The mitochondrial calcium uniporter mediates mitochondrial Fe2+ uptake and hepatotoxicity after acetaminophen.

Acetaminophen (APAP) overdose disrupts hepatocellular lysosomes, which release ferrous iron (Fe2+) that translocates into mitochondria putatively via the mitochondrial calcium uniporter (MCU) to induce oxidative/nitrative stress, the mitochondrial permeability transition (MPT), and hepatotoxicity. To investigate how MCU deficiency affects mitochondrial Fe2+ uptake and hepatotoxicity after APAP overdose, global MCU knockout (KO), hepatocyte specific (hs) MCU KO, and wildtype (WT) mice were treated with an overdose of APAP both in vivo and in vitro. Compared to strain-specific WT mice, serum ALT decreased by 88 and 56%, respectively, in global and hsMCU KO mice at 24 h after APAP (300 mg/kg). Hepatic necrosis also decreased by 84 and 56%. By contrast, when MCU was knocked out in Kupffer cells, ALT release and necrosis were unchanged after overdose APAP. Intravital multiphoton microscopy confirmed loss of viability and mitochondrial depolarization in pericentral hepatocytes of WT mice, which was decreased in MCU KO mice. CYP2E1 expression, hepatic APAP-protein adduct formation, and JNK activation revealed that APAP metabolism was equivalent between WT and MCU KO mice. In cultured hepatocytes after APAP, loss of cell viability decreased in hsMCU KO compared to WT hepatocytes. Using fructose plus glycine to prevent cell killing, mitochondrial Fe2+ increased progressively after APAP, as revealed with mitoferrofluor (MFF), a mitochondrial Fe2+ indicator. By contrast in hsMCU KO hepatocytes, mitochondrial Fe2+ uptake after APAP was suppressed. Rhod-2 measurements showed that Ca2+ did not increase in mitochondria after APAP in either WT or KO hepatocytes. In conclusion, MCU mediates uptake of Fe2+ into mitochondria after APAP and plays a central role in mitochondrial depolarization and cell death during APAP-induced hepatotoxicity.

Microhomology-mediated end joining drives complex rearrangements and overexpression of MYC and PVT1 in multiple myeloma.

MYC is a widely acting transcription factor and its deregulation is a crucial event in many human cancers. MYC is important biologically and clinically in multiple myeloma, but the mechanisms underlying its dysregulation are poorly understood. We show that MYC rearrangements are present in 36.0% of newly diagnosed myeloma patients, as detected in the largest set of next generation sequencing data to date (n=1,267). Rearrangements were complex and associated with increased expression of MYC and PVT1, but not other genes at 8q24. The highest effect on gene expression was detected in cases where the MYC locus is juxtaposed next to super-enhancers associated with genes such as IGH, IGK, IGL, TXNDC5/BMP6, FAM46C and FOXO3 We identified three hotspots of recombination at 8q24, one of which is enriched for IGH-MYC translocations. Breakpoint analysis indicates primary myeloma rearrangements involving the IGH locus occur through non-homologous end joining, whereas secondary MYC rearrangements occur through microhomology-mediated end joining. This mechanism is different to lymphomas, where non-homologous end joining generates MYC rearrangements. Rearrangements resulted in overexpression of key genes and chromatin immunoprecipitation-sequencing identified that HK2, a member of the glucose metabolism pathway, is directly over-expressed through binding of MYC at its promoter.

Platelet Glycoprotein VI Haplotypes and the Presentation of Paediatric Sepsis.

Sepsis triggers a complex series of pathophysiologic events involving inflammatory responses and coagulation abnormalities. While circulating blood platelets are well-characterized for their contributions to coagulation, increasingly platelet-dependent effects on inflammation are being recognized. Here, we focus on the platelet membrane receptor, glycoprotein VI (GPVI), and its role in platelet microparticle (pMP) release. The GPVI receptor is a platelet-specific collagen membrane receptor that, upon ligand binding, facilitates the release of pMPs. As membrane-bound platelet fragments of less than 1 µm, pMPs are known to have both pro-inflammatory and pro-coagulant properties. Thus, pMPs are potentially impacting sepsis at multiple stages of the inflammatory response. Studies are presented documenting the impact of the most common GPVI haplotypes, GPVIa and GPVIb, on pMP levels and release in healthy individuals (n = 49). The GPVIa haplotype corresponds to an approximately twofold increase in circulating pMPs as a percentage of total microparticles in healthy individuals along with a heightened in vitro release of pMPs. Additionally, patients admitted to a paediatric intensive care unit (ICU) (n = 73) with an initial diagnosis of sepsis were recruited and their GPVI haplotypes determined. Septic patients of the GPVIa haplotype (n = 59) were statistically more likely to present with a diagnosis of severe sepsis or septic shock, as compared with GPVIb individuals (n = 14). Independent disease classification via PELOD-2 and Pediatric Risk of Mortality III scores confirmed individuals with the GPVIa haplotype were more likely to have significant organ failure. Thus, GPVI haplotypes influence pMP levels in the circulation and are predictive of sepsis severity when presenting to the ICU.

Real-time monitoring of circulating tumor cell (CTC) release after nanodrug or tumor radiotherapy using in vivo flow cytometry.

Noninvasive biological readouts of tumor metastatic risk and therapeutic efficacy are needed as healthcare costs rise. CTCs are the source of metastasis in distant organs that are responsible for the majority of cancer-related deaths. Here we demonstrate the acute and long-term effect of vascular disrupting therapies (high-dose radiotherapy and tumor necrosis factor-alpha (TNF)) on CTCs released from the primary tumor with a non-invasive real-time in vivo flow cytometry system. Using our innovative flow cytometry platform, we show here that radiation and nanodrug treatment can lead to short term release of CTC from the primary tumor. There was no increase in metastasis frequency or extent between control and TNF-treated mice; however, a significant reduction in lung metastasis was noted in the radiotherapy alone group. Mice treated with both TNF and radiotherapy had a slightly elevated metastatic profile between that of radiation alone and control (untreated) tumors. Possible mechanisms based on therapy specific vessel disruption and cell death are discussed. Overall, CTCs correlated with tumor progression and suggest CTC enumeration described herein may be useful in clinical management of solid tumor malignancies.

Combination of Gold Nanoparticle-Conjugated Tumor Necrosis Factor-α and Radiation Therapy Results in a Synergistic Antitumor Response in Murine Carcinoma Models.

PURPOSE: Although remarkable preclinical antitumor effects have been shown for tumor necrosis factor-α (TNF) alone and combined with radiation, its clinical use has been hindered by systemic dose-limiting toxicities. We investigated the physiological and antitumor effects of radiation therapy combined with the novel nanomedicine CYT-6091, a 27-nm average-diameter polyethylene glycol-TNF-coated gold nanoparticle, which recently passed through phase 1 trials. METHODS AND MATERIALS: The physiologic and antitumor effects of single and fractionated radiation combined with CYT-6091 were studied in the murine 4T1 breast carcinoma and SCCVII head and neck tumor squamous cell carcinoma models. RESULTS: In the 4T1 murine breast tumor model, we observed a significant reduction in the tumor interstitial fluid pressure (IFP) 24 hours after CYT-6091 alone and combined with a radiation dose of 12 Gy (P<.05 vs control). In contrast, radiation alone (12 Gy) had a negligible effect on the IFP. In the SCCVII head and neck tumor model, the baseline IFP was not markedly elevated, and little additional change occurred in the IFP after single-dose radiation or combined therapy (P>.05 vs control) despite extensive vascular damage observed. The IFP reduction in the 4T1 model was also associated with marked vascular damage and extravasation of red blood cells into the tumor interstitium. A sustained reduction in tumor cell density was observed in the combined therapy group compared with all other groups (P<.05). Finally, we observed a more than twofold delay in tumor growth when CYT-6091 was combined with a single 20-Gy radiation dose-notably, irrespective of the treatment sequence. Moreover, when hypofractionated radiation (12 Gy × 3) was applied with CYT-6091 treatment, a more than five-fold growth delay was observed in the combined treatment group of both tumor models and determined to be synergistic. CONCLUSIONS: Our results have demonstrated that TNF-labeled gold nanoparticles combined with single or fractionated high-dose radiation therapy is effective in reducing IFP and tumor growth and shows promise for clinical translation.

Platelet glycoprotein Ib-IX as a regulator of systemic inflammation.

OBJECTIVE: The platelet glycoprotein Ib-IX (GP Ib-IX) receptor is a well-characterized adhesion receptor supporting hemostasis and thrombosis via interactions with von Willebrand factor. We examine the GP Ib-IX/von Willebrand factor axis in murine polymicrobial sepsis, as modeled by cecal ligation and puncture (CLP). APPROACH AND RESULTS: Genetic absence of the GP Ib-IX ligand, von Willebrand factor, prolongs survival after CLP, but absence of the receptor, GP Ib-IX, does not. Because absence of either von Willebrand factor or GP Ib-IX significantly impairs hemostasis and thrombosis, we sought to define additional GP Ib-IX-dependent pathways impacting survival in the CLP model. We document that the absence of GP Ib-IX leads to reduced platelet-neutrophil and platelet-monocyte interactions. Twenty-four hours after CLP, absence of GP Ib-IX coincides with an alteration in cytokine levels, such as tumor necrosis factor-α secreted by monocytes, and increased macrophage-1 antigen expression by neutrophils. CONCLUSIONS: In contrast to the well-characterized proinflammatory properties of platelets, we describe in the CLP model an anti-inflammatory property associated with platelet GP Ib-IX. Thus, a single platelet receptor displays a dual modulatory role in both the thrombotic and inflammatory pathways associated with polymicrobial sepsis. In sharing leucine-rich motifs with toll-like receptors, platelet GP Ib-IX can be considered a multifunctional participant in hemostasis, thrombosis, and the inflammatory cascade. The results highlight a dynamic role for platelets in systemic inflammation and add to the complex pathophysiologic events that occur during the dysregulated coagulation and inflammation associated with sepsis.

A comparison of washed and volume-reduced platelets with respect to platelet activation, aggregation, and plasma protein removal.

BACKGROUND: Washed or volume-reduced platelets (PLTs) are occasionally requested for patients with a history of allergic or anaphylactic transfusion reactions. However, conclusive data are not available as to which method is more suitable. STUDY DESIGN AND METHODS: A direct comparison of saline-washed and volume-reduced PLTs was performed by splitting 11 units of 6-day-old apheresis PLT units. PLT activation, aggregation, plasma protein, and PLT count were determined before and after each procedure. To assess whether washing using neutral, calcium-free Ringer's acetate (NRA) would better preserve PLT function, 8 additional units of apheresis PLTs were split and were washed in saline or NRA. RESULTS: Saline washing resulted in significantly increased number of activated, P-selectin-expressing PLTs compared to volume reduction (24.2% vs. 10.3%, p = 0.001). Aggregation was also significantly reduced (-40.6% vs. -0.8%, p = 0.004). Plasma protein removal was significantly better for saline-washed than volume-reduced PLTs (96% vs. 51.1%, p < 0.001). PLT recovery was not significantly different for saline-washed versus volume-reduced PLTs (70.5% vs. 80.7%, p = 0.079). There was no difference between washing in saline or NRA with regard to PLT activation and loss of aggregation. CONCLUSIONS: PLT washing with saline or NRA significantly increases PLT activation and decreases PLT aggregability. On the other hand, volume reduction does not adequately remove plasma proteins. Therefore, PLT washing should be reserved for patients with a history of severe allergic or anaphylactic transfusion reactions. We suggest that fresher PLTs be selected to improve the functionality of washed PLTs.

Platelet glycoprotein Ib alpha supports experimental lung metastasis.

The platelet paradigm in hemostasis and thrombosis involves an initiation step that depends on platelet membrane receptors binding to ligands on a damaged or inflamed vascular surface. Once bound to the surface, platelets provide a unique microenvironment supporting the accumulation of more platelets and the elaboration of a fibrin-rich network produced by coagulation factors. The platelet-specific receptor glycoprotein (GP) Ib-IX, is critical in this process and initiates the formation of a platelet-rich thrombus by tethering the platelet to a thrombogenic surface. A role for platelets beyond the hemostasis/thrombosis paradigm is emerging with significant platelet contributions in both tumorigenesis and inflammation. We have established congenic (N10) mouse colonies (C57BL/6J) with dysfunctional GP Ib-IX receptors in our laboratory that allow us an opportunity to examine the relevance of platelet GP Ib-IX in syngeneic mouse models of experimental metastasis. Our results demonstrate platelet GP Ib-IX contributes to experimental metastasis because a functional absence of GP Ib-IX correlates with a 15-fold reduction in the number of lung metastatic foci using B16F10.1 melanoma cells. The results demonstrate that the extracellular domain of the alpha-subunit of GP Ib is the structurally relevant component of the GP Ib-IX complex contributing to metastasis. Our results support the hypothesis that platelet GP Ib-IX functions that support normal hemostasis or pathologic thrombosis also contribute to tumor malignancy.

Human septin-septin interactions as a prerequisite for targeting septin complexes in the cytosol.

Septins are a cytosolic GTP-binding protein family first characterized in yeast, but gaining increasing recognition as critical protagonists in higher eukaryotic cellular events. Mammalian septins have been associated with cytokinesis and exocytosis, along with contributing to the development of neurological disorders. Ten different septins, divided into four groups, have been identified in mammals, and individual septins are capable of interacting with each other to form macromolecular complexes. The present study characterizes the structural requirements for human septin-septin interactions using a yeast two-hybrid system. We focus on three septins that are highly expressed in platelets and neurons, SEPT4 [previously designated H5, CDCrel-2 (cell-division-control-related-2), PNUTL2], SEPT5 (CDCrel-1, PNUTL1) and SEPT8 (KIAA0202). Each of these three septins contains a characteristic domain structure consisting of unique N- and C-termini, and a central core domain conserved among the family of proteins. The yeast two-hybrid system yielded data consistent with a model where each of the three septins can interact with itself (homotypic assembly) or with one of the other septins (heterotypic assembly). For SEPT5 and SEPT8, the results illustrate a model whereby heterotypic septin assembly is dependent on the conserved central core domain and homotypic interactions require the N- and C-termini of each protein. We also characterized a model in which the proper cellular localization of SEPT5 and SEPT8 requires concomitant expression of both proteins. Co-transfection of SEPT5 and SEPT8 results in both proteins targeted to a vesicular-like location. Therefore the cellular repertoire of human septins has an impact on function by targeting septin macromolecular complexes to specific cellular locations.

A prototypic platelet septin and its participation in secretion.

Studies are presented characterizing platelet CDCrel-1, a protein expressed to high levels by megakaryocytes and belonging to a family of conserved proteins, termed septin. Septin filaments originally were identified in yeast as essential for budding but have become increasingly associated with processes in higher eukaryotic cells involving active membrane movement such as cytokinesis and vesicle trafficking. Direct proof of an in vivo function for septins in higher eukaryotes is limited to the characterization of the Drosophila septin, termed PNUT. We present studies identifying platelet CDCrel-1 as a protein kinase substrate in the presence of known platelet agonists. The immunopurification of CDCrel-1 revealed it to be part of a macromolecular complex containing a protein involved in platelet secretion, syntaxin 4. Moreover, CDCrel-1 was localized in situ to areas surrounding platelet-storage granules. The relevance of CDCrel-1 to normal platelet function was established with the characterization of platelets from a CDCrel-1(Null) mouse. As compared with platelets from wild-type littermates, CDCrel-1(Null) platelets aggregate and release stored [14C]serotonin in the presence of subthreshold levels of collagen. These results provide new insights into the mechanisms regulating platelet secretion and identify platelet septins as a protein family contributing to membrane trafficking within the megakaryocyte and platelet.