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Recently research shows that horseradish peroxidase, HRP, when combined with other compounds, is highly reactive toward different human tumour cells and that better understanding of catalytic mechanism and inhibition HPR could lead to a new targeted cancer therapy. Thus, the inhibition of HRP activity by dipotassium-trioxohydroxytetrafluorotriborate K2[B3O3F4OH] was investigated for possible explanation of previously observed antitumour activities of this promising drug. HRP activity was studied under steady-state kinetic conditions by a spectrophotometric method. In the absence of the inhibitor values of = 0.47 mM and = 0.34 mM min−1, respectively, were determined. The hydrogen peroxide H2O2 kinetic measurements show a competitive inhibition with the inhibition constant = 2.56 mM. The activation energy values were found to be very similar for both reactions; in the absence of inhibitor activation energy was 17.7 kJ mol−1 and in the presence of inhibitor activation energy was 16.3 kJ mol−1. The values of Arrhenius constants were found to be different; = 4.635 s−1 was measured in the absence of inhibitor while in the presence of inhibitor Arrhenius constant was 1.745 s−1 showing that K2[B3O3F4OH] initiates conformational change in the structure of the HRP and subsequently reduces its activity.

S. Ostojić, J. Ostojić, P. Drid, M. Vraneš

In this randomized, double-blind, crossover trial, we evaluated whether 4-week supplementation with guanidinoacetic acid (GAA) is superior to creatine in facilitating creatine levels in healthy men (n = 5). GAA (3.0 g/day) resulted in a more powerful rise (up to 16.2%) in tissue creatine levels in vastus medialis muscle, middle-cerebellar peduncle, and paracentral grey matter, as compared with creatine (P < 0.05). These results indicate that GAA as a preferred alternative to creatine for improved bioenergetics in energy-demanding tissues.

J. Ostojić, C. Panozzo, A. Bourand-Plantefol, C. J. Herbert, G. Dujardin, N. Bonnefoy

Mitochondria have their own translation machinery that produces key subunits of the OXPHOS complexes. This machinery relies on the coordinated action of nuclear-encoded factors of bacterial origin that are well conserved between humans and yeast. In humans, mutations in these factors can cause diseases; in yeast, mutations abolishing mitochondrial translation destabilize the mitochondrial DNA. We show that when the mitochondrial genome contains no introns, the loss of the yeast factors Mif3 and Rrf1 involved in ribosome recycling neither blocks translation nor destabilizes mitochondrial DNA. Rather, the absence of these factors increases the synthesis of the mitochondrially-encoded subunits Cox1, Cytb and Atp9, while strongly impairing the assembly of OXPHOS complexes IV and V. We further show that in the absence of Rrf1, the COX1 specific translation activator Mss51 accumulates in low molecular weight forms, thought to be the source of the translationally-active form, explaining the increased synthesis of Cox1. We propose that Rrf1 takes part in the coordination between translation and OXPHOS assembly in yeast mitochondria. These interactions between general and specific translation factors might reveal an evolutionary adaptation of the bacterial translation machinery to the set of integral membrane proteins that are translated within mitochondria.

S. Ostojić, P. Drid, J. Ostojić, J. Hoffman

The accumulation of reactive free radicals will lead to oxidative stress which can cause oxidative damage to bimolecular such as protein, lipid, and DNA. It also can induce injury to tissues or organs and is one of the reasons for fatigue. Therefore, supplementing with antioxidants has been considered to have an important role in reducing the degree of fatigue caused by free radical and oxidative stress. PURPOSE: Glutathione (GSH) possesses a significant antioxidant effect and reduces oxidative stress. However, GSH like other natural anti-oxidants is limited by poor stability, short half-life in vivo, low bioavailability, and is easily degraded by proteolytic or gastrointestinal enzymes. Therefore, using nanomaterials as an efficient delivery system for antioxidants can solve these problems and improve clinical therapy. METHODS: Glutathione (GSH) antioxidants were successfully intercalated into layered double hydroxides (LDH) nanoparticles and characterized by X-ray powder diffraction and transmission electron microscopy. The in vitro cytotoxicity assays was studied by MTT test. The in vivo anti-fatigue effect was examined by animal assay. Sixty mice were randomly divided into six groups with ten mice each: two control groups, two GSH treatment groups and two GSH-LDH treatment groups. The forced swimming test was conducted on the last day and corresponding biochemical parameters were measured. RESULTS: The in vitro cytotoxicity assays indicated that GSH-LDH antioxidant system had no significant cytotoxic effect or obvious toxicity to normal cells. It also prolonged the forced swimming time of the mice by 25% and 41% compared to GSH and control groups, respectively. It had an obvious effect on decreasing the blood urea nitrogen and blood lactic acid, while increasing muscle and hepatic glycogen levels. CONCLUSION: GSH-LDH might be used as a novel antioxidant and anti-fatigue sports nutritional supplement. Future work will focus on the study of antioxidant and antifatigue mechanisms at the molecular level. This work was financially supported by the National Natural Science Foundation of China (Grant No 31100855, 31401019)

D. Kust, I. Kruljac, Ana Šverko Peternac, J. Ostojić, M. Prpić, D. Čaržavec, P. Gaćina

To best of our knowledge, this is the first reported case of pericardial and pleural effusions combined with ascites, precipitated with severe sunitinib-induced hypothyroidism. A 58-year-old man presented in our emergency department due to dyspnoea and dry cough. Sixteen months earlier, the patient underwent left nephrectomy due to metastatic renal cell adenocarcinoma (RCC), and therapy with sunitinib was initiated postoperatively. Thyroid function was not assessed during the therapy. On admission, all laboratory findings were within normal range. Computed tomography of the chest detected voluminous bilateral pleural effusions and mild pericardial effusion, and echocardiography revealed pericardial effusion. Thoracocentesis was carried out three times, and cytological examination showed no signs of malignant cells. After assessment of the thyroid function, neglected hypothyroidism was registered. Substitution therapy with levothyroxine was initiated, and thyroid function normalised 2 weeks later. Few days after the last thoracocentesis, his condition suddenly got worse. Thoracocentesis was repeated, and microbiological analysis of the exudate came positive for Klebsiella pneumoniae and Streptococcus pneumoniae. Despite the implemented therapeutic measures, his clinical condition progressively deteriorated. The patient died 27 days after the admission, hospital-acquired pneumonia was identified as the cause of death. Our case emphasises the necessity of careful monitoring and management of side-effects in patients who receive sunitinib. Hypothyroidism is a known cause of pleural, pericardial and abdominal effusions, as reported in several case reports. Timely initiation of substitution levothyroxine therapy can decrease unnecessary pauses in the therapy with sunitinib, as well as prevent development of severe symptoms.

P. Perić, G. Pavlićević, J. Ostojić, D. Kostić, Sanja Nikolajević, G. Šupić, Z. Magic, Sanja Radovinović-Tasić

Introduction. Synchronous multicentric cerebral gliomas are uncommon brain tumors, mostly malignant, with unknown pathogenesis, unfavorable prognosis and still controversial management. Preoperative differentiation from other multiple brain pathologies by conventional magnetic resonance imaging (MRI) is often difficult, but supplemental use of advanced magnetic resonance techniques should allow the tumor biology to be predicted, and an appropriate treatment strategy planned. Case report. We report the case of a 59-year-old man with double synchronous multicentric cerebral lesions, which had initial MRI and diffusion-weighted imaging presentation as left parietal metastasis and ipsilateral amygdalo-hippocampal low-grade glioma. However, magnetic resonance spectroscopy (MRS) of both lesions showed different metabolite profiles of malignant glioma. En bloc resection of the easily accessible parietal lesion revealed glioblastoma with methylated O6-methylguanine-DNA methyltransferase (MGMT) gene promoter. Subsequently, the patient was treated with temozolomide (TMZ)-based chemoradiation according to Stupp’s protocol, with continuous standard (5/28) adjuvant TMZ in 12 courses. Despite prolonged stabilization of the disease with good life-quality during treatment, the patient died 19 months after diagnosis. The time to tumor progression estimated by MRI was 17 months. Conclusion. MRS significantly improved the differential diagnostic accuracy of conventional MRI in our patient. In accordance with reviewed literature data, the younger age, good initial performance status and methylated MGMT gene promoter were all favorable predictors of longer survival in the reported case. Resection of at least one easily accessible tumor lesion, followed by TMZ-based chemoradiation, with continuous adjuvant TMZ in more than 6 standard courses, seems currently to be the most beneficial therapeutic option for such cases.

J. Jančić, I. Dejanović, S. Radovanovic, J. Ostojić, D. Kozic, M. Đurić-Jovičić, J. Samardžić, M. Ćetković et al.

We are presenting two Leber's hereditary optic neuropathy (LHON) pedigrees with abnormal magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (H-MRS) findings but without neurological manifestation associated with LHON. The study included 14 LHON patients and 41 asymptomatic family members from 12 genealogically unrelated families. MRI showed white matter involvement and H-MRS exhibited metabolic anomalies within 12 LHON families. Main outcome measures were abnormal MRI and H-MRS findings in two pedigrees. MRI of the proband of the first pedigree showed a single demyelinating lesion in the right cerebellar hemisphere, while the proband of the second family displayed multiple supratentorial and infratentorial lesions, compatible with the demyelinating process, and both the absolute choline (Cho) concentration and Cho/creatinine ratio were increased. MRI and H-MRS profiles of both affected and unaffected mitochondrial DNA mutation carriers suggest more widespread central nervous involvement in LHON. Although even after 12 years our patients did not develop neurological symptoms, MRI could still be used to detect possible changes during the disease progression.

S. Ivanković, R. Stojković, Z. Galic, B. Galić, J. Ostojić, Maja Marasović, M. Miloš

Abstract Dipotassium-trioxohydroxytetrafluorotriborate K2[B3O3F4OH] was listed as a promising new therapeutic for cancer diseases. For in vitro and in vivo investigation of its antitumor effects 4T1 mammary adenocarcinoma, B16F10 melanoma and squamous cell carcinoma SCCVII were used. The detailed in vitro investigation undoubtedly showed that K2[B3O3F4OH] affects the growth of cancer cells. The proliferation of cells depends on the concentration so that aqueous solution of K2[B3O3F4OH], the concentrations of 10−4 M and less, does not affect cell growth, but the concentrations of 10−3 M or more, significantly slows cells growth. B16F10 and SCCVII cells show higher sensitivity to the cytotoxic effects of K2[B3O3F4OH] compared to 4T1 cells. Under in vivo conditions, K2[B3O3F4OH] slows the growth of all three tumors tested compared to the control, and the inhibitory effect was most pronounced during the application of the substance. There is almost no difference if K2[B3O3F4OH] was applied intraperitoneally, intratumor, peroral or as ointment. Addition of 5-FU did not further increase the antitumor efficacy of K2[B3O3F4OH].

A. Potic, V. Popović, J. Ostojić, S. Pekic, D. Kozic, K. Guerrero, R. Schiffmann, G. Bernard

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