Hydroxyurea Exposure and Development of the Cerebellar External Granular Layer: Effects on Granule Cell Precursors, Bergmann Glial and Microglial Cells

Protective potential of royal jelly against hydroxyurea -induced hepatic injury in rats via antioxidant, anti-inflammatory, and anti-apoptosis properties

Hydroxyurea (HDU) is a widely used medication for various malignancies, thalassemia, and sickle cell anemia with reported side effects. The current study investigated HDU- induced hepatic injury and the protective potential of the royal jelly (RJ) against this hepatotoxic effect in the light of hepatic oxidative/ antioxidative status, pro-inflammatory cytokine, apoptosis signaling pathway, and histopathology. Sixty albino rats were used (n = 10/group) for 60 days: control, RJ (100 mg/kg body weight, orally), HDU (225 mg/kg body weight, orally), 2HDU (450 mg/kg body weight, orally), and HDU + RJ groups. HDU-treated rats showed significant elevation of liver function tests as aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase, as well as malondialdehyde and nitric oxide (oxidative biomarkers) and significant decreased hepatic antioxidant molecules (reduced glutathione, superoxide dismutase, and glutathione peroxidase), compared to a control group, that more pronounced in the high dose of HDU. In addition, HDU induced significant upregulation of TNF-α and the Caspase-3 apoptotic pathway. Moreover, the liver of HDU treated groups showed various hepatic lesions from mild to severe necrotic changes related to the HDU dose. However, administration of RJ with HDU improved liver function tests, liver histology, and hepatic oxidative/antioxidative status concerning HDU groups. Furthermore, oral RJ administration with HDU significantly lessens the immune-expression area % of TNF-α and Caspase-3. Thus, the royal jelly has antioxidant, anti-inflammatory, and anti-apoptotic properties against HDU- induced hepatic injury and could be, therefore, used as adjuvant therapy in patients with long-term HDU medication.

Incorporation of 5-Bromo-2'-deoxyuridine into DNA and Proliferative Behavior of Cerebellar Neuroblasts: All That Glitters Is Not Gold

The synthetic halogenated pyrimidine analog, 5-bromo-2'-deoxyuridine (BrdU), is a marker of DNA synthesis. This exogenous nucleoside has generated important insights into the cellular mechanisms of the central nervous system development in a variety of animals including insects, birds, and mammals. Despite this, the detrimental effects of the incorporation of BrdU into DNA on proliferation and viability of different types of cells has been frequently neglected. This review will summarize and present the effects of a pulse of BrdU, at doses ranging from 25 to 300 µg/g, or repeated injections. The latter, following the method of the progressively delayed labeling comprehensive procedure. The prenatal and perinatal development of the cerebellum are studied. These current data have implications for the interpretation of the results obtained by this marker as an index of the generation, migration, and settled pattern of neurons in the developing central nervous system. Caution should be exercised when interpreting the results obtained using BrdU. This is particularly important when high or repeated doses of this agent are injected. I hope that this review sheds light on the effects of this toxic maker. It may be used as a reference for toxicologists and neurobiologists given the broad use of 5-bromo-2'-deoxyuridine to label dividing cells.

Administration of 5-bromo-2'-deoxyuridine interferes with neuroblast proliferation and promotes apoptotic cell death in the rat cerebellar neuroepithelium

The current study was conducted to assess whether a single administration of 5-bromo-2'-deoxyuridine (BrdU) interferes with cell proliferation and leads to the activation of apoptotic cellular events in the prenatal cerebellum. BrdU effects across a wide range of doses (25-300 μg/g b.w.) were analyzed using immunohistochemical and ultrastructural procedures. The pregnant rats were injected with BrdU at embryonic day 13, and their fetuses were sacrificed from 5 to 35 hr after exposure. The quantification of several parameters such as the density of mitotic figures, and BrdU and proliferating cell nuclear antigen (PCNA)-reactive cells showed that, in comparison with the saline injected rats, the administration of BrdU impairs the proliferative behavior of neuroepithelial cells. The above-mentioned parameters were significantly reduced in rats injected with 100 μg/g b.w. of BrdU. The reduction was more evident using 200 μg/g b.w. The most severe effects were found with 300 μg/g b.w. of BrdU. The present findings also revealed that high doses of BrdU lead to the activation of apoptotic cellular events as evidenced by both terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and immunohistochemistry for active caspase-3. In comparison with saline rats, many apoptotic cells were found in rats injected with 100 μg/g b.w. of BrdU. The number of dying cells increased with 200 μg/g b.w. The most important number of apoptotic cells were observed in animals injected with 300 μg/g b.w. of BrdU. Ultrastructural studies confirmed the presence of neuroblasts at different stages of apoptosis.

An immunocytochemical approach to the analysis of the cell division cycle in the rat cerebellar neuroepithelium

Cerebellar neurons are generated from the rhombic lip and the neuroepithelium. In this study, we analyze the histogenesis of the cerebellar neuroepithelium in terms of cellular kinetics. The experimental animals are the offspring of pregnant dams injected with 5-bromo-2'-deoxyuridine (BrdU) on embryonic day 13. We infer the fraction of S-phase cells by examining a range of survival times after a single BrdU-exposure and a cumulative BrdU-labeling sequence, which allow for the derivation of cell-cycle parameters and phase durations. The current results indicate that the dose of BrdU employed (35 mg/kg) provides saturation S-phase labeling from at least 1 h after marker delivery. The duration of G2, mitotic phase, and G1 are 1.2, 0.5, and 6.9 h, respectively. The duration for the S-phase, growth fraction, and the whole cycle are obtained on the basis of two proliferative models, steady-state and exponential growth. Both models provided similar results. In conclusion, our results indicate that the steady-state and the cumulative S-phase labeling paradigms can be adopted to analyze cell cycle parameters in the cerebellar neuroepithelium. Current results can help in understanding the regulatory mechanisms of cerebellar histogenesis and the cell biological mechanisms of the proliferative cycle of the neuroepithelium.

An Animal Model for Assessing the Effects of Hydroxyurea Exposure Suggests That the Administration of This Agent to Pregnant Women and Young Infants May Not Be as Safe as We Thought

The cytostatic agent hydroxyurea (HU) has proven to be beneficial for a variety of conditions in the disciplines of oncology, hematology, infectious disease and dermatology. It disrupts the S phase of the cell cycle by inhibiting the ribonucleotide reductase enzyme, thus blocking the transformation of ribonucleotides into deoxyribonucleotides, a rate limiting step in DNA synthesis. HU is listed as an essential medicine by the World Health Organization. Several studies have indicated that HU is well tolerated and safe in pregnant women and very young pediatric patients. To our knowledge, only a few controlled studies on the adverse effects of HU therapy have been done in humans. Despite this, the prevalence of central nervous system abnormalities, including ischemic lesions and stenosis have been reported. This review will summarize and present the effects of HU exposure on the prenatal and perinatal development of the rat cerebellar cortex and deep cerebellar nuclei neurons. Our results call for the necessity to better understand HU effects and define the administration of this drug to gestating women and young pediatric patients.