Nonalcoholic steatohepatitis severity is defined by a failure in compensatory antioxidant capacity in the setting of mitochondrial dysfunction

AIM To comprehensively evaluate mitochondrial(dys) function in preclinical models of nonalcoholic steatohepatitis(NASH).METHODS We utilized two readily available mouse models of nonalcoholic fatty liver disease(NAFLD) with or without progressive fibrosis: Lep^(ob)/Lep^(ob)(ob/ob) and FATZO mice on high trans-fat, high fructose and high cholesterol(AMLN) diet. Presence of NASH was assessed using immunohistochemical and pathological techniques, and gene expression profiling. Morphological features of mitochondria were assessed via transmission electron microscopy and immunofluorescence, and function was assessed by measuring oxidative capacity in primary hepatocytes, and respiratory control and proton leak in isolated mitochondria. Oxidative stress was measured by assessing activity and/or expression levels of Nrf1, Sod1, Sod2, catalase and 8-OHdG. RESULTS When challenged with AMLN diet for 12 wk, ob/ob and FATZO mice developed steatohepatitis in the presence of obesity and hyperinsulinemia. NASH development was associated with hepatic mitochondrial abnormalities, similar to those previously observed in humans, including mitochondrial accumulation and increased proton leak. AMLN diet also resulted in increased numbers of fragmented mitochondria in both strains of mice. Despite similar mitochondrial phenotypes, we found that ob/ob mice developed more advanced hepatic fibrosis. Activity of superoxide dismutase(SOD) was increased in ob/ob AMLN mice, whereas FATZO mice displayed increased catalase activity, irrespective of diet. Furthermore, 8-OHd G, a marker of oxidative DNA damage, was significantly increased in ob/ob AMLN mice compared to FATZO AMLN mice. Therefore, antioxidant capacity reflected as the ratio of catalase:SOD activity was similar between FATZO and C57 BL6 J control mice, but significantly perturbed in ob/ob mice. CONCLUSION Oxidative stress, and/or the capacity to compensate for increased oxidative stress, in the setting of mitochondrial dysfunction, is a key factor for development of hepatic injury and fibrosis in these mouse models.

Cancer stem cell plasticity and tumor hierarchy

The origins of the complex process of intratumoral heterogeneity have been highly debated and different cellular mechanisms have been hypothesized to account for the diversity within a tumor. The clonal evolution and cancer stem cell(CSC) models have been proposed as drivers of this heterogeneity. However, the concept of cancer stem cell plasticity and bidirectional conversion between stem and non-stem cells has added additional complexity to these highly studied paradigms and may help explain the tumor heterogeneity observed in solid tumors. The process of cancer stem cell plasticity in which cancer cel s harbor the dynamic ability of shifting from a non-CSC state to a CSC state and vice versa may be modulated by specific microenvironmental signals and cellular interactions arising in the tumor niche. In addition to promoting CSC plasticity, these interactions may contribute to the cellular transformation of tumor cells and affect response to chemotherapeutic and radiation treatments by providing CSCs protection from these agents. Herein, we review the literature in support of this dynamic CSC state, discuss the effectors of plasticity, and examine their role in the development and treatment of cancer.

Towards a standard diet-induced and biopsy-confirmed mouse model of non-alcoholic steatohepatitis: Impact of dietary fat source

BACKGROUND The trans-fat containing AMLN(amylin liver non-alcoholic steatohepatitis,NASH)diet has been extensively validated in C57BL/6J mice with or without the Lep^ob/Lep^ob(ob/ob)mutation in the leptin gene for reliably inducing metabolic and liver histopathological changes recapitulating hallmarks of NASH.Due to a recent ban on trans-fats as food additive,there is a marked need for developing a new diet capable of promoting a compatible level of disease in ob/ob and C57BL/6J mice.AIM To develop a biopsy-confirmed mouse model of NASH based on an obesogenic diet with trans-fat substituted by saturated fat.METHODS Male ob/ob mice were fed AMLN diet or a modified AMLN diet with trans-fat(Primex shortening)substituted by equivalent amounts of palm oil[Gubra amylin NASH,(GAN)diet]for 8,12 and 16 wk.C57BL/6J mice were fed the same diets for 28 wk.AMLN and GAN diets had similar caloric content(40%fat kcal),fructose(22%)and cholesterol(2%)level.RESULTS The GAN diet was more obesogenic compared to the AMLN diet and impaired glucose tolerance.Biopsy-confirmed steatosis,lobular inflammation,hepatocyte ballooning,fibrotic liver lesions and hepatic transcriptome changes were similar in ob/ob mice fed the GAN or AMLN diet.C57BL/6J mice developed a mild to moderate fibrotic NASH phenotype when fed the same diets.CONCLUSION Substitution of Primex with palm oil promotes a similar phenotype of biopsyconfirmed NASH in ob/ob and C57BL/6J mice,making GAN diet-induced obese mouse models suitable for characterizing novel NASH treatments.

Molecularly specific detection of bacterial lipoteichoic acid for diagnosis of prosthetic joint infection of the bone

Discriminating sterile inflammation from infection, especially in cases of aseptic loosening versus an actual prosthetic joint infection, is challenging and has significant treatment implications. Our goal was to evaluate a novel human monoclonal antibody（mAb） probe directed against the Gram-positive bacterial surface molecule lipoteichoic acid（LTA）. Specificity and affinity were assessed in vitro. We then radiolabeled the anti-LTA mAb and evaluated its effectiveness as a diagnostic imaging tool for detecting infection via immuno PET imaging in an in vivo mouse model of prosthetic joint infection（PJI）. In vitro and ex vivo binding of the anti-LTA mAb to pathogenic bacteria was measured with Octet, ELISA, and flow cytometry. The in vivo PJI mouse model was assessed using traditional imaging modalities, including positron emission tomography（PET） with [^（18）F]FDG and [^（18）F]Na F as well as X-ray computed tomography（CT）, before being evaluated with the zirconium-89-labeled antibody specific for LTA（[^（89）Zr]SAC55）.The anti-LTA mAb exhibited specific binding in vitro to LTA-expressing bacteria. Results from imaging showed that our model could reliably simulate infection at the surgical site by bioluminescent imaging, conventional PET tracer imaging, and bone morphological changes by CT. One day following injection of both the radiolabeled anti-LTA and isotype control antibodies, the anti-LTA antibody demonstrated significantly greater（P 〈 0.05） uptake at S. aureus-infected prosthesis sites over either the same antibody at sterile prosthesis sites or of control non-specific antibody at infected prosthesis sites. Taken together, the radiolabeled anti-LTA mAb, [^（89）Zr]SAC55, may serve as a valuable diagnostic molecular imaging probe to help distinguish between sterile inflammation and infection in the setting of PJI. Future studies are needed to determine whether these findings will translate to human PJI.

Coronavirus disease 2019 (COVID-19), MERS and SARS: Similarity and difference

SARS-CoV-2 is the causative agent of COVID-19.Since its outbreak in December 2019,COVID-19 has swept the globe.By 17 July 2020,the World Health Organization(WHO)had confirmed 13?119?239 cases and 573?752 deaths,and the numbers are still rising.Current evidence shows that COVID-19 is lower than severe acute respiratory syndrome and Middle East respiratory syndrome in terms of severity and mortality risk,although the infections are particularly more severe in patients with underlying medical conditions.The bulk of COVID-19 patients had close contact with confirmed cases,but an exact origin and specific transmission for COVID-19 are still unknown.As there is no approved antiviral treatment for COVID-19 infection,proper prevention and control practices are essential to control the infection.To have an insight view of COVID-19,we summarized and compared the etiology,clinical manifestations,diagnosis,treatment,and prevention measures of COVID-19,severe acute respiratory syndrome,and Middle East respiratory syndrome.

B7-H7 (HHLA2) inhibits T-cell activation and proliferation in the presence of TCR and CD28 signaling

Modulation of T-cell responses has played a key role in treating cancers and autoimmune diseases.Therefore,understanding how different receptors on T cells impact functional outcomes is crucial.The influence of B7-H7(HHLA2)and CD28H(TMIGD2)on T-cell activation remains controversial.Here we examined global transcriptomic changes in human T cells induced by B7-H7.Stimulation through TCR with OKT3 and B7-H7 resulted in modest fold changes in the expression of select genes;however,these fold changes were significantly lower than those induced by OKT3 and B7-1 stimulation.The transcriptional changes induced by OKT3 and B7-H7 were insufficient to provide functional stimulation as measured by evaluating T-cell proliferation and cytokine production.Interestingly,B7-H7 was coinhibitory when simultaneously combined with TCR and CD28 stimulation.This inhibitory activity was comparable to that observed with PD-L1.Finally,in physiological assays using T cells and APCs,blockade of B7-H7 enhanced T-cell activation and proliferation,demonstrating that this ligand acts as a break signal.Our work defines that the transcriptomic changes induced by B7-H7 are insufficient to support full costimulation with TCR signaling and,instead,B7-H7 inhibits T-cell activation and proliferation in the presence of TCR and CD28 signaling.