INTRODUCTION:
Oral cancer is a major form of cancer worldwide and is
one of the most common malignancy in India accounting for 30-40 per cent of all
cancers[1, 2]. Tobacco chewing with betel quid, tobacco smoking and alcohol
consumption are the most important aetiological factors associated with the
incidence of oral cancer in India [3]. An antioxidant is a molecule which
inhibits oxidation reaction. Antioxidants terminate the chain reaction caused
by free radicals of oxidation reaction , preventing cell damage or death of the
cells. Insufficient levels of antioxidants or inhibition of antioxidant enzymes
causes oxidative stress and damage or kill the cells. It has been suggested
that negative effects of nicotine are reversed by antioxidants [4].
oxygen species plays an effective role in the
pathogenesis of different pathological diseases including cancer[5,6]. Harmful
effects of ROS are balanced by enzymatic and non enzymatic antioxidants [7].
The successful control of oral cavity cancer will depend on its prevention.
Cessation of tobacco use is a primary objective in this. endeavor. Additionally,
considerable evidence exists suggesting a role for nutrients, particularly the so-called
anti-oxidants, beta-carotene and vitamin E, in the prevention of this disease [8].
Free radicals
and their role in oral cavity cancer:
Free radicals
are highly reactive chemicals that have the potential to harm cells. They are
created when an atom or a molecule either gains or loses an electron. Free
radicals are formed naturally in the body and play an important role in many
normal cellular processes [9,10]. At high
concentrations, however, free radicals can be hazardous to the body and damage
all major components of cells, including DNA, proteins, and cell membranes. The
damage to cells caused by free radicals, especially the damage to DNA, may play
a role in the development of cancer.
ROS include both free radicals as well as non-radical
derivative sofoxygen [11]. Therelation between free radicals and disease can be
explained by the concept of ‘oxidative stress’ elaborated by Sies [12]. He defined
oxidative stress as an imbalance between oxidants and antioxidants in favour of
oxidants, potentially leading to damage [13]. Initiation of cancer by ROS is
supported by presence of oxidative DNA modifications in cancer tissues [14].
The promotion stage is characterized by clonal expansion of initiated cells, by
induction of cell proliferation and/or inhibition of apoptosis [15]. Oxidative
stress is strongly involved in this stage.
Chemically, oxidative stress is associated with
increased production of oxidizing species or a significant decrease in the
effectiveness of antioxidant defenses, such as glutathione [16]. The effects of oxidative stress depend upon the size
of these changes, with a cell being able to overcome small perturbations and
regain its original state. However, more severe oxidative stress can cause cell
death and even moderate oxidation can trigger apoptosis, while more intense stresses may causes necrosis [17].
Free radicals are highly reactive and are capable of
damaging almost all types of biomolecules [18,19].
Tobacco chewing
and smoking
causes imbalance level of oxidant-antioxidant which increases oxidative stress.
It disturbs the antioxidant defence which can induce the malignant process
hence leading to oxidative DNA damage, damage to macro and micro-molecules of
cells and increase in lipid peroxidation. Does intake of tobacco affects the
formation and stabilisation of free radicals [20]. The fact is that free
radicals be get free radicals, i.e., generate free radicals from normal
compounds which continue as a chain reaction.
Antioxidant and
their role in prevention of cancer:
Antioxidants
are chemicals that interact with and neutralize free radicals,
thus preventing them from causing damage. Antioxidants are also known as “free radical scavengers”.
The body makes some of the antioxidants it
uses to neutralize free radicals. These antioxidants are called endogenous
antioxidants. However, the body relies on external (exogenous) sources,
primarily the diet, to obtain the rest of the antioxidants it needs. These
exogenous antioxidants are commonly called dietary antioxidants. Fruits,
vegetables, and grains are rich sources of dietary antioxidants. Some dietary
antioxidants are also available as dietary
supplements [9, 21].
Antioxidants according to their location:
The following are some antioxidants according to their
location [22, 23]:
(i) Plasma antioxidants: β-carotene,
ascorbic acid, bilirubin, uric acid, ceruloplasmin, transferring.
(ii) Cell membrane antioxidants: α-tocopherol.
(iii) Intra-cellular antioxidants: superoxide
dismutase, catalase, glutathione peroxidase.
The important Antioxidant is
β-carotene, A precursor of vitamin A has antioxidant and free radical
scavenging property. It also helps in immunomodulation, promotes increase in
the numbers of T-helper and NK cells as well as cells with IL-2 receptors and
inhibits mutagenesis and cancer cell growth [24-29].
The mineral element selenium
is often thought to be a dietary antioxidant, but the antioxidant effects of
selenium are most likely due to the antioxidant activity of proteins that have
this element as an essential component (i.e., selenium-containing proteins) and
not to selenium itself [30].
Many observational
studies, including case–control
studies and cohort
studies, have been conducted to investigate whether the use of
dietary antioxidant supplements is associated with reduced risks of cancer in
humans. Overall, these studies have yielded mixed results [31].
CONCLUSION:
Antioxidant level in our
health is low which causes increase in oral cancer Intake of dietary
antioxidants protect us from the harmful effects of free radicals. Foods with
high antioxidants nutrients play a major role in disease prevention. It appears
that diets low in antioxidant vitamins cannot only increase the risk of
developing gum disease but influence its severity as well. Antioxidants
supplements were once thought to be harmless but increasingly we are becoming
aware of their interactions and potential toxicity.
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