Abstract
BackgroundOur interest was to find out whether pineal gland and their by melatonin act as modulator of immunosenescence. Parachlorophenylalanine (PCPA) – a β adrenergic blocker, is known to perform chemical pinealectomy (Px) by suppressing indirectly the substrate 5-hydroxytryptamine (5-HT) for melatonin synthesis and thereby melatonin itself. The role of PCPA, alone and in combination with melatonin was recorded in immunomodulation and free radical load in spleen of young adult and aged seasonal breeder Indian palm squirrel Funambulus pennanti.ResultsAged squirrel presented reduced immune parameters (i.e. total leukocyte count (TLC), Lymphocytes Count (LC), % stimulation ratio of splenocytes (% SR) against T cell mitogen concanavalin A (Con A), delayed type hypersensitivity (DTH) to oxazolone) when compared to young adult group. Melatonin administration (25 μg/100 g body mass/day) significantly increased the immune parameters in aged more than the young adult squirrel while PCPA administration (4.5 mg/100 g body mass/day) reduced all the immune parameters more significantly in young than aged. Combination of PCPA and melatonin significantly increased the immune parameters to the normal control level of both the age groups. TBARS level was significantly high in aged than the young group. PCPA treatment increased TBARS level of young and aged squirrels both while melatonin treatment decreased it even than the controls. Nighttime peripheral melatonin level was low in control aged group than the young group. Melatonin injection at evening hours significantly increased the peripheral level of nighttime melatonin, while combined injection of PCPA and melatonin brought it to control level in both aged and young adult squirrels.ConclusionPCPA suppressed immune status more in aged than in adult by reducing melatonin level as it did chemical Px. Melatonin level decreased in control aged squirrels and so there was a decrease in immune parameters with a concomitant increase in free radical load of spleen. Decreased immune status can be restored following melatonin injection which decreased free radical load of spleen and suggest that immune organs of aged squirrels were sensitive to melatonin. Increased free radical load and decreased peripheral melatonin could be one of the reasons of immunosenescence.
Highlights
Our interest was to find out whether pineal gland and their by melatonin act as modulator of immunosenescence
A combined treatment of melatonin along with PCPA significantly (P < 0.01) increased the spleen weight of aged squirrels only without affecting the spleen weight of young adult squirrel when compared with their respective controls
Melatonin alone given to the aged squirrels showed a significant (P < 0.01) increase in spleen weight when compared with control, PCPA and PCPA plus melatonin treated groups (Figure 1)
Summary
Our interest was to find out whether pineal gland and their by melatonin act as modulator of immunosenescence. Melatonin (N-acetyl-5-methoxytryptamine) is synthesized mainly in pineal gland. It plays a major role in regulating sexual maturity, reproductive cycle, stress and the immune responses [1,2,3]. Aging is associated with a decline in immune function known as immunosenescence. Melatonin has been demonstrated to bear a general immune-enhancing effect in many animal species including humans [9]. Whether this immune- enhancing property of melatonin exists in aged animals needs to be verified. Disruption of the night – time peak of melatonin completely abolished Colony Forming Unit- Granulocyte Macrophages (CFUGM) proliferation of bone marrow cells [11,12]
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