO which are parts of immune responses against Schistosoma
haematobium parasites may also lead to consumption/reduction of antioxidants,
or when produced in excess amount may damage surrounding cells and autotoxicity
in some cases (2). Prostaglandin E2 (a critical immunimodulator) is produced
in the pathway involving the production of NO via L-arginine pathway (3).
The most potent of the reactive O2 species (ROS) are OH. ,
O2. , HO2. ,
HOCl and H2O2, all of which are generated during
oxidative burst by phagocytic neutrophils and macrophages. These ROS are
also released in relatively high concentrations during inflammation (4).
Inflammation is a common phenomenon in urinary schistosomiasis. However,
there are several naturally occurring compounds (antioxidants) that can inactivate/lower
these ROS. Antioxidants may be preventive type (such as catalase, transferrin,
caeruloplasmin and albumin) or chain breaking type (such as superoxide dismutase,
uric acid, vitamin C and bilirubin) (5).
Previous studies showed that during USS, there is inflammation and production
of ROS and NO by phagocytes. It is likely therefore that the levels of antioxidants
and trace metals may be affected by Schistosoma haematobium infection.
The present study is designed to assess the levels of preventive antioxidants
and trace elements in Nigerians with USS.
MATERIALS AND METHODS
USS Subjects: Before the commencement of the study ethical approval
was obtained from UCH/UI Ethical Review Committee. A total of 84 Nigerian
(aged between 4-15 years) children were involved in the study. Among these
are 54 children with USS. Schistosoma. haematobiuminfection was identified
by location of terminal spined eggs in the urine as previously described
(6).
Controls: Forty-three Schistosoma haematobium free subjects
who were age and sex matched with the USS subjects formed the control group.
The subjects (USS and controls) with heavy malaria, microfilaria and intestinal
helminth infections were excluded from the study. Microfilaria was examined
in thick blood films stained with Giemsa while intestinal helminthes eggs
were examined in normal saline preparation of faecal samples stained with
Dobell iodine (6).
Determination of acute phase proteins: The motive behind the study
was explained to each subject before sample collection. Five (5) ml of venous
blood was withdrawn from each subject. Two ml (2ml) of the blood was put
into a plain glass universal bottle for the determination of acute phase
proteins, while the remaining 3 ml was put into bottle containing lithium
heparin for the determination of trace elements. Serum concentrations of
transferrin and caeruloplasmin were estimated using single radial immunodiffusion
method (7) while albumin was determined using bromocresol green solution
as described by Varley (8). This was based on the principle that peptide
linkages in the amino acids which make up a protein are capable of reacting
with copper in alkaline solution to produce a violet colour (8).
Plasma concentrations of trace metals: This was determined by atomic
absorption spectroscopy as described (9). In the vapourised ground state
(unexcited), atom of a trace metal absorb light of the same wavelength as
that emitted by the metal in the excited state. The amount of light absorbed
is proportional to the trace metal in the solution (9).
Statistical analysis: Statistical analysis was performed by calculating
the mean, standard deviation and Students t test.
RESULTS
Table 1 showed that iron and copper were significantly raised (p<0.01
in each case) in USS subjects compared with the controls. Both cadmium and
manganese were reduced in USS subjects but the difference was significant
in the level of cadmium only. Caeruloplasmin was significantly raised (p<0.01)
in USS while both albumin and transferrin were significantly reduced (p<0.01
in each case) in USS subjects compared with the controls.
DISCUSSION
The results of the study showed significantly reduced levels of albumin
and transferrin and significantly elevated level of caeruloplasmin in USS
subjects compared with the controls. This is a confirmation that inflammation
is present in USS subjects and this might have been caused by tissue damage
resulting from schistosome eggs, migrating larva and adult worms. Acute phase
proteins are synthesized in the liver hence their increase in the plasma
may be deduced from increased synthesis (10). This suggests that adequate
synthetic function of the liver is maintained in USS subjects.
Decreased level of transferrin detected in USS subjects may be due to its
consumption by schistosome larva as well as inflammatory responses during
tissue damage by schistosome eggs. Schistosome larva uses transferrin and
albumin as growth factors (7). Also transferrin is a negative acute phase
reactants whose level decreases with inflammation. Under normal condition
most of the iron are bind to transferrin leaving a small concentration of
free iron in the plasma. Low level of transferrin in the present study could
mean that, there might be excess unbound iron in the plasma. This might explain
the significantly raised concentration of iron observed in USS subjects considered
for this study.
Table 1: Concentrations of trace elements and metal binding acute phase
proteins in urinary schistosomiasis subjects.
USS(n=55) Controls(n=34) t p
Fe (mg/dL) 159.9 ± 4.9 156.5 ± 3.5 3.78 <0.01
Cd (mM/L) 32.1 ± 7.5 36.2 ± 5.4 2.97 <0.05
Cu (µg/ml) 146.5 ± 26.1 122.1 ± 23.7 4.51 <0.01
Mn (mg/dL) 4.83 ± 3.3 5.35 ± 2.8 0.79 >0.20
Albumin(g/dL) 3.37 ± 0.3 3.98 ± 0.41 7.63 <0.01
Caeruloplasmin(mg/dL) 35.9 ± 8.1 31.2 ± 5.8 3.36 <0.01
Transferrin(mg/dL) 200.1 ± 8.4 206 ± 3.3 4.54 <0.01
Values are in x ± s.d
The relationship between iron level and the effects of iron on the virulence
of specific pathogens and host-immune functions is complex. Enhanced growth
of infectious agents is a major concern for iron supplementation in iron
deficient individuals (10). Direct alterations in immune function are associated
with excess iron and alteration in neutrophil defense in haemodialized patients
with iron overload have been reported (11). Excessive production of toxic
O2 species in response to high cellular iron contribute to decreased
phagocytosis (12). Decreased natural killer cell (NKC) activity in response
to multiple transfusions in thalassemia patients has been reported (13).
Studies described elsewhere-detected slightly reduced leucocyte ingestion
and digestion rates in Nigerian USS subjects (6). The raised iron level may
explain these observations.
Caeruloplasmin is reported to be involved in iron metabolism and copper
transport (14). Significantly elevated level of caeruloplasmin in USS subjects
compared with the controls may be as a result of inflammation and additional
need for caeruloplasmin as a result of copper and iron increases. Caeruloplasmin
is an O2 radical scavenger and polymorphonuclear phagocytes produce
free O2 radicals during intracellular killing of ingested particles
(15). Excess free O2 radicals will require corresponding amount
of caeruloplasmin (among other O2 radical scavengers) for its
clearance. Therefore, increased caeruloplasmin in the USS subjects may be
concluded since it will control the level of excessive concentration of plasma
iron and copper in USS subjects. Copper is among the most toxic of the trace
elements and was raised in USS subjects. Excessive circulatory copper result
in the generation of reactive O2 radicals and peroxides, thus
there is need for its removal from biological systems.
Manganese activates glycosyl transferases that are necessary for polysaccharide
and glycoprotein synthesis. Manganese is also involved in cholesterol and
protein biosynthesis and alleviation of blood clotting defects (16). Insignificant
reduction in manganese levels in USS subjects could be supported by reduced
synthesis of protein as indicated by significant reduced level of albumin.
This reduction could be explained by raised level of iron since a study showed
that individuals with low manganese status may be at risk of excess iron
than those with adequate amount (17).
Low concentration of cadmium was detected in USS subjects. High concentration
of cadmium is toxic to polymorphonuclear neutrophils (18), decreased phagocytic
function of macrophages, increased production of NO, O2. and
H2O2 but most of these effects are alleviated by addition
of selenium (19). The low level of cadmium in USS subjects is not therefore
too dangerous.
Albumin was found to be reduced in USS subjects. This result is in line
with Hussain et al (20) where hypoalbuminaemia in schistosomiasis was reported.
The cause of reduced albumin may be one of the following reasons: protein
loss in the urine, being a negative acute reactant and consumption by schistosome
larva. Albumin regulates the oncotic pressure of the blood; it binds and
transports metal ions, drugs, amino acids and toxic wastes among others.
The consequence of albumin deficiency in USS is detrimental since free and
toxic forms of these substances may be predominant in the blood.
This study suggests a possible involvement of trace elements and antioxidants
in the pathogenesis of USS.
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© 2004 Nigerian Society for Experimental Biology.
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