Diagnosing arsenic-mediated biochemical responses in rice cultivars using Raman spectroscopy

Rice (Oryza sativa) is the primary crop for nearly half of the world's population. Groundwater in many rice-growing parts of the world often has elevated levels of arsenite and arsenate. At the same time, rice can accumulate up to 20 times more arsenic compared to other staple crops. This places an enormous amount of people at risk of chronic arsenic poisoning. In this study, we investigated whether Raman spectroscopy (RS) could be used to diagnose arsenic toxicity in rice based on biochemical changes that were induced by arsenic accumulation. We modeled arsenite and arsenate stresses in four different rice cultivars grown in hydroponics over a nine-day window. Our results demonstrate that Raman spectra acquired from rice leaves, coupled with partial least squares-discriminant analysis, enabled accurate detection and identification of arsenic stress with approximately 89% accuracy. We also performed high-performance liquid chromatography (HPLC)-analysis of rice leaves to identify the key molecular analytes sensed by RS in confirming arsenic poisoning. We found that RS primarily detected a decrease in the concentration of lutein and an increase in the concentration of vanillic and ferulic acids due to the accumulation of arsenite and arsenate in rice. This showed that these molecules are detectable indicators of biochemical response to arsenic accumulation. Finally, a cross-correlation of RS with HPLC and ICP-MS demonstrated RS's potential for a label-free, non-invasive, and non-destructive quantification of arsenic accumulation in rice.

Immunometabolic factors contributing to obesity-linked hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major public health concern that is promoted by obesity and associated liver complications. Onset and progression of HCC in obesity is a multifactorial process involving complex interactions between the metabolic and immune system, in which chronic liver damage resulting from metabolic and inflammatory insults trigger carcinogenesis-promoting gene mutations and tumor metabolism. Moreover, cell growth and proliferation of the cancerous cell, after initiation, requires interactions between various immunological and metabolic pathways that provide stress defense of the cancer cell as well as strategic cell death escape mechanisms. The heterogenic nature of HCC in addition to the various metabolic risk factors underlying HCC development have led researchers to focus on examining metabolic pathways that may contribute to HCC development. In obesity-linked HCC, oncogene-induced modifications and metabolic pathways have been identified to support anabolic demands of the growing HCC cells and combat the concomitant cell stress, coinciding with altered utilization of signaling pathways and metabolic fuels involved in glucose metabolism, macromolecule synthesis, stress defense, and redox homeostasis. In this review, we discuss metabolic insults that can underlie the transition from steatosis to steatohepatitis and from steatohepatitis to HCC as well as aberrantly regulated immunometabolic pathways that enable cancer cells to survive and proliferate in the tumor microenvironment. We also discuss therapeutic modalities targeted at HCC prevention and regression. A full understanding of HCC-associated immunometabolic changes in obesity may contribute to clinical treatments that effectively target cancer metabolism.

In vivo stress reporters as early biomarkers of the cellular changes associated with progeria

Age‐related diseases account for a high proportion of the total global burden of disease. Despite recent advances in understanding their molecular basis, there is a lack of suitable early biomarkers to test selected compounds and accelerate their translation to clinical trials. We have investigated the utility of in vivo stress reporter systems as surrogate early biomarkers of the degenerative disease progression. We hypothesized that cellular stress observed in models of human degenerative disease preceded overt cellular damage and at the same time will identify potential cytoprotective pathways. To test this hypothesis, we generated novel accelerated ageing (progeria) reporter mice by crossing the LmnaG609G mice into our oxidative stress/inflammation (Hmox1) and DNA damage (p21) stress reporter models. Histological analysis of reporter expression demonstrated a time‐dependent and tissue‐specific activation of the reporters in tissues directly associated with Progeria, including smooth muscle cells, the vasculature and gastrointestinal tract. Importantly, reporter expression was detected prior to any perceptible deleterious phenotype. Reporter expression can therefore be used as an early marker of progeria pathogenesis and to test therapeutic interventions. This work also demonstrates the potential to use stress reporter approaches to study and find new treatments for other degenerative diseases.

Stress Pathway Modulation Is Detrimental or Ineffective for Functional Recovery after Spinal Cord Injury in Mice

A mounting body of evidence suggests that stress plays a major role in the injury progression after spinal cord injury (SCI). Injury activates the stress systems; this in turn may augment the generation of pro-inflammatory cytokines, stimulate pro-inflammatory immune cells, and alter the balance between the pro- and anti-inflammatory immune response. As a result, it is suggested that stress pathways may augment neuronal damage and loss after SCI. Considering these potential detrimental effects of stress after SCI, we hypothesized that inhibition of stress pathways immediately after SCI may offer protection from damage and improve recovery. To investigate the relevance of stress responses in SCI recovery, we investigated the effects of blocking three well-studied stress response axes in a mouse model of SCI. Propranolol, RU-486, and CP-99994 were administered to inhibit the sympathetic axis, the hypothalamus-pituitary-adrenal axis, and the neuropeptide axis, respectively. Surprisingly, assessing functional recovery by the Basso Mouse Scale revealed that RU-486 and CP-99994 did not affect functional outcome, indicating that these pathways are dispensable for neuroprotection or repair after SCI. Moreover, the beta-blocker propranolol worsened functional outcome in the mouse SCI model. In conclusion, immediate inhibition of three major stress axes has no beneficial effects on functional recovery after SCI in mice. These results suggest that injury-induced stress responses do not interfere with the healing process and hence, pharmacological targeting of stress responses is not a recommended treatment option for SCI. These findings are of great importance for other researchers to avoid unnecessary and potentially futile animal experiments.

Treatment with AICAR inhibits blastocyst development, trophectoderm differentiation and tight junction formation and function in mice

STUDY QUESTION

What is the impact of adenosine monophosphate-activated protein kinase (AMPK) activation on blastocyst formation, gene expression, and tight junction formation and function?

SUMMARY ANSWER

AMPK activity must be tightly controlled for normal preimplantation development and blastocyst formation to occur.

WHAT IS KNOWN ALREADY

AMPK isoforms are detectable in oocytes, cumulus cells and preimplantation embryos. Cultured embryos are subject to many stresses that can activate AMPK.

STUDY DESIGN, SIZE, DURATION

Two primary experiments were carried out to determine the effect of AICAR treatment on embryo development and maintenance of the blastocoel cavity. Embryos were recovered from superovulated mice. First, 2-cell embryos were treated with a concentration series (0-2000 μM) of AICAR for 48 h until blastocyst formation would normally occur. In the second experiment, expanded mouse blastocysts were treated for 9 h with 1000 μM AICAR.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Outcomes measured included development to the blastocyst stage, cell number, blastocyst volume, AMPK phosphorylation, Cdx2 and blastocyst formation gene family expression (mRNAs and protein measured using quantitative RT-PCR, immunoblotting, immunofluorescence), tight junction function (FITC dextran dye uptake assay), and blastocyst ATP levels. The reversibility of AICAR treatment was assessed using Compound C (CC), a well-known inhibitor of AMPK, alone or in combination with AICAR.

MAIN RESULTS AND THE ROLE OF CHANCE

Prolonged treatment with AICAR from the 2-cell stage onward decreases blastocyst formation, reduces total cell number, embryo diameter, leads to loss of trophectoderm cell contacts and membrane zona occludens-1 staining, and increased nuclear condensation. Treatment with CC alone inhibited blastocyst development only at concentrations that are higher than normally used. AICAR treated embryos displayed altered mRNA and protein levels of blastocyst formation genes. Treatment of blastocysts with AICAR for 9 h induced blastocyst collapse, altered blastocyst formation gene expression, increased tight junction permeability and decreased CDX2. Treated blastocysts displayed three phenotypes: those that were unaffected by treatment, those in which treatment was reversible, and those in which effects were irreversible.

LARGE SCALE DATA

Not applicable.

LIMITATIONS, REASONS FOR CAUTION

Our study investigates the effects of AICAR treatment on early development. While AICAR does increase AMPK activity and this is demonstrated in our study, AICAR is not a natural regulator of AMPK activity and some outcomes may result from off target non-AMPK AICAR regulated events. To support our results, blastocyst developmental outcomes were confirmed with two other well-known small molecule activators of AMPK, metformin and phenformin.

WIDER IMPLICATIONS OF THE FINDINGS

Metformin, an AMPK activator, is widely used to treat type II diabetes and polycystic ovarian disorder (PCOS). Our results indicate that early embryonic AMPK levels must be tightly regulated to ensure normal preimplantation development. Thus, use of metformin should be carefully considered during preimplantation and early post-embryo transfer phases of fertility treatment cycles.

STUDY FUNDING AND COMPETING INTEREST(S)

Canadian Institutes of Health Research (CIHR) operating funds. There are no competing interests.

Cellular resilience

Cellular resilience describes the ability of a cell to cope with environmental changes such as toxicant exposure. If cellular metabolism does not collapse directly after the hit or end in programmed cell death, the ensuing stress responses promote a new homeostasis under stress. The processes of reverting "back to normal" and reversal of apoptosis ("anastasis") have been studied little at the cellular level. Cell types show astonishingly similar vulnerability to most toxicants, except for those that require a very specific target, metabolism or mechanism present only in specific cell types. The majority of chemicals triggers "general cytotoxicity" in any cell at similar concentrations. We hypothesize that cells differ less in their vulnerability to a given toxicant than in their resilience (coping with the "hit"). In many cases, cells do not return to the naive state after a toxic insult. The phenomena of "pre-conditioning", "tolerance" and "hormesis" describe this for low-dose exposures to toxicants that render the cell more resistant to subsequent hits. The defense and resilience programs include epigenetic changes that leave a "memory/scar" - an alteration as a consequence of the stress the cell has experienced. These memories might have long-term consequences, both positive (resistance) and negative, that contribute to chronic and delayed manifestations of hazard and, ultimately, disease. This article calls for more systematic analyses of how cells cope with toxic perturbations in the long-term after stressor withdrawal. A technical prerequisite for these are stable (organotypic) cultures and a characterization of stress response molecular networks.