Oxidative Stress in the Brain: Basic Concepts and Treatment Strategies in Stroke

The production of free radicals is inevitably associated with metabolism and other enzymatic processes. Under physiological conditions, however, free radicals are effectively eliminated by numerous antioxidant mechanisms. Oxidative stress occurs due to an imbalance between the production and elimination of free radicals under pathological conditions. Oxidative stress is also associated with ageing. The brain is prone to oxidative damage because of its high metabolic activity and high vulnerability to ischemic damage. Oxidative stress, thus, plays a major role in the pathophysiology of both acute and chronic pathologies in the brain, such as stroke, traumatic brain injury or neurodegenerative diseases. The goal of this article is to summarize the basic concepts of oxidative stress and its significance in brain pathologies, as well as to discuss treatment strategies for dealing with oxidative stress in stroke.

Uncovering Active Bacterial Symbionts in Pollen-Feeding Beetles

Microbial symbionts enable many phytophagous insects to specialize on plant-based diets through a range of metabolic services. Pollen comprises one plant tissue consumed by such herbivores. While rich in lipids and protein, its nutrient content is often imbalanced and difficult-to-access due to a digestibly recalcitrant cell wall. Pollen quality can be further degraded by harmful allelochemicals. To identify microbes that may aid in palynivory, we performed cDNA-based 16S rRNA metabarcoding on three related pollen beetles (Nitidulidae: Meligethinae) exhibiting different dietary breadths: Brassicogethes aeneus, B. matronalis, and Meligethes atratus. Nine bacterial symbionts (i.e. 97% OTUs) exhibited high metabolic activity during active feeding. Subsequent PCR surveys revealed varying prevalence of those from three Rickettsialles genera - Lariskella, Rickettsia and Wolbachia - within beetle populations. Our findings lay the groundwork for future studies on the influence of phylogeny and diet on palynivorous insect microbiomes, and roles of symbionts in the use of challenging diets.

Use of Propionibacterium freudenreichii T82 Strain for Effective Biosynthesis of Propionic Acid and Trehalose in a Medium with Apple Pomace Extract and Potato Wastewater

Propionic acid bacteria are the source of many metabolites, e.g., propionic acid and trehalose. Compared to microbiological synthesis, the production of these metabolites by petrochemical means or enzymatic conversion is more profitable. The components of microbiological media account for a large part of the costs associated with propionic fermentation, due to the high nutritional requirements of Propionibacterium. This problem can be overcome by formulating a medium based on the by-products of technological processes, which can act as nutritional sources and at the same time replace expensive laboratory preparations (e.g., peptone and yeast extract). The metabolic activity of P. freudenreichii was investigated in two different breeding environments: in a medium containing peptone, yeast extract, and biotin, and in a waste-based medium consisting of only apple pomace and potato wastewater. The highest production of propionic acid amounting to 14.54 g/L was obtained in the medium containing apple pomace and pure laboratory supplements with a yield of 0.44 g/g. Importantly, the acid production parameters in the waste medium reached almost the same level (12.71 g/L, 0.42 g/g) as the medium containing pure supplements. Acetic acid synthesis was more efficient in the waste medium; it was also characterized by a higher level of accumulated trehalose (59.8 mg/g d.s.). Thus, the obtained results show that P. freudenreichii bacteria exhibited relatively high metabolic activity in an environment with apple pomace used as a carbon source and potato wastewater used as a nitrogen source. This method of propioniate production could be cheaper and more sustainable than the chemical manner.

The Concept of Folic Acid in Health and Disease

Folates have a pterine core structure and high metabolic activity due to their ability to accept electrons and react with O-, S-, N-, C-bounds. Folates play a role as cofactors in essential one-carbon pathways donating methyl-groups to choline phospholipids, creatine, epinephrine, DNA. Compounds similar to folates are ubiquitous and have been found in different animals, plants, and microorganisms. Folates enter the body from the diet and are also synthesized by intestinal bacteria with consequent adsorption from the colon. Three types of folate and antifolate cellular transporters have been found, differing in tissue localization, substrate affinity, type of transferring, and optimal pH for function. Laboratory criteria of folate deficiency are accepted by WHO. Severe folate deficiencies, manifesting in early life, are seen in hereditary folate malabsorption and cerebral folate deficiency. Acquired folate deficiency is quite common and is associated with poor diet and malabsorption, alcohol consumption, obesity, and kidney failure. Given the observational data that folates have a protective effect against neural tube defects, ischemic events, and cancer, food folic acid fortification was introduced in many countries. However, high physiological folate concentrations and folate overload may increase the risk of impaired brain development in embryogenesis and possess a growth advantage for precancerous altered cells.

Prognostic relevance of the hexosamine biosynthesis pathway activation in leiomyosarcoma

Metabolic reprogramming of tumor cells and the increase of glucose uptake is one of the hallmarks of cancer. In order to identify metabolic pathways activated in leiomyosarcoma (LMS), we analyzed transcriptomic profiles of distinct subtypes of LMS in several datasets. Primary, recurrent and metastatic tumors in the subtype 2 of LMS showed consistent enrichment of genes involved in hexosamine biosynthesis pathway (HBP). We demonstrated that glutamine-fructose-6-phosphate transaminase 2 (GFPT2), the rate-limiting enzyme in HBP, is expressed on protein level in a subset of LMS and the expression of this enzyme is frequently retained in patient-matched primary and metastatic tumors. In a new independent cohort of 327 patients, we showed that GFPT2 is associated with poor outcome of uterine LMS but not extra-uterine LMS. Based on the analysis of a small group of patients studied by 18F-FDG-PET imaging, we propose that strong expression of GFPT2 in primary LMS may be associated with high metabolic activity. Our data suggest that HBP is a potential new therapeutic target in one of the subtypes of LMS.

Cullin-5 neddylation-mediated NOXA degradation is enhanced by PRDX1 oligomers in colorectal cancer

NOXA, a BH3-only proapoptotic protein involved in regulating cell death decisions, is highly expressed but short-lived in colorectal cancer (CRC). Neddylated cullin-5 (CUL5)-mediated ubiquitination and degradation of NOXA is crucial to prevent its overaccumulation and maintain an appropriate action time. However, how this process is manipulated by CRC cells commonly exposed to oxidative stress remain unknown. The peroxiredoxin PRDX1, a conceivable antioxidant overexpressed in CRC tissues, has been shown to inhibit apoptosis and TRAF6 ubiquitin-ligase activity. In this study, we found that PRDX1 inhibits CRC cell apoptosis by downregulating NOXA. Mechanistically, PRDX1 promotes NOXA ubiquitination and degradation, which completely depend on CUL5 neddylation. Further studies have demonstrated that PRDX1 oligomers bind with both the Nedd8-conjugating enzyme UBE2F and CUL5 and that this tricomplex is critical for CUL5 neddylation, since silencing PRDX1 or inhibiting PRDX1 oligomerization greatly dampens CUL5 neddylation and NOXA degradation. An increase in reactive oxygen species (ROS) is not only a hallmark of cancer cells but also the leading driving force for PRDX1 oligomerization. As shown in our study, although ROS play a role in upregulating NOXA mRNA transcription, ROS scavenging in CRC cells by N-acetyl-L-cysteine (NAC) can significantly reduce CUL5 neddylation and extend the NOXA protein half-life. Therefore, in CRC, PRDX1 plays a key role in maintaining intracellular homeostasis under conditions of high metabolic activity by reinforcing UBE2F-CUL5-mediated degradation of NOXA, which is also evidenced in the resistance of CRC cells to etoposide treatment. Based on these findings, targeting PRDX1 could be an effective strategy to overcome the resistance of CRC to DNA damage-inducing chemotherapeutics.

Imaging features of fumarate hydratase-deficient renal cell carcinomas: a retrospective study

Backgound Fumarate hydratase-deficient renal cell carcinoma (FH-RCC) is a subtype of RCC that is increasingly recognized pathologically. The aim of this study was to evaluate the imaging features of FH-RCC on computed tomography (CT), magnetic resonance imaging (MRI), and fluorodeoxyglucose positron emission tomography (FDG PET), and to determine the pre-operative diagnostic potential of imaging. Methods This single-site retrospective study included patients with histologically confirmed FH-RCC or with a renal cancer and known germline FH mutation; imaging of the renal mass before treatment with contrast-enhanced CT, contrast-enhanced MRI, or FDG PET/CT between October 2007 and May 2019. Clinical information, pathological data, and imaging features were analyzed and reported descriptively. Results Sixteen patients with sixteen tumors were included (median age 46 years, interquartile range 38–53 years; 31 % female). Almost all tumors were unifocal (15/16, 94 %). Most tumors had infiltrative margins (14/16, 88 %); few were circumscribed (2/16, 12 %). A large cystic tumor component (> 75 % of tumor volume) was seen in 8/16 (50 %) of tumors. Involvement of renal sinus fat was seen in 13/16 (81 %) of tumors, involvement of the hilar collecting system in 8/16 (50 %), and renal vein tumor thrombus in 6/16 (38 %). All 12 tumors (100 %) imaged with MRI had heterogenous tumor enhancement and heterogenous T2 signal. Of those patients that had diffusion-weighted imaging, 11/11 (100 %) of tumors had diffusion restriction in the solid portions of the tumor. Of the patients who had PET, 3/3 (100 %) tumors showed high metabolic activity with mean maximum standardized uptake value (SUVmax) of 16.4 (range 9.6–21.9). Patients presented with retroperitoneal nodal metastases in 69 % of cases and distant metastases in 75 %. Of those four patients without metastatic disease at presentation, three (75 %) developed metastases within 4 years of diagnosis. Conclusions In our study, the majority of tumors (≥ 75 %) were unifocal, had an infiltrative margin, invaded the renal sinus fat, and presented with distant metastases. On MRI, most tumors had heterogenous T2 signal and diffusion restriction in their solid components. The small number of cases that had PET imaging showed high metabolic activity.

Diploid hepatocytes drive physiological liver renewal in adult humans

SummaryPhysiological liver cell replacement is central to maintaining the organ’s high metabolic activity, although its characteristics are difficult to study in humans. Using retrospective 14C birth dating of cells, we report that human hepatocytes show continuous and lifelong turnover, maintaining the liver a young organ (average age < 3 years). Hepatocyte renewal is highly dependent on the ploidy level. Diploid hepatocytes show an seven-fold higher annual exchange rate than polyploid hepatocytes. These observations support the view that physiological liver cell renewal in humans is mainly dependent on diploid hepatocytes, whereas polyploid cells are compromised in their ability to divide. Moreover, cellular transitions between these two subpopulations are limited, with minimal contribution to the respective other ploidy class under homeostatic conditions. With these findings, we present a new integrated model of homeostatic liver cell generation in humans that provides fundamental insights into liver cell turnover dynamics.

FRI0214 PERSISTENT LOW-GRADE FDG-PET VASCULAR INFLAMMATION IN REMITTED LVV-GCA PATIENTS IS ASSOCIATED TO A SIGNIFICANT HIGH RISK OF RELAPSE

Background:Persistent low-grade vascular inflammation in giant cell arteritis (GCA) with large vessel involvement (LVV) treated patients could represent the expression of persistent subclinical disease activity or post-inflammatory vascular remodelling. Whether these findings have any impact on future vascular outcomes is still an unmet need.Objectives:To evaluate the frequency and evolution of FDG-PET low-grade vascular inflammation in remitted LVV-GCA patients.Methods:We included all consecutive patients classified as GCA with LVV involvement, with a minimum disease duration of 12 months and clinically remitted, who underwent to at least one PET/MR scan between January 2015 and January 2020. For each scan vessel’s metabolic activity was assessed using the Meller’s grading1. Low-grade inflammation was defined as Meller 1 and 2 (inferior or equal to liver), as reported in previous studies. Demographic and clinical data, as well as disease remission or flares, were recorded and compared to vascular metabolic activity.Results:In total 88 PET scans were performed in 54 LVV-GCA patients, predominantly female (77.8%), aged 68[7,8] years, with a regular BMI (23.9[2.8]) and with a long-standing disease (27[32.6] months). A subsequent PET/MR scan was available in 34 patients (median time between the two scans 9[6.3] months).At first PET examination, low-grade metabolic activity was reported in 68,5% of the cases, while complete remission in 15% and high metabolic activity in 25%. Comparing patients with low-grade vascular inflammation to those with complete remission (Meller 0), they had lower disease duration (28[25.9] vs 73[68] months, but without significance) and they were treated with higher daily prednisone dosage (5[3.8] vs 0[2.2], p=0.042). No significant differences were noted in age, acute phase reactants and type of treatment. Moreover, when compared to those with high metabolic activity (Meller 3), the latter had only significantly higher CRP levels (8.3[13.8] vs 4.1[3.9], p=0.03) and lower disease duration (19[20.6] vs 28[25.9] months, but without significance). While no significant differences were noted in age and type of treatment (both glucocorticoids and immunosuppressants).Among all patients with low-grade vascular inflammation, 81% of them underwent to steroids or immunosuppressants tapering due to clinical remission. At the subsequent PET examination, a worsening of metabolic activity (Meller 3) was found in 4/20 patients, with 1 clinical flare. While in 14/20 patients the subsequent PET revealed a persistent metabolic activity. Only in 2/20 there was a complete metabolic remission. Change or increase of the treatment regimen led to an improvement (Meller 0 or 1) in all the cases. Low-grade metabolic activity was associated with a significant increased risk of worsening/flare at the subsequent PET examination (RR 5.29[1.87-16.11], p=0.002).Conclusion:Low-grade vascular inflammation at PET examination is a common feature in remitted patients. It is associated with older age, lower disease duration and clinical remission. Treatment tapering is associated with an increased risk of worsening/flare. Further research is urgently needed to address this issue.References:[1]J. Meller et al., “Early diagnosis and follow-up of aortitis with [(18)F]FDG PET and MRI.,” Eur. J. Nucl. Med. Mol. Imaging, vol. 30, no. 5, pp. 730–6, May 2003.Disclosure of Interests:Roberto Padoan: None declared, Alessandro Tomelleri: None declared, Mara Felicetti: None declared, Corrado Campochiaro Speakers bureau: Novartis, Pfizer, Roche, GSK, SOBI, Elena Baldissera Speakers bureau: Novartis, Pfizer, Roche, Alpha Sigma, Sanofi, Filippo Crimì: None declared, Pietro Zucchetta: None declared, Diego Cecchin: None declared, Maria Picchio: None declared, Lorenzo Dagna Grant/research support from: Abbvie, BMS, Celgene, Janssen, MSD, Mundipharma Pharmaceuticals, Novartis, Pfizer, Roche, SG, SOBI, Consultant of: Abbvie, Amgen, Biogen, BMS, Celltrion, Novartis, Pfizer, Roche, SG, and SOBI, Andrea Doria Consultant of: GSK, Pfizer, Abbvie, Novartis, Ely Lilly, Speakers bureau: UCB pharma, GSK, Pfizer, Janssen, Abbvie, Novartis, Ely Lilly, BMS, Franco Schiavon: None declared

Optimization of Immobilization Media of Thalassospira Profundimaris: Diffusion and Strength Applications

Many petroleum samples have abundant heterocyclic compounds. One example of petroleum samples is diesel where nitrogen, sulphur and aromatic compounds are the major impurities present in it. Heterocyclic compounds are inextricably into life processes in which a vast number of active heterocyclic compounds are being used. One example of heterocyclic compounds is carbazole which is known to be highly cancinogenic. Bacteria called Thalassospira Profundimaris could potentially degrade the carbazole compounds. The bacteria are immobilized inside media to offer high mechanical strength, high metabolic activity, and resistance to toxic chemicals causing damage to the cell. The media used widely are gellan gum, Ca-alginate and yeast. The finding of the maximum carbazole degradation, optimum strength and diffusivity of the media are profound to increase the performance of the bacteria entrapped inside as well as withstanding the harsh environment around it. This project has proven that the concentration affects the porosity and strength of the media. Increasing the concentration of media would form stronger media with lower diffusivity where lower concentration forms soft media with higher diffusivity.