Ebenezer T. Oriaku

Ibuprofen and apigenin induce apoptosis and cell cycle arrest in activated microglia

In case of injury or disease, microglia are recruited to the site of the pathology and become activated as evidenced by morphological changes and expression of pro-inflammatory cytokines. Evidence suggests that microglia proliferate by cell division to create gliosis at the site of pathological conditions such as the amyloid plaques in Alzheimers disease and the substantia nigra of Parkinsons disease patients. The hyperactivation of microglia contributes to neurotoxicity. In the present study we tested the hypothesis that anti-inflammatory compounds modulate the progression of cell cycle and induce apoptosis of the activated cells. We investigated the effects of ibuprofen (non-steroidal anti-inflammatory drug) and apigenin (a flavonoid with anti-inflammatory and anti-proliferative properties) on the cell cycle of the murine microglial cell line BV-2. The findings indicate that apigenin-induced cell cycle arrest preferentially in the G2/M phase and ibuprofen caused S phase arrest. The binding of annexin V-FITC to the membranes of cells which indicates the apoptotic process were examined, whereas the DNA was stained with propidium iodide. Both apigenin and ibuprofen induced apoptosis significantly in early and late stages. The induction of apoptosis by ibuprofen and apigenin was confirmed using TUNEL assay, revealing that 25 microM apigenin and 250 microM ibuprofen significantly increased apoptosis in BV-2 cells. The results from the present study suggest that anti-inflammatory compounds might inhibit microglial proliferation by modulating the cell cycle progression and apoptosis.

The potentiating effects of 1-methyl-4-phenyl-1,2,3,6 -tetrahydropyridine (MPTP) on paraquat-induced neurochemical and behavioral changes in mice

Although the etiology of Parkinsons disease (PD) is not fully understood, there are numerous studies that have linked the increased risk for developing PD to pesticides exposure including paraquat (PQ). Moreover, the exposure to a combination of compounds or chemical mixtures has been suggested to further increase this risk. In the current study, the effects of PQ on the nigrostriatal dopaminergic system in male C57BL6 mice exposed to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were examined to assess the impact of toxic substance mixtures exposure on neurochemical and behavioral changes. In this study, a low non-toxic dose of MPTP (10mg/kg) was injected once a day for 5 days and was followed by PQ (7 mg/kg) once a day for 6 days (subacute protocol) or once a week for 10 weeks (chronic protocol). The results from the subacute protocol showed that PQ reduced the turnover of dopamine (DA) as indicated by a 21% and a 22.3% decrease in dihydroxyphenyl acetic acid (DOPAC), homovanillic acid and increased S-adenosyl methionine/S-adenosyl homocysteine index (SAM/SAH) by 100%. However, the administration of PQ to MPTP primed mice resulted in the decrease of DOPAC, HVA, DA, by 35.8%, 35.2% and 22.1%, respectively. In addition, PQ decreased the total number of movements (TM) by 28% but MPTP plus PQ decreased TM by 41%. The SAM/SAH index showed that MPTP increased methylation by 33.3%, but MPTP plus PQ increased methylation by 81%. In the chronic protocol, the data showed that MPTP administration did not affect DA, DOPAC, and HVA levels. The administration of PQ led to significant decrease in DOPAC, HVA, and TD by 31.6%, 19.9%, and 21.2% respectively with no effect on DA levels. The MPTP plus PQ group showed reduced DA, DOPAC, HVA, and total distance traveled by 58.4%, 82.8%, 55.8%, and 83.9%, respectively. Meanwhile, PQ administration caused a reduction in tyrosine hydroxylase immunoreactivity in the substantia nigra, and this effect was more pronounced in MPTP pretreated mice. It was concluded from this study that prior treatment with MPTP potentiated the effects of PQ in reducing DA, DOPAC, HVA, TH immunoreactivity, locomotor activity, and increasing the methylation index. The enhanced effects of PQ following MPTP administration further support the role of toxic substance mixtures in causing Parkinsons disease.

Diallyl trisulfide as an inhibitor of benzo(a)pyrene-induced precancerous carcinogenesis in MCF-10A cells

Diallyl trisulfide (DATS) is a garlic organosulfide that is toxic to cancer cells, however, little is known about its effect in the initiation phase of carcinogenesis. We sought to determine whether DATS could inhibit the carcinogen, benzo(a)pyrene (BaP), from inducing precancerous activity, in vitro. MCF-10A cells were either pre-treated (PreTx) or concurrently treated (CoTx) with 1 μM BaP, and 6 or 60 μM DATS for up to 24h. The DATS 6 and 60 μM CoTx inhibited BaP-induced cell proliferation by an average of 71.1% and 120.8%, respectively, at 6h. The 60 μM DATS pretreatment decreased BaP-induced G2/M cell cycle transition by 127%, and reduced the increase in cells in the S-phase by 42%; whereas 60 μM DATS CoTx induced a 177% increase in cells in G1. DATS effectively inhibited (P<0.001) BaP-induced peroxide formation by at least 54%, which may have prevented the formation of BaP-induced DNA strand breaks. In this study, we reveal mechanisms involved in DATS inhibition of BaP-induced carcinogenesis, including inhibition of cell proliferation, regulation of cell cycle, attenuation of ROS formation, and inhibition of DNA damage. At the doses evaluated, DATS appears to be an effective attenuator of BaP-induced breast carcinogenesis, in vitro.

The attenuation of early benzo(a)pyrene-induced carcinogenic insults by diallyl disulfide (DADS) in MCF-10A cells

Diallyl disulfide (DADS), a garlic organosulfur compound, has been researched as a cancer prevention agent; however, the role of DADS in the suppression of cancer initiation in nonneoplastic cells has not been elucidated. To evaluate DADS inhibition of early carcinogenic events, MCF-10A cells were pretreated (PreTx) with DADS followed by the ubiquitous carcinogen benzo(a)pyrene (BaP), or cotreated (CoTx) with DADS and BaP for up to 24 h. The cells were evaluated for changes in cell viability/proliferation, cell cycle, induction of peroxide formation, and DNA damage. BaP induced a statistically significant increase in cell proliferation at 6 h, which was attenuated with DADS CoTx. PreTx with 6 and 60 μM of DADS inhibited BaP-induced G2/M arrest by 68% and 78%, respectively. DADS, regardless of concentration or method, inhibited BaP-induced extracellular aqueous peroxide formation within 24 h. DADS attenuated BaP-induced DNA single-strand breaks at all time points through both DADS Pre- and CoTx, with significant inhibition for all treatments sustained after 6 h. DADS was effective in inhibiting BaP-induced cell proliferation, cell cycle transitions, reactive oxygen species, and DNA damage in a normal cell line, and thus may inhibit environmentally induced breast cancer initiation.

Effect of Ethanol on the Rat Gastrointestinal Cholinergic Enzymes

Male Sprague-Dawley rats weighing between 180 and 220 g and maintained under controlled lighting and temperature conditions were used in this experiment. Animals were given ethanol (3 g/kg, p.o.) 24 h after fasting. One group was given ethanol at 10.00 h (light phase) and the other at 22.00 h (dark phase). One hour later, the treated animals with their proper controls were sacrificed and the mucosa of the stomach, duodenum, ileum and colon were separated and assayed for choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities. Data obtained indicate that the administration of ethanol resulted in significant decline (p less than 0.01) in ChAT activity in the stomach and the colon during the light phase. A significant increase (p less than 0.01) in ChAT activity was also noted in the ileum during the dark phase. There was a significant decrease (p less than 0.01) in AChE activity in the stomach during the dark phase. The administration of ethanol also resulted in a significant decline in AChE activity (p less than 0.05) in the duodenum and the colon (p less than 0.01). The results obtained indicate that the gastrointestinal changes caused by ethanol administration may be related to changes in the cholinergic enzymes of the mucosa of the gastrointestinal tract.

Brain cholinergic involvement during the rapid development of tolerance to morphine

In this study, male Sprague-Dawley rats maintained under controlled environmental conditions were used. Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities were determined in cerebral cortex, bulbus olfactorius, midbrain, hypothalamus, hippocampus, cerebellum, pons and medulla oblongata in control rats and rats treated with morphine (10 mg/kg) for 1 or 2 days. Repeated administration of morphine was associated with a decline in the degree of analgesia produced. Significant increase (p less than 0.01) in AChE activity of the medulla oblongata was observed following morphine administration for 1 or 2 days. A single injection of morphine resulted in a significant decline (p less than 0.01) in ChAT activity of hypothalamus, cerebellum and medulla oblongata. However, no such decline could be observed after 2 consecutive daily injections of morphine. In the cerebral cortex there was a significant decline (p less than 0.01) in ChAT activity after the second administration of morphine. These findings indicate that the changes in the responsiveness of the brain cholinergic enzymes following repeated morphine administration may in part explain the rapid development of tolerance to the analgesic effect of morphine.

EFFECTS OF DIETARY RESTRICTION ON INSULIN RESISTANCE IN OBESE MICE

In many cases, development of insulin resistance has been linked to obesity and may contribute to mechanism of aging. The role of diet, irrespective of degree of obesity, in modulating insulin resistance and development of age degeneration disease remains uncertain. Lowered blood glucose levels are commonly associated with diet restriction (DR), which is an intervention shown to successfully retard aging and age associated disease. The effects of DR on blood glucose and insulin resistance were measured in yellow obese (Avy/A), lean black (a/a) mice and in another common inbred strain (B6C3F1) (at three different ages). The yellow obese mice become diabetic as a result of an insulin receptor defect which is not clearly understood. Insulin responses and radioinsulin binding were assayed in yellow obese and lean black mice fed either ad libitum (AL) or DR diets (YAL, BAL, YDR and YAL, respectively) at four different circadian intervals. The B6C3F1 controls were fed either AL (CAL) or DR (CDR) and measures were made at six circadian stages and three different ages. Within 23 days, DR produced a significant loss in body weight and a time-dependent 22–55% reduction in basal blood glucose levels in the yellow obese mice. Additionally, exogenous insulin produced circadian stage dependent (at the time of food intake) reductions in blood glucose in the YDR animals that were not present in YAL animals. 125I-Insulin binding in liver was increased nearly 2-fold in YDR and BDR mice during the time of day that animals were active and eating. 125I-Insulin binding was two-fold-higher in CDR mice at 4, 12 and >24 months of age. Binding decreased as a function of age in both the CAL and CDR animals. However, even in the >24 month group the CDR animals were found to have levels of binding that were as high as those found in younger CAL liver. The mechanism of action appears to be through resolution of insulin resistance by modulating an insulin receptor defect.

Brain cholinergic involvement in the diurnal variations of the rapid development of tolerance to the hypothermic effect of apomorphine.

Male Sprague-Dawley rats maintained under controlled environmental conditions were used. Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities were determined in the cerebral cortex, bulbus olfactorius, midbrain, hypothalamus, hippocampus, cerebellum, pons and medulla oblongata of control rats and rats treated with apomorphine (15 mg/kg, i.p.) after a single dose or after a second dose administered 24 h later at 10.00 or 22.00 h. Results of this experiment indicate that the repeated administration of apomorphine at 10.00 h was associated with rapid development of tolerance to the hypothermic action of this drug. A single injection of apomorphine resulted in significant (p less than 0.01) decrease of AChE and significant increase of ChAT activity (p less than 0.01) in the cortex, hypothalamus and pons. There were no significant differences between tolerant and control animals in the activities of AChE or ChAT in the bulbus olfactorius, cerebral cortex, midbrain, pons or medulla. On the other hand, repeated administration of apomorphine at 22.00 h was not associated with tolerance to the hypothermic action of this drug. A single injection of apomorphine at 22.00 h resulted in significant (p less than 0.01) increase in AChE activity of the midbrain, hippocampus, and the medulla oblongata with no significant changes in the cerebral cortex and bulbus olfactorius. There was a significant decline (p less than 0.01) of ChAT activity of the hypothalamus, hippocampus, cerebral cortex and the medulla oblongata (p less than 0.05). Meanwhile, there was a significant (p less than 0.05) increase of ChAT activity of the midbrain with no significant changes in the cerebellum, pons and the bulbus olfactorius.(ABSTRACT TRUNCATED AT 250 WORDS)