Autophagy and mitochondrial remodelling in mouse mesenchymal stromal cells challenged with Staphylococcus epidermidis

The bone marrow stroma constitutes the marrow-blood barrier, which sustains immunochemical homoeostasis and protection of the haematopoietic tissue in sequelae of systemic bacterial infections. Under these conditions, the bone marrow stromal cells affected by circulating bacterial pathogens shall elicit the adaptive stress-response mechanisms to maintain integrity of the barrier. The objective of this communication was to demonstrate (i) that in vitro challenge of mesenchymal stromal cells, i.e. colony-forming unit fibroblasts (CFU-F), with Staphylococcus epidermidis can activate the autophagy pathway to execute antibacterial defence response, and (ii) that homoeostatic shift because of the bacteria-induced stress includes the mitochondrial remodelling and sequestration of compromised organelles via mitophagy. Implication of Drp1 and PINK1–PARK2-dependent mechanisms in the mitophagy turnover of the aberrant mitochondria in mesenchymal stromal cells is investigated and discussed.

Ciprofloxacin as a potential radio-sensitizer to tumor cells and a radio-protectant for normal cells: differential effects on γ-H2AX formation, p53 phosphorylation, Bcl-2 production, and cell death

Ionizing radiation increases cell mortality in a dose-dependent manner. Increases in DNA double strand breaks, γ-H2AX, p53 phophorylation, and protein levels of p53 and Bax also occur. We investigated the ability of ciprofloxacin (CIP), a widely prescribed antibiotic, to inhibit DNA damage induced by ionizing radiation. Human tumor TK6, NH32 (p53 (-/-) of TK6) cells, and human normal peripheral blood mononuclear cells (PBMCs) were exposed to 2-8 Gy (60)Co-γ-photon radiation. γ-H2AX (an indicator of DNA strand breaks), phosphorylated p53 (responsible for cell-cycle arrest), Bcl-2 (an apoptotic protein, and cell death were measured. Ionizing irradiation increased γ-H2AX amounts in TK6 cells (p53(+/+)) within 1 h in a radiation dose-dependent manner. CIP pretreatment and posttreatment effectively inhibited the increase in γ-H2AX. CIP pretreatment reduced Bcl-2 production but promoted p53 phosphorylation, caspase-3 activation and cell death. In NH32 cells, CIP failed to significantly inhibit the radiation-induced γ-H2AX increase, suggesting that CIP inhibition involves in p53-dependent mechanisms. In normal healthy human PBMCs, CIP failed to block the radiation-induced γ-H2AX increase but effectively increased Bcl-2 production, but blocked the phospho-p53 increase and subsequent cell death. CIP increased Gadd45α, and enhanced p21 protein 24 h postirradiation. Results suggest that CIP exerts its effect in TK6 cells by promoting p53 phosphorylation and inhibiting Bcl-2 production and in PBMCs by inhibiting p53 phosphorylation and increasing Bcl-2 production. Our data are the first to support the view that CIP may be effective to protect normal tissue cells from radiation injury, while enhancing cancer cell death in radiation therapy.

Adaptive redox response of mesenchymal stromal cells to stimulation with lipopolysaccharide inflammagen: mechanisms of remodeling of tissue barriers in sepsis

Acute bacterial inflammation is accompanied by excessive release of bacterial toxins and production of reactive oxygen and nitrogen species (ROS and RNS), which ultimately results in redox stress. These factors can induce damage to components of tissue barriers, including damage to ubiquitous mesenchymal stromal cells (MSCs), and thus can exacerbate the septic multiple organ dysfunctions. The mechanisms employed by MSCs in order to survive these stress conditions are still poorly understood and require clarification. In this report, we demonstrated that in vitro treatment of MSCs with lipopolysaccharide (LPS) induced inflammatory responses, which included, but not limited to, upregulation of iNOS and release of RNS and ROS. These events triggered in MSCs a cascade of responses driving adaptive remodeling and resistance to a "self-inflicted" oxidative stress. Thus, while MSCs displayed high levels of constitutively present adaptogens, for example, HSP70 and mitochondrial Sirt3, treatment with LPS induced a number of adaptive responses that included induction and nuclear translocation of redox response elements such as NFkB, TRX1, Ref1, Nrf2, FoxO3a, HO1, and activation of autophagy and mitochondrial remodeling. We propose that the above prosurvival pathways activated in MSCs in vitro could be a part of adaptive responses employed by stromal cells under septic conditions.

Wound trauma alters ionizing radiation dose assessment

BACKGROUND

Wounding following whole-body γ-irradiation (radiation combined injury, RCI) increases mortality. Wounding-induced increases in radiation mortality are triggered by sustained activation of inducible nitric oxide synthase pathways, persistent alteration of cytokine homeostasis, and increased susceptibility to bacterial infection. Among these factors, cytokines along with other biomarkers have been adopted for biodosimetric evaluation and assessment of radiation dose and injury. Therefore, wounding could complicate biodosimetric assessments.

RESULTS

In this report, such confounding effects were addressed. Mice were given 60Co γ-photon radiation followed by skin wounding. Wound trauma exacerbated radiation-induced mortality, body-weight loss, and wound healing. Analyses of DNA damage in bone-marrow cells and peripheral blood mononuclear cells (PBMCs), changes in hematology and cytokine profiles, and fundamental clinical signs were evaluated. Early biomarkers (1 d after RCI) vs. irradiation alone included significant decreases in survivin expression in bone marrow cells, enhanced increases in γ-H2AX formation in Lin+ bone marrow cells, enhanced increases in IL-1β, IL-6, IL-8, and G-CSF concentrations in blood, and concomitant decreases in γ-H2AX formation in PBMCs and decreases in numbers of splenocytes, lymphocytes, and neutrophils. Intermediate biomarkers (7 - 10 d after RCI) included continuously decreased γ-H2AX formation in PBMC and enhanced increases in IL-1β, IL-6, IL-8, and G-CSF concentrations in blood. The clinical signs evaluated after RCI were increased water consumption, decreased body weight, and decreased wound healing rate and survival rate. Late clinical signs (30 d after RCI) included poor survival and wound healing.

CONCLUSION

Results suggest that confounding factors such as wounding alters ionizing radiation dose assessment and agents inhibiting these responses may prove therapeutic for radiation combined injury and reduce related mortality.

Response of crypt paneth cells in the small intestine following total-body gamma-irradiation

Ionizing irradiation causes damage and functional failure of irradiation-sensitive systems and tissues such as small intestine. The molecular mechanisms underlying inflammatory and adaptive responses to acute irradiation damage are poorly understood. Using a mouse model of total-body γ-irradiation, we assessed the irradiation response of crypt host-defense Paneth cells by measuring alpha-defensin 4 (AD4) expression and correlated the gathered data with activation of the caspase-1/IL-1β inflammatory signaling cascade. The irradiation injury was produced in CD2F1 mice exposed to 9.25 Gy γ-radiation. This dose resulted in 85-100 percent mortality at the 15(th) day post-irradiation. Small intestine tissue samples were collected at the 7th day post-irradiation. Assessment of irradiation-associated pro-inflammatory alterations in small intestine tissue and expression of AD4 in Paneth cells was conducted using confocal immunofluorescence imaging, transmission electron microscopy (TEM), light microscopy, and immunoblotting techniques. The small intestine analysis revealed an increase in the precursor form of IL-1β, the activated form of IL-1β, and the activated form of caspase-1 (p10 CASP-1) at the 7(th) day post-irradiation. Immunoprecipitation analysis showed increased interaction between IL-1β and p10 CASP-1 after irradiation. This effect was observed in the irradiated small intestine and CD15-positive Paneth cells using confocal imaging techniques. The pro-inflammatory alterations in Paneth cells were accompanied by increases in AD4 mRNA and its 8 kD peptide product. Paneth cell secretory activity was observed at the sites of bacterial translocation in the crypt lumens. These data suggest that Paneth cells can contribute to small intestine inflammatory remodeling during the post-irradiation period.

Radiation Combined Injury: DNA Damage, Apoptosis, and Autophagy

Radiation combined injury is defined as an ionizing radiation exposure received in combination with other trauma or physiological insults. The range of radiation threats we face today includes everything from individual radiation exposures to mass casualties resulting from a terrorist nuclear incident, and many of these exposure scenarios include the likelihood of additional traumatic injury. Radiation combined injury sensitizes target organs and cells and exacerbates acute radiation syndrome. Organs and cells with high sensitivity to combined injury are the skin, the hematopoietic system, the gastrointestinal tract, spermatogenic cells, and the vascular system. Among its many effects, radiation combined injury results in decreases in lymphocytes, macrophages, neutrophils, platelets, stem cells, and tissue integrity; activation of the iNOS/NF-κB/NF-IL6 and p53/Bax pathways; and increases in DNA single and double strand breaks, TLR signaling, cytokine concentrations, bacterial infection, and cytochrome c release from mitochondria to cytoplasm. These alterations lead to apoptosis and autophagy and, as a result, increased mortality. There is a pressing need to understand more about the body's response to combined injury in order to be able to develop effective countermeasures, since few currently exist. In this review, we summarize what is known about how combined injury modifies the radiation response, with a special emphasis on DNA damage/repair, signal transduction pathways, apoptosis, and autophagy. We also describe current and prospective countermeasures relevant to the treatment and prevention of combined injury.

Production of polyhydroxybutyrate in switchgrass, a value-added co-product in an important lignocellulosic biomass crop

Polyhydroxyalkanoate bio-based plastics made from renewable resources can reduce petroleum consumption and decrease plastic waste disposal issues as they are inherently biodegradable in soil, compost and marine environments. In this paper, the successful engineering of the biomass crop switchgrass (Panicum virgatum L.) for the synthesis of polyhydroxybutyrate (PHB) is reported. Polymer production was monitored in more than 400 primary transformants grown under in vitro and glasshouse conditions. Plants containing up to 3.72% dry weight of PHB in leaf tissues and 1.23% dry weight of PHB in whole tillers were obtained. Results from the analysis of the polymer distribution at the cellular and whole plant levels are presented, and target areas for the improvement of PHB production are highlighted. Polymer accumulation was also analysed in the T(1) generation obtained from controlled crosses of transgenic plants. This study presents the first successful expression of a functional multigene pathway in switchgrass, and demonstrates that this high-yielding biomass crop is amenable to the complex metabolic engineering strategies necessary to produce high-value biomaterials with lignocellulose-derived biofuels.