Proteasome and Neuroprotective Effect of Hyperbaric Oxygen Preconditioning in Experimental Global Cerebral Ischemia in Rats.

OBJECTIVES: We investigated the involvement of the proteasome in the mechanism of preconditioning with hyperbaric oxygen (HBO-PC). METHODS: The experiments were performed on male Wistar rats subjected to a transient global cerebral ischemia of 5 min duration (2-vessel occlusion model) and preconditioned or not with HBO for 5 preceding days (1 h HBO at 2.5 atmosphere absolute [ATA] daily). In subgroups of preconditioned rats, the proteasome inhibitor MG132 was administered 30 min prior to each preconditioning session. Twenty-four hours and 7 days post-ischemia, after neurobehavioral assessment, the brains were collected and evaluated for morphological changes and quantitative immunohistochemistry of cell markers and apoptosis-related proteins. RESULTS: We observed reduced damage of CA1 pyramidal cells in the HBO preconditioned group only at 7 days post-ischemia. However, both at early (24 h) and later (7 days) time points, HBO-PC enhanced the tissue expression of 20S core particle of the proteasome and of the nestin, diminished astroglial reactivity, and reduced p53, rabbit anti-p53 upregulated modulator of apoptosis (PUMA), and rabbit anti-B cell lymphoma-2 interacting mediator of cell death (Bim) expressions in the hippocampus and cerebral cortex. HBO-PC also improved T-maze performance at 7 days. Proteasome inhibitor abolished the beneficial effects of HBO-PC on post-ischemic neuronal injury and functional impairment and reduced the ischemic alterations in the expression of investigated proteins. SIGNIFICANCE: Preconditioning with hyperbaric oxygen-induced brain protection against severe ischemic brain insult appears to involve the proteasome, which can be linked to a depletion of apoptotic proteins and improved regenerative potential.

Inhibiting CK2 among Promising Therapeutic Strategies for Gliomas and Several Other Neoplasms.

In gliomas, casein kinase 2 (CK2) plays a dominant role in cell survival and tumour invasiveness and is upregulated in many brain tumours. Among CK2 inhibitors, benzimidazole and isothiourea derivatives hold a dominant position. While targeting glioma tumour cells, they show limited toxicity towards normal cells. Research in recent years has shown that these compounds can be suitable as components of combined therapies with hyperbaric oxygenation. Such a combination increases the susceptibility of glioma tumour cells to cell death via apoptosis. Moreover, researchers planning on using any other antiglioma investigational pharmaceutics may want to consider using these agents in combination with CK2 inhibitors. However, different compounds are not equally effective when in such combination. More research is needed to elucidate the mechanism of treatment and optimize the treatment regimen. In addition, the role of CK2 in gliomagenesis and maintenance seems to have been challenged recently, as some compounds structurally similar to CK2 inhibitors do not inhibit CK2 while still being effective at reducing glioma viability and invasion. Furthermore, some newly developed inhibitors specific for CK2 do not appear to have strong anticancer properties. Further experimental and clinical studies of these inhibitors and combined therapies are warranted.

Harnessing oxidative stress for anti-glioma therapy.

Glioma cells use intermediate levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) for growth and invasion, and suppressing these reactive molecules thus may compromise processes that are vital for glioma survival. Increased oxidative stress has been identified in glioma cells, in particular in glioma stem-like cells. Studies have shown that these cells harbor potent antioxidant defenses, although endogenous protection against nitrosative stress remains understudied. The enhancement of oxidative or nitrosative stress offers a potential target for triggering glioma cell death, but whether oxidative and nitrosative stresses can be combined for therapeutic effects requires further research. The optimal approach of harnessing oxidative stress for anti-glioma therapy should include the induction of free radical-induced oxidative damage and the suppression of antioxidant defense mechanisms selectively in glioma cells. However, selective induction of oxidative/nitrosative stress in glioma cells remains a therapeutic challenge, and research into selective drug delivery systems is ongoing. Because of multifactorial mechanisms of glioma growth, progression, and invasion, prospective oncological therapies may include not only therapeutic oxidative/nitrosative stress but also inhibition of oncogenic kinases, antioxidant molecules, and programmed cell death mediators.

Targeting protein kinases for anti-glioma treatment.

The genetic alterations related to many kinases are responsible for the formation of glial tumours. In addition it is the cell kinases that keep the cancerous signalling machinery in motion, thus enabling tumour cell growth, motility and invasion. Kinase inhibitors may have a potential to surpass the classical oncolytic treatment for gliomas. However, overcoming drug resistance mechanisms and limited blood-brain barrier (BBB) permeability are the remaining daunting issues. Latest research explores novel kinase inhibitors, yielding several promising results, including those from CK2 inhibition studies, as well as the possibility of relabelling the inhibitors previously approved for tumours other than glial tumours.

Novel small molecule protein kinase CK2 inhibitors exert potent antitumor effects on T98G and SEGA cells in vitro.

Tumours of astroglial origin, both malignant glioblastoma (GBM) and benign subependymal giant cell astrocytoma (SEGA), pose a serious medical problem. Casein kinase 2 (CK2), a member of the serine/threonine kinase family, has antiapoptotic properties and plays a vital role in glial tumour cell survival. It contributes to invasive cell growth and is often upregulated in malignant neoplastic cells; however, its role in benign tumours of astrocytic origin is less understood. In the present study we investigated the effects of small molecule CK2 inhibitors on proliferation and viability of glioma cells in vitro. The experiments were conducted on commercial T98G malignant glioma cell line and the SEGA cell line, derived from a paediatric case of tuberous sclerosis complex (TSC). Cell cultures were incubated with selected CK2 inhibitors: 4,5,6,7-tetrabromo-1H-benzimidazole (TBI), 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole (DMAT) and 4,5,6,7-tetrabromo-1H-benzotriazole (TBB) at 0.1, 1, 10, 25, 50, 75 and 100 µM concentrations for 24 and 48 hours. Cell proliferation was assessed using a cell counter and cell viability was evaluated by MTT assay. TBB at 75 µM and 100 µM, and TBI starting from 25 µM, both reduced T98G cell proliferation after 24 hours, while DMAT was ineffective. All tested small molecule CK2 inhibitors appear to reduce T98G cell growth and viability after 48 hours, although TBI appeared to be the most effective and reduced cell growth in the 50-100 µM dose range. TBI also showed potential efficacy in reducing the number and viability of SEGA cells after 48 hours. Proliferation and viability of SEGA cells have proven resistant to TBB treatment. DMAT only reduced the viability of SEGA cells at 24 (at 100 µM) and 48 hours (10-100 µM). Importantly, normal human astrocyte cells were found to be moderately resistant to TBB, while their viability was mildly reduced at higher doses of DMAT and TBI. In conclusion, CK2 appears to play a role not only in malignant glioma cells but it can also sustain the viability and proliferation of benign astrocytoma cells. The obtained antitumor effects of CK2 inhibitors significantly exceeded their mild or no effect on normal astrocytes in control, which supports the therapeutic potential of these compounds against gliomas.

Potent Antitumour Effects of Novel Pentabromobenzylisothioureas Studied on Human Glial-derived Tumour Cell Lines.

BACKGROUND/AIM: Tumours of astroglial origin are the most common primary brain malignancy characterized by infiltrative growth and resistance to standard antitumour therapy. Glioma progression is thought to be related to various intracellular signal transduction pathways that involve the activation of protein kinases. Protein kinases play important roles in cell differentiation, proliferation, and survival. Recently, novel, specific inhibitors of constitutively active serine/threonine kinases and structurally similar isothiourea derivatives were suggested to induce apoptosis and inhibit proliferation in several types of human cancer cells. MATERIALS AND METHODS: In this study, we examined the cytotoxic and proapoptotic activities of selected modified pentabromobenzyl isothioureas (ZKKs) in an adult human glioblastoma (T98G) and a subependymal giant cell astrocytoma cell (SEGA) line. We evaluated cell proliferation, viability, and apoptosis. RESULTS: Two pentabromobenzyl isothiourea bromide derivatives, ZKK-13 and N,N,N'-trimethyl-ZKK1 (TRIM), exhibited the most potent cytotoxic and proapoptotic efficacies against human glioma-derived cells, even at a very low concentration (1 µM). ZKK-13 (25-50 µM) inhibited cell growth by approximately 80-90% in 24 and 48 h of treatment. We showed that selected ZKKs exerted antiproliferative activity against astroglial neoplastic cells of both low- and high-grade tumour malignancy classes. No synergistic effects were detected when ZKKs were combined with serine/threonine kinase inhibitors. CONCLUSION: Our findings indicated that modified ZKKs show promise for the treatment of glioma-derived brain tumours.

The efficacy of hyperbaric oxygen in hemorrhagic stroke: experimental and clinical implications.

Hemorrhagic stroke, accounting for 10-30% of stroke cases, carries high rates of morbidity and mortality. This review presents the current knowledge on the efficacy of hyperbaric oxygen (HBO)-based modalities in the preclinical research on hemorrhagic stroke. Both preconditioning and post-treatment with HBO are considered as prospective therapeutic options. High efficacy of HBO therapy (HBOT) for brain hemorrhage has been noted. We found that moderate hyperbaric pressures appear optimal for therapeutic effect, while the therapeutic window of opportunity is short. HBO preconditioning offers more modest neuroprotective benefit as compared to HBO post-treatment for experimental intracerebral hemorrhage. We advocate for mandatory calculations of percent changes in the experimentally investigated indexes of HBO effectiveness and stress the need to design new clinical trials on HBO for hemorrhagic stroke.

Hyperbaric oxygen modalities are differentially effective in distinct brain ischemia models.

The effectiveness and efficacy of hyperbaric oxygen (HBO) preconditioning and post-treatment modalities have been demonstrated in experimental models of ischemic cerebrovascular diseases, including global brain ischemia, transient focal and permanent focal cerebral ischemia, and experimental neonatal hypoxia-ischemia encephalopathy. In general, early and repetitive post-treatment of HBO appears to create enhanced protection against brain ischemia whereas delayed HBO treatment after transient focal ischemia may even aggravate brain injury. This review advocates the level of injury reduction upon HBO as an important component for translational evaluation of HBO based treatment modalities. The combined preconditioning and HBO post-treatment that would provide synergistic effects is also worth considering.

Papillary glioneuronal tumor with an unusual bilateral intraventricular localization.

Papillary glioneuronal tumor (PGNT) is a rare brain tumor (World Health Organization grade I) with a glioneuronal dual nature. It has a characteristic morphological pattern composed of astroglial pseudopapillary structures and interpapillary neurocytic elements. The tumor usually occurs in the supratentorial region in children and young adults, with a predilection for the temporal lobe. It is typically localized within the deep white matter adjacent to the lateral ventricles and rarely invades the ventricular cavities. Predominantly intraventricular localization of PGNT is uncommon. We report our experience with a PGNT that was bilaterally localized within the lateral ventricles of a 27-year-old woman. Magnetic resonance imaging demonstrated a solid, partially cystic mass in the left and right lateral ventricles. Part of the tumor was removed by surgery, followed by radiation therapy. Histopathological studies revealed typical pseudopapillary structures, created by glial fibrillary acidic protein (GFAP)-immunopositive cells, arranged around hyalinized blood vessels. The interpapillary component was composed of small, uniform, neurocyte-like cells with strong synaptophysin reactivity. Mitoses were rare, and necrosis was absent. The MIB-1 labeling index was low. The tumor was diagnosed as a PGNT. To our knowledge, this is the only report of this rare entity being located bilaterally in both cavities of the lateral ventricles.

The coexistence of pleomorphic xanthoastrocytoma and arteriovenous malformation. A case report.

Pleomorphic xanthoastrocytoma (PXA) is a rare, low-grade astrocytic tumour corresponding to WHO grade II that is usually diagnosed in adolescents and young adults with epileptic seizures. Pleomorphic xanthoastrocytoma typically appears as a superficial, often cystic mass lesion predominantly affecting the temporal lobe. Cases with typical pathology and total tumour excision have a favourable prognosis. Occasionally, the tumour reveals anaplastic features and behaves more aggressively due to local recurrences or subarachnoid spread. The treatment of PXA includes gross total resection followed by neuroradiological monitoring. The association between vascular malformations and cerebral gliomas is rarely encountered, especially if both such lesions occur as separate parts of the same tumour. The vascular pathology of such changes most often refers to arteriovenous malformation (AVM), less frequently - cavernous angioma. The coexistence of PXA and AVM is extremely rare, especially when dealing with two distinct patterns found within the same tumour mass. We present a 36-year-old woman with tumour of parasagittal localization in the right occipital lobe that was composed of two different and clearly demarcated components: PXA and vascular lesion of AVM morphology. The pathogenesis of such coexistence remains still unclear.

Research of medical gases in Poland.

Research of medical gases is well established in Poland and has been marked with the foundation of several professional societies. Numerous academic centers including those dealing with hyperbaric and diving medicine conduct studies of medical gases, in vast majority supported with intramural funds. In general, Polish research of medical gases is very much clinical in nature, covering new applications and safety of medical gases in medicine; on the other hand there are several academic centers pursuing preclinical studies, and elaborating basic theories of gas physiology and mathematical modeling of gas exchange. What dominates is research dealing with oxygen and ozone as well as studies of anesthetic gases and their applications. Finally, several research directions involving noble gas, hydrogen and hydrogen sulfide for cell protection, only begin to gain recognition of basic scientists and clinicians. However, further developments require more monetary spending on research and clinical testing as well as formation of new collective bodies for coordinating efforts in this matter.