Nikola Zivkovic

Multiple sclerosis and glutamate excitotoxicity

Abstract The previous understanding of multiple sclerosis was solely related to neuroinflammation and its harmful effects; however, countless data indicate the importance of some inflammation-independent, neurodegenerative mechanisms associated with mitochondria malfunction, iron deposition and oxidative stress. Recently, it has been postulated that glutamate excitotoxicity, a phenomenon that takes place when an excessive amount of glutamate overactivates its cellular receptors and induces cell death, could be a missing link between inflammatory and neurodegenerative processes evident in multiple sclerosis. Glutamate is the major excitatory neurotransmitter of the central nervous system, which has been proven to have a central role in a complex communication network established between all residential brain cells, including neurons, astrocytes, oligodendrocytes and microglia. Thus, the disturbance of glutamate homeostasis could affect practically all physiological functions and interactions of brain cells, leading to heterogeneity of pathological events. The understanding of glutamate excitotoxicity as a valid mechanism of central nervous system damage in multiple sclerosis, requires the revision of the current knowledge about a source of elevated extracellular glutamate, glutamate receptor alterations, alterations of glutamate transporters and metabolizing enzymes, as well as molecular mechanism of excitotoxic damage.

IL-17 and glutamate excitotoxicity in the pathogenesis of multiple sclerosis.

Immunoinflammatory‐mediated demyelination, the main pathological feature of multiple sclerosis (MS), is regularly accompanied by neurodegenerative processes, mostly in the form of axonal degeneration, which could be initiated by glutamate excitotoxicity. In the current study, the relationship between Th17‐mediated inflammatory and excitotoxic events was investigated during an active phase of MS. Cerebrospinal fluid (CSF) of patients with MS and control subjects was collected, and IL‐17A and glutamate levels were determined. IL‐17A level was significantly higher in patients with MS; whereas no statistically significant changes in glutamate concentrations were found. There was a direct correlation between IL‐17A and glutamate levels; IL‐17A levels were also associated with the neutrophil expansion in CSF and blood–brain barrier disruption. However, IL‐17A level and the number of neutrophils tended to fall with disease duration. The results suggest that Th17 cells might enhance and use glutamate excitotoxicity as an effector mechanism in the MS pathogenesis. Furthermore, Th17 immune response, as well as neutrophils, could be more important for MS onset rather than further disease development and progression, what could explain why some MS clinical trials, targeting Th17 cells in the later stage of the disease, failed to provide any clinical benefit.

Deleterious versus protective autoimmunity in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disorder of central nervous system, in which myelin specific CD4(+) T cells have a central role in orchestrating pathological events involved in disease pathogenesis. There is compelling evidence that Th1, Th9 and Th17 cells, separately or in cooperation, could mediate deleterious autoimmune response in MS. However, the phenotype differences between Th cell subpopulations initially employed in MS pathogenesis are mainly reflected in the different patterns of inflammation introduction, which results in the development of characteristic pathological features (blood-brain barrier disruption, demyelination and neurodegeneration), clinically presented with MS symptoms. Although, autoimmunity was traditionally seen as deleterious, some studies indicated that autoimmunity mediated by Th2 cells and T regulatory cells could be protective by nature. The concept of protective autoimmunity in MS pathogenesis is still poorly understood, but could be of great importance in better understanding of MS immunology and therefore, creating better therapeutic strategies.

Blood Pressure Variability and Left Ventricular Mass Index in Children

Clinical implications of blood pressure variability (BPV) on subclinical organ damage in children are unknown. The authors sought to explore the potential utility of two newly derived BPV indices: weighted standard deviation (wBPSD) and real average variability (ARV), as well as two standard ambulatory blood pressure indices: average 24‐hour systolic blood pressure (SBP) and 24‐hour SBP load, to identify children at high risk for left ventricular (LV) hypertrophy (LVH). The study group consisted of 67 consecutive children who were referred to our institution for evaluation of suspected hypertension. LV mass was estimated by M‐mode echocardiography using Devereuxs formula according to the Penn convention and indexed for height2.7. We found a statistically significant, positive correlation between 24‐hour wBPSD and LV mass index (LVMI) (ρ=0.389; P=.002) and no correlation between 24‐hour ARV and LVMI (P>.05). However, partial correlation analysis of 24‐hour wBPSD adjusted for body mass index (BMI) and LVMI showed only a weak correlation (ρ=0.3; P=.022). By using multiple linear regression analysis in a model with LVMI as a dependent variable and 24‐hour wBPSD, 24‐hour ARV, and BMI as independent variables, only BMI showed statistically significant independent positive associations with LVMI (P=.028). Results of our study showed that currently used BPV indices (24‐hour wBPSD and 24‐hour ARV) are not clinically reliable parameters to identify children at risk for LVH. Apparent contribution of the 24‐hour wBPSD parameter to LVMI is negligible and is secondary to its close correlation with BMI (ρ=0.335 P=.009).

The therapeutic efficacy of propranolol in children with recurrent primary epistaxis

We hypothesized that some characteristics of beta-blockers, including negative inotropic, peripheral vasoconstrictor, and antiangiogenic effects, might be potentially useful in treating children with epistaxis. From June 2010 to March 2012, a total of seven children with recurrent primary epistaxis resistant to conventional management were observed at our institution. An overall effectiveness of propranolol was noted in all seven children when given a dose of 1.5–2 mg/kg/day (divided into three doses) as a second line therapy for terminating epistaxis. Based on our first experience, we believe that propranolol could be a favorable treatment option for patients with primary epistaxis.

Primary leptomeningeal melanocytosis--a case report with an autopsy diagnosis.

INTRODUCTION Primary melanocytosis of the leptomeninges is a rare tumor, most likely originating from the melanocytes in the leptomeninges. The average survival is only about 5 months. CASE REPORT A 61-years-old woman presented with headache, amaurosis and hallucinations lasted for two months, and she had been treated at the Clinic for Psychiatry and Clinic for Infectious Diseases. The cerebrospinal fluid analysis showed a lower level of glucose and a higher level of proteins. Small shaded areas of basal leptomeninges and hydrocephalus were found by computed tomography and magnetic resonance imaging. The autopsy showed a dark brown mass on basal leptomeninges with blurred boundaries. No pigmented skin lesions were found. Histopathological analysis revealed a primary leptomeningeal melanocytosis. CONCLUSION Primary leptomeningeal melanocytosis is a rare tumor, difficult to diagnose. This case is being presented for its specificity, since this diagnosis is not frequently seen in practice.

IL-17 signalling in astrocytes promotes glutamate excitotoxicity: Indications for the link between inflammatory and neurodegenerative events in multiple sclerosis

OBJECTIVE Th-17 cells have been exclusively referred to inflammatory events in multiple sclerosis (MS), while their importance in the development of glutamate excitotoxicity and the consequent neurodegeneration has been a completely unexplored concept. Accordingly, the objective of our study was to assess IL-17A effect on astrocyte ability to metabolize and release glutamate, considering that astrocytes had the central role in glutamate homeostasis. METHODS By using primary rat astrocyte cultures, astrocyte ability to uptake glutamate was estimated by the alterations of glutamate transporters (GLAST and GLT-1) expression, whereas changes in glutamine synthetase expression were used to estimate the ability to metabolize glutamate. Gene expression was determined by real time polymerase chain reaction (rtPCR). IL-17A effect on astrocyte ability to produce glutamate was investigated directly, by measuring the level of released glutamate using high performance liquid chromatography (HPLC). RESULTS Lower concentrations of IL-17A reduced the expressions of both glutamate transporters and glutamine synthetase; however, this effect was lost when IL-17A was applied in a higher dose. IL-17A did not significantly modify glutamate release from astrocyte in basal conditions, but following Ca2+ stimulation, as well as Ca2+ removal from the culture medium, IL-17A stimulated glutamate release in dose-dependent manner. CONCLUSION Together, these results support that IL-17A could promote glutamate excitotoxicity by decreasing astrocyte ability to uptake and convert glutamate to non-toxic glutamine, but also by stimulating Ca2+ dependent glutamate release. Such interactions between IL-17A and glutamate excitotoxicity implicate the potential link between inflammation and neurodegeneration during MS pathogenesis, and identify astrocytes as a potential target in achieving neuroprotective effects in MS.

A rare case of retroperitoneal malignant Triton tumor invading renal vein and small intestine.

INTRODUCTION Malignant Triton tumor is a very rare malignant peripheral nerve sheath tumor with rhabdomyosarcomatous differentiation. Most of those tumors occur in patients with von Recklinghausens disease or as a late complication of irradiation and commonly seen in the head, neck, extremities and trunk. CASE REPORT We reported retroperitoneal malignant Triton tumor in a 57-year-old female patient. Skin lesions were not present, and there was no family history of neurofibromatosis or previous irradiation. The presented case is one of a few recorded in the specialized literature that occurs in the retroperitoneal space in sporadic form. In this case, tumor consisted of a multilobular mass was in close relation with the abdominal aorta and inferior vena cava and involved the renal vein with gross invasion of the small intestine. The patient underwent total resection of the tumor and left nefrectomy was performed. The small intestine 10 cm in length was also resected and end-to-end anastomosis was conducted. The postoperative course was uneventful and the patient was discharged from the hospital ten days after the surgery. CONCLUSION Diagnostically, it is crucial to recognize this uncommon histological variant because malignant Triton tumor has a worse prognosis than classic malignant peripheral nerve sheath tumor does. The use of the immunohistochemistry is essential in making the correct diagnosis. Only appropriate pathological evaluation supported by immunostaining with S-100 protein and desmin confirmed the diagnosis. Aggressive surgical management treatment improves the prognosis of such cases with adjuvant radiotherapy.

Granulocyte-macrophage colony-stimulating factor as a mediator of autoimmunity in multiple sclerosis

Autoreactive, myelin-specific, CD4+ T cells have a central role in multiple sclerosis (MS) pathogenesis; however the exact phenotype characteristics of these cells remain elusive. Recently, granulocyte-macrophage colony-stimulating factor (GM-CSF) expression has emerged as the main pathological signature of the encephalogenicity in both T and B cell compartment. In this review we have summarized the current data supporting GM-CSF relevance in MS pathophysiology, in the context of both immunomodulatory and neuroinflammatory processes; as well as the potential cellular sources of this stimulating factor, including different T and B cell subsets.

Immunohistochemical and karyometric similarities and differences of salivary gland tumors between pleomorphic adenoma, basal cell adenoma and polymorphous low grade adenocarcinoma

Uvod: Tumori pljuvačnih žlezda su veoma retke neoplazme. S obzirom na njihovu patohistološku sliku, ovi tumori predstavljaju veoma veliki dijagnostički izazov. Cilj: istaživanja je diferencijacija ova tri tipa tumora primenom imunohistohemijske i morfometrijske analize, kao i određivanje visine Ki67 proliferativnog indeksa. Materijal i metode: Istraživanje je obuhvatilo 44 tumora, 20 pleomorfnih adenoma, 12 adenoma bazalnih ćelija i 12 polimorfnih adenokarcinoma niskog gradusa. Analizirana je ekspresija Ki67, p53 i HER-2 antigena, kao markera proliferacije. U sklopu diferencijalne dijagnostike, analizirana je ekspresija CEA, EMA, GFAP, p63, vimentina, CK14, α-SMA, S-100 protein i WT1 antigena. Morfometrijska analiza vršena je u softverskom paketu „ImageJ” verzija 1.43u. Rezultati: Neoplastične ćelije u pleomorfnom adenomu su pokazale jaku ekspresiju GFAP, p63, WT1, vimentin i S100. U grupi od dvanaest polimorfnih adenokarcinoma niskog gradusa prisutna je difuzna ekspresija CK14, S100, vimentin i EMA su bili apsolutno eksprimirani, dok je αSMA bio negativan. Adenom bazalnih ćelija pokazuje pozitivnost na S-100, CEA, p63 i vimentin. Analizom vrednosti proliferativnog Ki67 indeksa ustanovljena je statistički značajna razlika u grupi pleomorfnog adenoma, što se dovodi u vezu sa čestim recidiviranjem. Morfometrijskom analizom se uočavaju veće vrednosti u grupi polimorfnog adenokarcinoma niskog gradusa, ali su statistički značajne razlike nađene samo za Feretov dijametar i integrisanu optičku gustinu u odnosu na pleomorfni adenom (p<0,05). U grupi adenoma bazalnih ćelija tumorske ćelije su pokazale statistički veće vrednosti za integrisanu optičku gustinu u odnosu na pleomorfni adenom (p<0,001). Zaključak: Za diferencijalnu dijagnozu tumora pljuvačnih žlezda, pored osnovne mikromorfološke, neophodna je i imunohistohemijska i morfometrijska analiza.