Adaptation to volumetric compression drives hepatoblastoma cells to an apoptosis-resistant and invasive phenotype

Liver cancer involves tumor cells rapidly growing within a packed tissue environment. Patient tumor tissues reveal densely packed and deformed cells, especially at tumor boundaries, indicative of physical crowding and compression. It is not well understood how these physical signals modulate tumor evolution and therapeutic susceptibility. Here we investigate the impact of volumetric compression on liver cancer (HepG2) behavior. We find that conditioning cells under a highly compressed state leads to major transcriptional reprogramming, notably the loss of hepatic markers, the epithelial-to-mesenchymal transition (EMT)-like changes, and altered calcium signaling-related gene expression, over the course of several days. Biophysically, compressed cells exhibit increased Rac1-mediated cell spreading and cell-extracellular matrix interactions, cytoskeletal reorganization, increased YAP and β-catenin nuclear translocation, and dysfunction in cytoplasmic and mitochondrial calcium signaling. Furthermore, compressed cells are resistant to chemotherapeutics and desensitized to apoptosis signaling. Apoptosis sensitivity can be rescued by stimulated calcium signaling. Our study demonstrates that volumetric compression is a key microenvironmental factor that drives tumor evolution in multiple pathological directions and highlights potential countermeasures to re-sensitize therapy-resistant cells.

Significance statement

Compression can arise as cancer cells grow and navigate within the dense solid tumor microenvironment. It is unclear how compression mediates critical programs that drive tumor progression and therapeutic complications. Here, we take an integrative approach in investigating the impact of compression on liver cancer. We identify and characterize compressed subdomains within patient tumor tissues. Furthermore, using in vitro systems, we induce volumetric compression (primarily via osmotic pressure but also via mechanical force) on liver cancer cells and demonstrate significant molecular and biophysical changes in cell states, including in function, cytoskeletal signaling, proliferation, invasion, and chemoresistance. Importantly, our results show that compressed cells have impaired calcium signaling and acquire resistance to apoptosis, which can be countered via calcium mobilization.

Calcium signaling in chemotherapy-induced neuropathy

Alterations in calcium (Ca²⁺) signaling is a major mechanism in the development of chemotherapy-induced peripheral neuropathy (CIPN), a side effect caused by multiple chemotherapy regimens. CIPN is associated with numbness and incessant tingling in hands and feet which diminishes quality of life during treatment. In up to 50% of survivors, CIPN is essentially irreversible. There are no approved, disease-modifying treatments for CIPN. The only recourse for oncologists is to modify the chemotherapy dose, a situation that can compromise optimal chemotherapy and impact patient outcomes. Here we focus on taxanes and other chemotherapeutic agents that work by altering microtubule assemblies to kill cancer cells, but also have off-target toxicities. There have been many molecular mechanisms proposed to explain the effects of microtubule-disrupting drugs. In neurons, an initiating step in the off-target effects of treatment by taxane is binding to neuronal calcium sensor 1 (NCS1), a sensitive Ca²⁺ sensor protein that maintains the resting Ca²⁺ concentration and dynamically enhances responses to cellular stimuli. The taxane/NCS1 interaction causes a Ca²⁺ surge that starts a pathophysiological cascade of consequences. This same mechanism contributes to other conditions including chemotherapy-induced cognitive impairment. Strategies to prevent the Ca²⁺ surge are the foundation of current work.

The des-Arg9-bradykinin/B1R axis: Hepatic damage in COVID-19

Patients infected by the SARS-CoV-2 virus are commonly diagnosed with threatening liver conditions associated with drug-induced therapies and systemic viral action. RNA-Seq data from cells in bronchoalveolar lavage fluid from COVID-19 patients have pointed out dysregulation of kallikrein-kinin and renin-angiotensin systems as a possible mechanism that triggers multi-organ damage away from the leading site of virus infection. Therefore, we measured the plasma concentration of biologically active peptides from the kallikrein-kinin system, bradykinin and des-Arg⁹-bradykinin, and liver expression of its proinflammatory axis, bradykinin 1 receptor (B1R). We measured the plasma concentration of bradykinin and des-Arg⁹-bradykinin of 20 virologically confirmed COVID-19 patients using a liquid chromatography-tandem mass spectrometry-based methodology. The expression of B1R was evaluated by immunohistochemistry from post-mortem liver specimens of 27 COVID-19 individuals. We found a significantly higher blood level of des-Arg⁹-bradykinin and a lower bradykinin concentration in patients with COVID-19 compared to a healthy, uninfected control group. We also observed increased B1R expression levels in hepatic tissues of patients with COVID-19 under all hepatic injuries analyzed (liver congestion, portal vein dilation, steatosis, and ischemic necrosis). Our data indicate that des-Arg⁹-bradykinin/B1R is associated with the acute hepatic dysfunction induced by the SARS-CoV-2 virus infection in the pathogenesis of COVID-19.

Correlation Between Clinical and Pathological Findings of Liver Injury in 27 Patients With Lethal COVID-19 Infections in Brazil

Liver test abnormalities are frequently observed in patients with coronavirus disease 2019 (COVID‐19) and are associated with worse prognosis. However, information is limited about pathological changes in the liver in this infection, so the mechanism of liver injury is unclear. Here we describe liver histopathology and clinical correlates of 27 patients who died of COVID‐19 in Manaus, Brazil. There was a high prevalence of liver injury (elevated alanine aminotransferase and aspartate aminotransferase in 44% and 48% of patients, respectively) in these patients. Histological analysis showed sinusoidal congestion and ischemic necrosis in more than 85% of the cases, but these appeared to be secondary to systemic rather than intrahepatic thrombotic events, as only 14% and 22% of samples were positive for CD61 (marker of platelet activation) and C4d (activated complement factor), respectively. Furthermore, the extent of these vascular findings did not correlate with the extent of transaminase elevations. Steatosis was present in 63% of patients, and portal inflammation was present in 52%. In most cases, hepatocytes expressed angiotensin‐converting enzyme 2 (ACE2), which is responsible for binding and entry of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), even though this ectoenzyme was minimally expressed on hepatocytes in normal controls. However, SARS‐CoV‐2 staining was not observed. Most hepatocytes also expressed inositol 1,4,5‐triphosphate receptor 3 (ITPR3), a calcium channel that becomes expressed in acute liver injury. Conclusion: The hepatocellular injury that commonly occurs in patients with severe COVID‐19 is not due to the vascular events that contribute to pulmonary or cardiac damage. However, new expression of ACE2 and ITPR3 with concomitant inflammation and steatosis suggests that liver injury may result from inflammation, metabolic abnormalities, and perhaps direct viral injury.

Inositol 1,4,5-trisphosphate receptor type 3 plays a protective role in hepatocytes during hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury is seen in a variety of clinical conditions, including hepatic thrombosis, systemic hypotension, and liver transplantation. Calcium (Ca²⁺) signaling mediates several pathophysiological processes in the liver, but it is not known whether and how intracellular Ca²⁺ channels are involved in the hepatocellular events secondary to ischemia-reperfusion. Using an animal model of hepatic ischemia-reperfusion injury, we observed a progressive increase in expression of the type 3 isoform of the inositol trisphosphate receptor (ITPR3), an intracellular Ca²⁺ channel that is not normally expressed in healthy hepatocytes. ITPR3 expression was upregulated, at least in part, by a combination of demethylation of the ITPR3 promoter region and the increased transcriptional activity of the nuclear factor of activated T-cells (NFAT). Additionally, expression of pro-inflammatory interleukins and necrotic surface area were less pronounced in livers of control animals compared to liver-specific ITPR3 KO mice subjected to hepatic damage. Corroborating these findings, ITPR3 expression and activation of NFAT were observed in hepatocytes of liver biopsies from patients who underwent liver ischemia caused by thrombosis after organ transplant. Together, these results are consistent with the idea that ITPR3 expression in hepatocytes plays a protective role during hepatic injury induced by ischemia-reperfusion.

Molecular Mechanism for Protection Against Liver Failure in Human Yellow Fever Infection

Yellow fever (YF) is a viral hemorrhagic fever that typically involves the liver. Brazil recently experienced its largest recorded YF outbreak, and the disease was fatal in more than a third of affected individuals, mostly because of acute liver failure. Affected individuals are generally treated only supportively, but during the recent Brazilian outbreak, selected patients were treated with liver transplant. We took advantage of this clinical experience to better characterize the clinical and pathological features of YF-induced liver failure and to examine the mechanism of hepatocellular injury in YF, to identify targets that would be amenable to therapeutic intervention in preventing progression to liver failure and death. Patients with YF liver failure rapidly developed massive transaminase elevations, with jaundice, coagulopathy, thrombocytopenia, and usually hepatic encephalopathy, along with pathological findings that included microvesicular steatosis and lytic necrosis. Hepatocytes began to express the type 3 isoform of the inositol trisphosphate receptor (ITPR3), an intracellular calcium (Ca2+) channel that is not normally expressed in hepatocytes. Experiments in an animal model, isolated hepatocytes, and liver-derived cell lines showed that this new expression of ITPR3 was associated with increased nuclear Ca2+ signaling and hepatocyte proliferation, and reduced steatosis and cell death induced by the YF virus. Conclusion: Yellow fever often induces liver failure characterized by massive hepatocellular damage plus steatosis. New expression of ITPR3 also occurs in YF-infected hepatocytes, which may represent an endogenous protective mechanism that could suggest approaches to treat affected individuals before they progress to liver failure, thereby decreasing the mortality of this disease in a way that does not rely on the costly and limited resource of liver transplantation.

Inositol 1,4,5-trisphosphate receptor in the liver: Expression and function

The liver is a complex organ that performs several functions to maintain homeostasis. These functions are modulated by calcium, a second messenger that regulates several intracellular events. In hepatocytes and cholangiocytes, which are the epithelial cell types in the liver, inositol 1,4,5-trisphosphate (InsP₃) receptors (ITPR) are the only intracellular calcium release channels. Three isoforms of the ITPR have been described, named type 1, type 2 and type 3. These ITPR isoforms are differentially expressed in liver cells where they regulate distinct physiological functions. Changes in the expression level of these receptors correlate with several liver diseases and hepatic dysfunctions. In this review, we highlight how the expression level, modulation, and localization of ITPR isoforms in hepatocytes and cholangiocytes play a role in hepatic homeostasis and liver pathology.

Polymorphism in the Promoter Region of NFE2L2 Gene Is a Genetic Marker of Susceptibility to Cirrhosis Associated with Alcohol Abuse

Alcoholic liver disease (ALD) is a highly prevalent spectrum of pathologies caused by alcohol overconsumption. Morbidity and mortality related to ALD are increasing worldwide, thereby demanding strategies for early diagnosis and detection of ALD predisposition. A potential candidate as a marker for ALD susceptibility is the transcription factor nuclear factor erythroid-related factor 2 (Nrf2), codified by the nuclear factor erythroid 2-related factor 2 gene (NFE2L2). Nrf2 regulates expression of proteins that protect against oxidative stress and inflammation caused by alcohol overconsumption. Here, we assessed genetic variants of NFE2L2 for association with ALD. Specimens from patients diagnosed with cirrhosis caused by ALD were genotyped for three NFE2L2 single nucleotide polymorphisms (SNP) (SNPs: rs35652124, rs4893819, and rs6721961). Hematoxylin & eosin and immunohistochemistry were performed to determine the inflammatory score and Nrf2 expression, respectively. SNPs rs4893819 and rs6721961 were not specifically associated with ALD, but analysis of SNP rs35652124 suggested that this polymorphism predisposes to ALD. Furthermore, SNP rs35652124 was associated with a lower level of Nrf2 expression. Moreover, liver samples from ALD patients with this polymorphism displayed more severe inflammatory activity. Together, these findings provide evidence that the SNP rs35652124 variation in the Nrf2-encoding gene NFE2L2 is a potential genetic marker for susceptibility to ALD.

Effects of Endotoxin on Type 3 Inositol 1,4,5-Trisphosphate Receptor in Human Cholangiocytes

Clinical conditions that result in endotoxemia, such as sepsis and alcoholic hepatitis (AH), often are accompanied by cholestasis. Although hepatocellular changes in response to lipopolysaccharide (LPS) have been well characterized, less is known about whether and how cholangiocytes contribute to this form of cholestasis. We examined effects of endotoxin on expression and function of the type 3 inositol trisphosphate receptor (ITPR3), because this is the main intracellular Ca²⁺ release channel in cholangiocytes, and loss of it impairs ductular bicarbonate secretion. Bile duct cells expressed the LPS receptor, Toll-like receptor 4 (TLR4), which links to activation of nuclear factor-κB (NF-κB). Analysis of the human ITPR3 promoter revealed five putative response elements to NF-κB, and promoter activity was inhibited by p65/p50. Nested 0.5- and 1.0-kilobase (kb) deletion fragments of the ITPR3 promoter were inhibited by NF-κB subunits. Chromatin immunoprecipitation (ChIP) assay showed that NF-κB interacts with the ITPR3 promoter, with an associated increase in H3K9 methylation. LPS decreased ITPR3 mRNA and protein expression and also decreased sensitivity of bile duct cells to calcium agonist stimuli. This reduction was reversed by inhibition of TLR4. ITPR3 expression was decreased or absent in cholangiocytes from patients with cholestasis of sepsis and from those with severe AH. Conclusion: Stimulation of TLR4 by LPS activates NF-κB to down-regulate ITPR3 expression in human cholangiocytes. This may contribute to the cholestasis that can be observed in conditions such as sepsis or AH.

GPR91: expanding the frontiers of Krebs cycle intermediates

Since it was discovered, the citric acid cycle has been known to be central to cell metabolism and energy homeostasis. Mainly found in the mitochondrial matrix, some of the intermediates of the Krebs cycle are also present in the blood stream. Currently, there are several reports that indicate functional roles for Krebs intermediates out of its cycle. Succinate, for instance, acts as an extracellular ligand by binding to a G-protein coupled receptor, known as GPR91, expressed in kidney, liver, heart, retinal cells and possibly many other tissues, leading to a wide array of physiological and pathological effects. Through GPR91, succinate is involved in functions such as regulation of blood pressure, inhibition of lipolysis in white adipose tissue, development of retinal vascularization, cardiac hypertrophy and activation of stellate hepatic cells by ischemic hepatocytes. Along the current review, these new effects of succinate through GPR91 will be explored and discussed.

Decoding calcium signaling across the nucleus

Calcium (Ca(2+)) is an important multifaceted second messenger that regulates a wide range of cellular events. A Ca(2+)-signaling toolkit has been shown to exist in the nucleus and to be capable of generating and modulating nucleoplasmic Ca(2+) transients. Within the nucleus, Ca(2+) controls cellular events that are different from those modulated by cytosolic Ca(2+). This review focuses on nuclear Ca(2+) signals and their role in regulating physiological and pathological processes.

Calcium signalling from the type I inositol 1,4,5-trisphosphate receptor is required at early phase of liver regeneration

BACKGROUND & AIMS

Liver regeneration is a multistage process that unfolds gradually, with different mediators acting at different stages of regeneration. Calcium (Ca(2+) ) signalling is essential for liver regeneration. In hepatocytes, Ca(2+) signalling results from the activation of inositol 1,4,5-trisphosphate receptors (InsP3 R) of which two of the three known isoforms are expressed (InsP3 R-I and InsP3 R-II). Here, we investigated the role of the InsP3 R-I-dependent Ca(2+) signals in hepatic proliferation during liver regeneration.

METHODS

Partial hepatectomy (HX) in combination with knockdown of InsP3 R-I (AdsiRNA-I) was used to evaluate the role of InsP3 R-I on liver regeneration and hepatocyte proliferation, as assessed by liver to body mass ratio, PCNA expression, immunoblots and measurements of intracellular Ca(2+) signalling.

RESULTS

AdsiRNA-I efficiently infected the liver as demonstrated by the expression of β-galactosidase throughout the liver lobules. Moreover, this construct selectively and efficiently reduced the expression of InsP3 R-I, as evaluated by immunoblots. Expression of AdsiRNA-I in liver decreased peak Ca(2+) amplitude induced by vasopressin in isolated hepatocytes 2 days after HX. Reduced InsP3 R-I expression prior to HX also delayed liver regeneration, as measured by liver to body weight ratio, and reduced hepatocyte proliferation, as evaluated by PCNA staining, at the same time point. At later stages of regeneration, control hepatocytes showed a decreased expression of InsP3 R, as well as reduced InsP3 R-mediated Ca(2+) signalling, events that did not affect liver growth.

CONCLUSION

Together, these results show that InsP3 R-I-dependent Ca(2+) signalling is an early triggering pathway required for liver regeneration.

Hepatic DNA deposition drives drug-induced liver injury and inflammation in mice

Drug-induced liver injury (DILI) is an important cause of acute liver failure, with limited therapeutic options. During DILI, oncotic necrosis with concomitant release and recognition of intracellular content amplifies liver inflammation and injury. Among these molecules, self-DNA has been widely shown to trigger inflammatory and autoimmune diseases; however, whether DNA released from damaged hepatocytes accumulates into necrotic liver and the impact of its recognition by the immune system remains elusive. Here we show that treatment with two different hepatotoxic compounds (acetaminophen and thioacetamide) caused DNA release into the hepatocyte cytoplasm, which occurred in parallel with cell death in vitro. Administration of these compounds in vivo caused massive DNA deposition within liver necrotic areas, together with an intravascular DNA coating. Using confocal intravital microscopy, we revealed that liver injury due to acetaminophen overdose led to a directional migration of neutrophils to DNA-rich areas, where they exhibit an active patrolling behavior. DNA removal by intravenous DNASE1 injection or ablation of Toll-like receptor 9 (TLR9)-mediated sensing significantly reduced systemic inflammation, liver neutrophil recruitment, and hepatotoxicity. Analysis of liver leukocytes by flow cytometry revealed that emigrated neutrophils up-regulated TLR9 expression during acetaminophen-mediated necrosis, and these cells sensed and reacted to extracellular DNA by activating the TLR9/NF-κB pathway. Likewise, adoptive transfer of wild-type neutrophils to TLR9(-/-) mice reversed the hepatoprotective phenotype otherwise observed in TLR9 absence.

CONCLUSION

Hepatic DNA accumulation is a novel feature of DILI pathogenesis. Blockage of DNA recognition by the innate immune system may constitute a promising therapeutic venue.

Succinate causes pathological cardiomyocyte hypertrophy through GPR91 activation

Background

Succinate is an intermediate of the citric acid cycle as well as an extracellular circulating molecule, whose receptor, G protein-coupled receptor-91 (GPR91), was recently identified and characterized in several tissues, including heart. Because some pathological conditions such as ischemia increase succinate blood levels, we investigated the role of this metabolite during a heart ischemic event, using human and rodent models.

Results

We found that succinate causes cardiac hypertrophy in a GPR91 dependent manner. GPR91 activation triggers the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2), the expression of calcium/calmodulin dependent protein kinase IIδ (CaMKIIδ) and the translocation of histone deacetylase 5 (HDAC5) into the cytoplasm, which are hypertrophic-signaling events. Furthermore, we found that serum levels of succinate are increased in patients with cardiac hypertrophy associated with acute and chronic ischemic diseases.

Conclusions

These results show for the first time that succinate plays an important role in cardiomyocyte hypertrophy through GPR91 activation, and extend our understanding of how ischemia can induce hypertrophic cardiomyopathy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12964-014-0078-2) contains supplementary material, which is available to authorized users.

The insulin receptor translocates to the nucleus to regulate cell proliferation in liver

Insulin's metabolic effects in the liver are widely appreciated, but insulin's ability to act as a hepatic mitogen is less well understood. Because the insulin receptor (IR) can traffic to the nucleus, and Ca(2+) signals within the nucleus regulate cell proliferation, we investigated whether insulin's mitogenic effects result from activation of Ca(2+)-signaling pathways by IRs within the nucleus. Insulin-induced increases in Ca(2+) and cell proliferation depended upon clathrin- and caveolin-dependent translocation of the IR to the nucleus, as well as upon formation of inositol 1,4,5,-trisphosphate (InsP3) in the nucleus, whereas insulin's metabolic effects did not depend on either of these events. Moreover, liver regeneration after partial hepatectomy also depended upon the formation of InsP3 in the nucleus, but not the cytosol, whereas hepatic glucose metabolism was not affected by buffering InsP3 in the nucleus.

CONCLUSION

These findings provide evidence that insulin's mitogenic effects are mediated by a subpopulation of IRs that traffic to the nucleus to locally activate InsP3 -dependent Ca(2+)-signaling pathways. The steps along this signaling pathway reveal a number of potential targets for therapeutic modulation of liver growth in health and disease.

Nucleoplasmic calcium signaling and cell proliferation: calcium signaling in the nucleus

Calcium (Ca²⁺) is an essential signal transduction element involved in the regulation of several cellular activities and it is required at various key stages of the cell cycle. Intracellular Ca²⁺ is crucial for the orderly cell cycle progression and plays a vital role in the regulation of cell proliferation. Recently, it was demonstrated by in vitro and in vivo studies that nucleoplasmic Ca²⁺ regulates cell growth. Even though the mechanism by which nuclear Ca²⁺ regulates cell proliferation is not completely understood, there are reports demonstrating that activation of tyrosine kinase receptors (RTKs) leads to translocation of RTKs to the nucleus to generate localized nuclear Ca²⁺ signaling which are believed to modulate cell proliferation. Moreover, nuclear Ca²⁺ regulates the expression of genes involved in cell growth. This review will describe the nuclear Ca²⁺ signaling machinery and its role in cell proliferation. Additionally, the potential role of nuclear Ca²⁺ as a target in cancer therapy will be discussed.

Mitochondrial calcium regulates rat liver regeneration through the modulation of apoptosis

Subcellular Ca(2+) signals control a variety of responses in the liver. For example, mitochondrial Ca(2+) (Ca(mit)(2+)) regulates apoptosis, whereas Ca(2+) in the nucleus regulates cell proliferation. Because apoptosis and cell growth can be related, we investigated whether Ca(mit)(2+) also affects liver regeneration. The Ca(2+)-buffering protein parvalbumin, which was targeted to the mitochondrial matrix and fused to green fluorescent protein, was expressed in the SKHep1 liver cell line; the vector was called parvalbumin-mitochondrial targeting sequence-green fluorescent protein (PV-MITO-GFP). This construct properly localized to and effectively buffered Ca(2+) signals in the mitochondrial matrix. Additionally, the expression of PV-MITO-GFP reduced apoptosis induced by both intrinsic and extrinsic pathways. The reduction in cell death correlated with the increased expression of antiapoptotic genes [B cell lymphoma 2 (bcl-2), myeloid cell leukemia 1, and B cell lymphoma extra large] and with the decreased expression of proapoptotic genes [p53, B cell lymphoma 2-associated X protein (bax), apoptotic peptidase activating factor 1, and caspase-6]. PV-MITO-GFP was also expressed in hepatocytes in vivo with an adenoviral delivery system. Ca(mit)(2+) buffering in hepatocytes accelerated liver regeneration after partial hepatectomy, and this effect was associated with the increased expression of bcl-2 and the decreased expression of bax.

CONCLUSION

Together, these results reveal an essential role for Ca(mit)(2+) in hepatocyte proliferation and liver regeneration, which may be mediated by the regulation of apoptosis.

Salivary parameters in Brazilian individuals with cerebral palsy who drool

BACKGROUND

Although drooling of saliva is considered abnormal in a child over 4 years of age, it has been estimated to occur in approximately in 10-37% of children with cerebral palsy.

AIM

The aim of this study was to evaluate the flow rate, pH and buffering capacity in saliva of Brazilian individuals with cerebral palsy who drool.

METHODS

Cross-sectional assessment of saliva from 139 individuals with cerebral palsy (3-16 years old) enrolled in a specialized rehabilitation centre in Sao Paulo, Brazil, divided into two groups, according to the presence (G1) or absence (G2) of drooling and controls (G3): G1 consisted of 63 individuals who drool; G2 consisted of 76 who do not drool; and G3 consisted of 47 individuals with no neurological damage of similar age and sex. Unstimulated whole saliva was collected and salivary flow rate (mL/min), initial pH and buffering capacity, by titration of saliva with a constant amount of 0.01 N HCl, were evaluated. The results from G1, G2 and G3 were compared by one-way anova and the χ(2) -test.

RESULTS

A higher percentage of severe drooling (60.3%) was observed compared with moderate (27.0%) and mild (12.7%) in the cerebral palsy individuals who drool and the prevalence of drooling was highest among children and adolescents with spastic quadriplegia. Significant reductions in salivary flow rate, initial pH, buffering capacity of whole saliva in pH range 6.0-6.9 and total buffering capacity occurred in G1 and G2 compared with G3.

CONCLUSION

All individuals with cerebral palsy present lower flow rate, pH and buffering capacity of saliva, which increases the risk of oral diseases.

In vivo astaxanthin treatment partially prevents antioxidant alterations in dental pulp from alloxan-induced diabetic rats

AIM

To evaluate the effect of astaxanthin on antioxidant parameters of dental pulp from diabetic rats. The hypothesis tested was that supplementation of diabetic rats with astaxanthin might eliminate, or at least attenuate, the defect in their antioxidative status.

METHODOLOGY

Wistar rats (n=32) were divided into four groups: untreated control, treated control, untreated diabetic and treated diabetic rats. A prophylactic dose of astaxanthin (20 mg kg(-1) body weight) was administered daily by gavage for 30 days. On day 23, diabetes was induced by injection of alloxan (60 mg kg(-1) body weight). After 7 days of diabetes induction, the rats were killed, and pulp tissue from incisor teeth removed. Superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx) and reductase activities were determined. Data were compared by anova and the Newman-Keuls test (P<0.05).

RESULTS

Diabetes caused a reduction in SOD, GPx and reductase activity in dental pulp tissue. Astaxanthin had no effect on SOD and catalase activities; however, it stimulated GPx in control and diabetic rats.

CONCLUSIONS

Diabetes altered the antioxidant system in dental pulp tissue; astaxanthin partially improved the diabetic complications.

Highly efficient siRNA delivery system into human and murine cells using single-wall carbon nanotubes

Development of RNA interference (RNAi) technology utilizing short interfering RNA sequences (siRNA) has focused on creating methods for delivering siRNAs to cells and for enhancing siRNA stability in vitro and in vivo. Here, we describe a novel approach for siRNA cellular delivery using siRNA coiling into carboxyl-functionalized single-wall carbon nanotubes (SWCNTs). The CNT-siRNA delivery system successfully demonstrates nonspecific toxicity and transfection efficiency greater than 95%. This approach offers the potential for siRNA delivery into different types of cells, including hard-to-transfect cells, such as neuronal cells and cardiomyocytes. We also tested the CNT-siRNA system in a non-metastatic human hepatocellular carcinoma cell line (SKHep1). In all types of cells used in this work the CNT-siRNA delivery system showed high efficiency and apparent no side effects for various in vitro applications.

Succinate modulates Ca(2+) transient and cardiomyocyte viability through PKA-dependent pathway

GPR91 is an orphan G-protein-coupled receptor (GPCR) that has been characterized as a receptor for succinate, a citric acid cycle intermediate, in several tissues. In the heart, the role of succinate is unknown. We now report that rat ventricular cardiomyocytes express GPR91. We found that succinate, through GPR91, increases the amplitude and the rate of decline of global Ca(2+) transient, by increasing the phosphorylation levels of ryanodine receptor and phospholamban, two well known Ca(2+) handling proteins. The effects of succinate on Ca(2+) transient were abolished by pre-treatment with adenylyl cyclase and cAMP-dependent protein kinase (PKA) inhibitors. Direct PKA activation by succinate was further confirmed using a FRET-based A-kinase activity reporter. Additionally, succinate decreases cardiomyocyte viability through a caspase-3 activation pathway, effect also prevented by PKA inhibition. Taken together, these observations show that succinate acts as a signaling molecule in cardiomyocytes, modulating global Ca(2+) transient and cell viability through a PKA-dependent pathway.

Assessment of the potential genotoxic risk of medicinal Tamarindus indica fruit pulp extract using in vivo assays

Tamarindus indica has been used in folk medicine as an antidiabetic, a digestive aid, and a carminative, among other uses. Currently, there is no information in the toxicology literature concerning the safety of T. indica extract. We evaluated the clastogenic and/or genotoxic potential of fruit pulp extract of this plant in vivo in peripheral blood and liver cells of Wistar rats, using the comet assay, and in bone marrow cells of Swiss mice, using the micronucleus test. The extract was administered by gavage at doses of 1000, 1500 and 2000 mg/kg body weight. Peripheral blood and liver cells from Wistar rats were collected 24 h after treatment, for the comet assay. The micronucleus test was carried out in bone marrow cells from Swiss mice collected 24 h after treatment. The extract made with T. indica was devoid of clastogenic and genotoxic activities in the cells of the rodents, when administered orally at these three acute doses.

Effects of extracellular calcium concentration on the glutamate release by bioactive glass (BG60S) preincubated osteoblasts

Glutamate released by osteoblasts sharing similarities with its role in neuronal transmission is a very new scientific concept which actually changed the understanding of bone physiology. Since glutamate release is a calcium (Ca(2+))-dependent process and considering that we have previously demonstrated that the dissolution of bioactive glass with 60% of silicon (BG60S) can alter osteoblast Ca(2+)-signaling machinery, we investigated whether BG60S induces glutamate secretion in osteoblasts and whether it requires an increase in intracellular Ca(2+). Here we showed that the extracellular Ca(2+) increase due to BG60S dissolution leads to an intracellular Ca(2+) increase in the osteoblast, through the activation of an inositol 1,4,5-triphosphate receptor (InsP(3)R) and a ryanodine receptor (RyR). Additionally, we also demonstrated that glutamate released by osteoblasts can be profoundly altered by BG60S. The modulation of osteoblast glutamate released by the extracellular Ca(2+) concentration opens a new window in the field of tissue engineering, since many biomaterials used for bone repair are able to increase the extracellular Ca(2+) concentration due to their dissolution products.

Left atrial shortening fraction in fetuses with and without myocardial hypertrophy in diabetic pregnancies

OBJECTIVE

To test the hypothesis that, in diabetic pregnancies, left atrial shortening fraction (LASF) is decreased in fetuses with myocardial hypertrophy, compared to those without hypertrophy and to fetuses of non-diabetic mothers.

METHODS

Fetal echocardiography was performed in women with pre-existing or gestational diabetes and in non-diabetic controls between 25 weeks' gestation and term. LASF was calculated using the formula: (end-systolic diameter-end-diastolic diameter)/end-systolic diameter, and data were compared between diabetic women with and without fetal myocardial hypertrophy and controls.

RESULTS

The study population comprised 53 diabetic women and 45 controls. Out of the 53 fetuses of diabetic women, 14 had myocardial hypertrophy and 39 had normal septal thickness. Gestational age at the time of examination did not differ significantly between the control group and the two diabetic subgroups (P = 0.57). Fetuses with myocardial hypertrophy presented a mean ( +/- SD) LASF of 0.32 +/- 0.11, those without myocardial hypertrophy 0.46 +/- 0.12, and those of normal mothers 0.53 +/- 0.09 (P < 0.001). A significant inverse linear correlation was observed between LASF and septal thickness (r = - 0.51, P < 0.001).

CONCLUSIONS

In diabetic pregnancies, LASF is lower in fetuses with myocardial hypertrophy than it is in those without hypertrophy and in fetuses of non-diabetic women, suggesting that LASF could be a useful alternative parameter in the assessment of fetal diastolic function.

Nuclear calcium signaling: a cell within a cell

Calcium (Ca2+) is a versatile second messenger that regulates a wide range of cellular functions. Although it is not established how a single second messenger coordinates diverse effects within a cell, there is increasing evidence that the spatial patterns of Ca2+ signals may determine their specificity. Ca2+ signaling patterns can vary in different regions of the cell and Ca2+ signals in nuclear and cytoplasmic compartments have been reported to occur independently. No general paradigm has been established yet to explain whether, how, or when Ca2+ signals are initiated within the nucleus or their function. Here we highlight that receptor tyrosine kinases rapidly translocate to the nucleus. Ca2+ signals that are induced by growth factors result from phosphatidylinositol 4,5-bisphosphate hydrolysis and inositol 1,4,5-trisphosphate formation within the nucleus rather than within the cytoplasm. This novel signaling mechanism may be responsible for growth factor effects on cell proliferation.

Insulin induces calcium signals in the nucleus of rat hepatocytes

Insulin is an hepatic mitogen that promotes liver regeneration. Actions of insulin are mediated by the insulin receptor, which is a receptor tyrosine kinase. It is currently thought that signaling via the insulin receptor occurs at the plasma membrane, where it binds to insulin. Here we report that insulin induces calcium oscillations in isolated rat hepatocytes, and that these calcium signals depend upon activation of phospholipase C and the inositol 1,4,5-trisphosphate receptor, but not upon extracellular calcium. Furthermore, insulin-induced calcium signals occur in the nucleus, and are temporally associated with selective depletion of nuclear phosphatidylinositol bisphosphate and translocation of the insulin receptor to the nucleus. These findings suggest that the insulin receptor translocates to the nucleus to initiate nuclear, inositol 1,4,5-trisphosphate-mediated calcium signals in rat hepatocytes. This novel signaling mechanism may be responsible for insulin's effects on liver growth and regeneration.

c-Jun Inhibits Thapsigargin-Induced ER Stress Through Up-Regulation of DSCR1/Adapt78

The endoplasmic reticulum (ER) is exquisitely sensitive to changes in its internal environment. Various conditions, collectively termed “ER stress”, can perturb ER function, leading to the activation of a complex response known as the unfolded protein response (UPR). Although c-Jun N-terminal kinase (JNK) activation is nearly always associated with cell death by various stimuli, the functional role of JNK in ER stress-induced cell death remains unclear. JNK regulates gene expression through the phosphorylation and activation of transcription factors, such as c-Jun. Here, we investigated the role of c-Jun in the regulation of ER stress-related genes. c-Jun expression levels determined the response of mouse fibroblasts to ER stress induced by thapsigargin (TG, an inhibitor of sarco/endoplasmic reticulum Ca2+ ATPase). c-jun−/− mouse fibroblast cells were more sensitive to TG-induced cell death compared to wild-type mouse fibroblasts, while reconstitution of c-Jun expression in c-jun−/− cells (c-Jun Re) enhanced resistance to TG-induced cell death. The expression levels of ER chaperones Grp78 and Gadd153 induced by TG were lower in c-Jun Re than in c-jun−/− cells. Moreover, TG treatment significantly increased calcineurin activity in c-jun−/− cells, but not in c-Jun Re cells. In c-Jun Re cells, TG induced the expression of Adapt78, also known as the Down syndrome critical region 1 (DSCR1), which is known to block calcineurin activity. Taken together, our findings suggest that c-Jun, a transcription factor downstream of the JNK signaling pathway, up-regulates Adapt78 expression in response to TG-induced ER stress and contributes to protection against TG-induced cell death.

Nuclear Ca2+ regulates cardiomyocyte function

In the heart, cytosolic Ca(2+) signals are well-characterized events that participate in the activation of cell contraction. In contrast, nuclear Ca(2+) contribution to cardiomyocyte function remains elusive. Here, we examined functional consequences of buffering nuclear Ca(2+) in neonatal cardiomyocytes. We report that cardiomyocytes contain a nucleoplasmic reticulum, which expresses both ryanodine receptor (RyR) and inositol 1,4,5-trisphosphate receptor (InsP(3)R), providing a possible way for active regulation of nuclear Ca(2+). Adenovirus constructs encoding the Ca(2+) buffer protein parvalbumin were targeted to the nucleus with a nuclear localization signal (Ad-PV-NLS) or to the cytoplasm with a nuclear exclusion signal (Ad-PV-NES). A decrease in the amplitude of global Ca(2+) transients and RyR-II expression, as well as an increase in cell beating rate were observed in Ad-PV-NES and Ad-PV-NLS cells. When nuclear Ca(2+) buffering was imposed nuclear enlargement, increased calcineurin expression, NFAT translocation to the nucleus and subcellular redistribution of atrial natriuretic peptide were observed. Furthermore, prolongation of action potential duration occurred in adult ventricular myocytes. These results suggest that nuclear Ca(2+) levels underlie the regulation of specific protein targets and thereby modulate cardiomyocyte function. The local nuclear Ca(2+) signaling and the structures that control it constitute a novel regulatory motif in the heart.

c-Met must translocate to the nucleus to initiate calcium signals

Hepatocyte growth factor (HGF) is important for cell proliferation, differentiation, and related activities. HGF acts through its receptor c-Met, which activates downstream signaling pathways. HGF binds to c-Met at the plasma membrane, where it is generally believed that c-Met signaling is initiated. Here we report that c-Met rapidly translocates to the nucleus upon stimulation with HGF. Ca(2+) signals that are induced by HGF result from phosphatidylinositol 4,5-bisphosphate hydrolysis and inositol 1,4,5-trisphosphate formation within the nucleus rather than within the cytoplasm. Translocation of c-Met to the nucleus depends upon the adaptor protein Gab1 and importin beta1, and formation of Ca(2+) signals in turn depends upon this translocation. HGF may exert its particular effects on cells because it bypasses signaling pathways in the cytoplasm to directly activate signaling pathways in the nucleus.

Succinate is a paracrine signal for liver damage

BACKGROUND/AIMS

A G-protein-coupled succinate receptor has recently been identified in several tissues, including the liver. The objectives of this work were to determine the hepatic cell types that express this receptor and to determine its physiological role.

METHODS

Expression and distribution of the succinate receptor was determined by RT-PCR and confocal immunofluorescence. Biochemical assays were used to measure succinate and cAMP. Cytosolic Ca2+ was monitored in single cells by time-lapse imaging. Western blot was used to study the effect of succinate on activation of hepatic stellate cells.

RESULTS

The succinate receptor was expressed in quiescent hepatic stellate cells, and expression decreased with activation. Ischemia induced release of succinate in isolated perfused livers. In contrast to what is observed in cell expression systems, succinate did not inhibit cAMP production or increase cytosolic Ca2+ in primary hepatic stellate cells. However, succinate accelerated stellate cell activation.

CONCLUSIONS

Hepatic stellate cells express the succinate receptor. Succinate may behave as a paracrine signal by which ischemic hepatocytes trigger stellate cell activation.

Biocompatibility evaluation of hydroxyapatite/collagen nanocomposites doped with Zn+2

In this work, novel composites based on calcium phosphates (CaP)/collagen (COL) doped with Zn(+2) have been synthesized. They were characterized by SEM coupled to EDS microprobe in order to evaluate their morphology and chemical composition, respectively. The biocompatibility of these synthetic CaP/COL nanocomposites doped and undoped with Zn(+2) was investigated through osteoblast cell culture assay. Calcium phosphates were produced via aqueous precipitation routes where two different phases were obtained, hydroxyapatite (HAP) and biphasic hydroxyapatite-betatricalcium phosphate (HAPbetaTCP). In the sequence, the type-I collagen (COL) was added to the inorganic phase based on calcium phosphate and the mixture was blended until a homogenous composite was obtained. Zn(+2) aqueous solution (1.0 wt%) was used as the doping reagent. The cell viability and the alkaline phosphatase production of osteoblasts in the presence of the composites were evaluated and compared to control osteoblasts. Also, the biocompatibility of the composite was investigated through cell morphological analysis using optical microscopy of osteoblasts. All experiments were performed in triplicates (n = 3) from three different experiments. They were analyzed by variance test (ANOVA) and Bonferroni's post-test with differences statistically significant at p < 0.05. The results showed that the CaP/COL composites doped and undoped with Zn(+2) did not present alterations in cell morphology in 72 h and had similar cell viability and alkaline phosphatase activity to the control. All the tested CaP/COL composites showed adequate biological properties with the potential to be used in bone tissue replacement applications.

3D chitosan-gelatin-chondroitin porous scaffold improves osteogenic differentiation of mesenchymal stem cells

A porous 3D scaffold was developed to support and enhance the differentiation process of mesenchymal stem cells (MSC) into osteoblasts in vitro. The 3D scaffold was made with chitosan, gelatin and chondroitin and it was crosslinked by EDAC. The scaffold physicochemical properties were evaluated. SEM revealed the high porosity and interconnection of pores in the scaffold; rheological measurements show that the scaffold exhibits a characteristic behavior of strong gels. The elastic modulus found in compressive tests of the crosslinked scaffold was about 50 times higher than the non-crosslinked one. After 21 days, the 3D matrix submitted to hydrolytic degradation loses above 40% of its weight. MSC were collected from rat bone marrow and seeded in chitosan-gelatin-chondroitin 3D scaffolds and in 2D culture plates as well. MSC were differentiated into osteoblasts for 21 days. Cell proliferation and alkaline phosphatase activity were followed weekly during the osteogenic process. The osteogenic differentiation of MSC was improved in 3D culture as shown by MTT assay and alkaline phosphatase activity. On the 21st day, bone markers, osteopontin and osteocalcin, were detected by the PCR analysis. This study shows that the chitosan-gelatin-chondroitin 3D structure provides a good environment for the osteogenic process and enhances cellular proliferation.

Nucleoplasmic calcium is required for cell proliferation

Ca(2+) signals regulate cell proliferation, but the spatial and temporal specificity of these signals is unknown. Here we use selective buffers of nucleoplasmic or cytoplasmic Ca(2+) to determine that cell proliferation depends upon Ca(2+) signals within the nucleus rather than in the cytoplasm. Nuclear Ca(2+) signals stimulate cell growth rather than inhibit apoptosis and specifically permit cells to advance through early prophase. Selective buffering of nuclear but not cytoplasmic Ca(2+) signals also impairs growth of tumors in vivo. These findings reveal a major physiological and potential pathophysiological role for nucleoplasmic Ca(2+) signals and suggest that this information can be used to design novel therapeutic strategies to regulate conditions of abnormal cell growth.

The spatial distribution of inositol 1,4,5-trisphosphate receptor isoforms shapes Ca2+ waves

Cytosolic Ca(2+) is a versatile second messenger that can regulate multiple cellular processes simultaneously. This is accomplished in part through Ca(2+) waves and other spatial patterns of Ca(2+) signals. To investigate the mechanism responsible for the formation of Ca(2+) waves, we examined the role of inositol 1,4,5-trisphosphate receptor (InsP3R) isoforms in Ca(2+) wave formation. Ca(2+) signals were examined in hepatocytes, which express the type I and II InsP3R in a polarized fashion, and in AR4-2J cells, a nonpolarized cell line that expresses type I and II InsP3R in a ratio similar to what is found in hepatocytes but homogeneously throughout the cell. Expression of type I or II InsP3R was selectively suppressed by isoform-specific DNA antisense in an adenoviral delivery system, which was delivered to AR4-2J cells in culture and to hepatocytes in vivo. Loss of either isoform inhibited Ca(2+) signals to a similar extent in AR4-2J cells. In contrast, loss of the basolateral type I InsP3R decreased the sensitivity of hepatocytes to vasopressin but had little effect on the initiation or spread of Ca(2+) waves across hepatocytes. Loss of the apical type II isoform caused an even greater decrease in the sensitivity of hepatocytes to vasopressin and resulted in Ca(2+) waves that were much slower and delayed in onset. These findings provide evidence that the apical concentration of type II InsP3Rs is essential for the formation of Ca(2+) waves in hepatocytes. The subcellular distribution of InsP3R isoforms may critically determine the repertoire of spatial patterns of Ca(2+) signals.

BG60S dissolution interferes with osteoblast calcium signals

We investigated the influence of extracellular calcium concentration, caused by the dissolution of a bioactive glass with 60% of silicon (BG60S), on intracellular calcium (Ca(i) (2 +)) signals and expression of inositol 1, 4, 5-triphosphate receptors (InsP(3)R) in primary culture of osteoblasts. We found that BG60S caused an increase in Ca(i) (2 +) signals in this cell type. Additionally, osteoblasts pre-incubated in the presence of BG60S showed an increase in Ca(i) (2 +) when cells were stimulated with vasopressin. On the other hand, a decrease in Ca(i) (2 +) signals were observed in osteoblasts pre-treated with BG60S and stimulated with KCl. We furher found that in osteoblasts, the type I InsP(3)R is preferentially distributed in the nucleus while the type II InsP(3)R in the cytoplasm. Preincubation of osteoblasts with BG60S altered the receptor expression level, increasing the type I InsP(3)R in the nucleus and decreasing type II InsP(3)R in the cytosol. Together, our results showed that in osteoblasts, BG60S increased Ca(i) (2 +)signals and altered Ca(i) (2 +) machinery.

Interleukin-10 and Tumor Necrosis Factor–α Single Nucleotide Gene Polymorphism Frequency in Paracoccidioidomycosis

Allelic variants of cytokine genes seem to be involved in mechanisms of resistance or susceptibility to several diseases. The aim of this study was to investigate the frequency of genotypes with the tumor necrosis factor-alpha TNF-alpha gene polymorphism G/A at position -308 and the IL-10 gene polymorphism G/A at position -1082, and to verify a possible association of these polymorphisms with paracoccidioidomycosis (PCM) caused by Paracoccidioides brasiliensis. Genotyping was performed by allele-specific polymerase chain reaction (ASPCR) and restriction fragment length polymorphism (RFLP) on genomic DNA isolated of granulocytes from 54 PCM patients and 31 noninfected individuals. The analysis of SNP at position -1082 IL-10 showed a high frequency of GA genotype in both patients and controls (51% and 55%, respectively), while the allelic frequency showed 54% of G allele in the patients and 66% of A allele in the controls. The GG genotype was more frequent in patients (85%) and controls (68%) when we analyze the SNP at position -308 of TNF-alpha gene. Otherwise, 91% of PCM patients and 84% of noninfected individuals carried the G allele in -308 TNF-alpha SNP. Stimulation of cells from individuals with PCM phenotyped as A+ (GA or AA genotypes) presented elevation of TNF-alpha producing cells when compared with IL-10-producer cells. These findings reinforce the critical role of IL-10 and TNF-alpha in the paracoccidioidomycosis and can strongly suggest that the genetic screening of the -308G/A and -1082G/A polymorphisms may be a valid tool for identification of subjects needing a more appropriate therapy.

Calcium signaling in the nucleus

Cytosolic Ca(2+) is a versatile secondary messenger that regulates a wide range of cellular activities. In the past decade, evidence has accumulated that free Ca(2+) within the nucleus also plays an important messenger function. Here we review the mechanisms and effects of Ca(2+) signals within the nucleus. In particular, evidence is reviewed that the nucleus contains the machinery necessary for production of inositol 1,4,5-trisphosphate and for inositol 1,4,5-trisphosphate receptor-mediated Ca(2+) release. The role of Ca(2+) signals within the nucleus is discussed including regulation of such critical cell functions as gene expression, activation of kinases, and permeability of nuclear pores.

Calcium release from ryanodine receptors in the nucleoplasmic reticulum

Ca(2+) signals control DNA synthesis and repair, gene transcription, and other cell functions that occur within the nucleus. The nuclear envelope can store Ca(2+) and release it into the nucleus via either the inositol 1,4,5-trisphosphate receptor (InsP3R) or the ryanodine receptor (RyR). Furthermore, many cell types have a reticular network within their nuclei and InsP3Rs on this nucleoplasmic reticulum permit local subnuclear control of Ca(2+) signals and Ca(2+)-dependent intranuclear events. However, it is unknown whether RyR similarly is expressed on the nucleoplasmic reticulum and can control subnuclear Ca(2+) signals. Here we report that the type 1 RyR is expressed on intranuclear extensions of the sarcoplasmic reticulum of C2C12 cells, a skeletal muscle derived cell line. In addition, two-photon photorelease of caged Ca(2+) in the region of the nucleoplasmic reticulum evoked Ca(2+)-induced Ca(2+) release (CICR) within the nucleus, which could be suppressed by the RyR inhibitor dantrolene. These results show that intranuclear extensions of the nuclear envelope have functional RyR and provide a possible mechanism whereby cells expressing RyR can regulate Ca(2+) signals in discrete regions within the nucleus.

Membrane and extracellular antigens of Paracoccidioides brasiliensis (Mexo): Identification of a 28-kDa protein suitable for immunodiagnosis of paracoccidioidomycosis

In this work, we analyzed serological responses of paracoccidioidomycosis (PCM) patients to membrane and extracellular antigens (Mexo) of Paracoccidioides brasiliensis by ELISA, immunoblot technique and immunofluorescence assays to identify a specific antigen profile. Among 140 PCM serum samples analyzed, a homogeneous IgG response to Mexo was observed. The specificity of this antigen was 96.6% in relation to control sera and 81.2% to sera from patients with diverse infections. Patients undergoing treatment for more than 1 year showed a reduced antibody response against Mexo. These results suggest that the presence of anti-Mexo antibodies might be an indicator of active disease. A protein from Mexo with a molecular weight of 28 kDa (Pb28) was the most specific antigen in humoral immune responses to PCM, since it reacted with 100% of patient sera and did not react with heterologous serum samples tested. This protein was purified by molecular filtration chromatography in FPLC system and, when tested by immunoblotting, it maintained its reactivity and specificity of 100% with PCM sera. The Pb28 N-terminal amino acid sequence comparison analysis in the non-redundant GenBank database at NCBI revealed no significant homology to known PCM proteins or to other fungal proteins of known function. Since the 28-kDa protein of P. brasiliensis seems to be specific for PCM, it can be used as an alternative antigen in immunoblotting diagnostic methods.

Identification of immunogenic proteins from Paracoccidioides brasiliensis antigenic fractions F0, FII and FIII

Paracoccidioides brasiliensis causes a chronic granulomatous mycosis prevalent in South America, and cell-mediated immunity is the principal mode of protection against this fungal infection. In this context, one of the strategies to discover proteins that are target of an effective immune response against P. brasiliensis is the partial sequencing of cDNA from an expression library previously screened with immunoglobulins (Ig) to generate antigen sequence tags (AST). In the present work, a P. brasiliensis yeast cDNA expression library was screened with affinity chromatography-purified IgG from rabbit sera immunized with P. brasiliensis antigenic fractions (F0, FII or FIII) or from paracoccidioidomycosis (PCM) patient sera by indirect ELISA. From 119 clones selected by the immunoscreening procedure, 40% were recognized by IgG from PCM patients, 25% were recognized by anti-F0, 8% were selected by anti-FII and 11% recognized by FIII specific antibodies. The remaining clones presented cross-reaction to all anti-sera tested. The AST homologies with previously reported sequences in the nonredundant GenBank at NCBI revealed high significant homology to fungal proteins of known function. One of them matched calcineurin B of Neurospora crassa with 35% identity and 55% similarity in amino acid sequence. We also identified an AST homologous to a Kinesin like protein from Ustilagus maydis and other fungi with 86% identity and 91% similarity. On the other hand, the vast majority of selected cDNA clones are new genes and represent 60% of the total. Prediction of transmembrane regions with the prediction transmembrane protein topology with a hidden markov model (TMHMM) revealed consensus sequences representing structural membrane segments in 28 encoded proteins.

The type III inositol 1,4,5-trisphosphate receptor preferentially transmits apoptotic Ca2+ signals into mitochondria

There are three isoforms of the inositol 1,4,5- trisphosphate receptor (InsP(3)R), each of which has a distinct effect on Ca(2+) signaling. However, it is not known whether each isoform similarly plays a distinct role in the activation of Ca(2+)-mediated events. To investigate this question, we examined the effects of each InsP(3)R isoform on transmission of Ca(2+) signals to mitochondria and induction of apoptosis. Each isoform was selectively silenced using isoform-specific small interfering RNA in Chinese hamster ovary cells, which express all three InsP(3)R isoforms. ATP-induced cytosolic Ca(2+) signaling patterns were altered, regardless of which isoform was silenced, but in a different fashion depending on the isoform. ATP also induced Ca(2+) signals in mitochondria, which were inhibited more effectively by silencing the type III InsP(3)R than by silencing either the type I or type II isoform. The type III isoform also co-localized most strongly with mitochondria. When apoptosis was induced by activation of either the extrinsic or intrinsic apoptotic pathway, induction was reduced most effectively by silencing the type III InsP(3)R. These findings provide evidence that the type III isoform of the InsP(3)R plays a special role in induction of apoptosis by preferentially transmitting Ca(2+) signals into mitochondria.

Primary osteoblast cell response to sol-gel derived bioactive glass foams

Bioactive glass macroporous structures were developed in this work to be used as scaffolds for bone tissue engineering applications. A sol-gel route was used to obtain glass foams with the introduction of a gas phase in the solution and by vigorous agitation of the sol-gel solution that contains a foam agent. Stable and homogeneous foams were formed near the gelation point, which were than dried and heat-treated. Macroporous structures with interconnected pores of up to 500 mu m, porosity as high as 88% and specific surface area of 92 m(2)/g were obtained. The porous glasses were tested in osteoblast cultures to evaluate adhesion, proliferation, collagen and alkaline phosphatase production. Osteoblast proliferation was higher in the presence of the foams as well as was the collagen secretion, when compared to control. The alkaline phosphatase production was not altered. Viable osteoblasts could be seen inside the foams, suggesting that the produced porous glass foams are a promising materials for bone repair, since it provides a good environment for the adhesion and proliferation of osteoblasts.

GM-CSF and TNF-alpha synergize to increase in vitro granuloma size of PBMC from humans induced by Schistosoma mansoni recombinant 28-kDa GST

The 28-kDa Glutathione S-transferase of Schistosoma mansoni (Sm28 GST) was described as a protective antigen capable of reducing female fecundity and the number of eggs in mice hepatic tissues. The role of GM-CSF and TNF-alpha in the in vitro granuloma reaction of peripheral blood mononuclear cells (PBMC) from chronic intestinal schistosomiasis patients before and after chemotherapy treatment to S. mansoni recombinant Sm28 GST was evaluated. Treatment of PBMC with recombinant Sm28 GST caused a significant increase in granuloma formation when compared to SEA or SWAP. Contrary to SEA or SWAP, Sm28 GST was not capable of inducing significant cellular proliferation. Moreover, recombinant Sm28 GST promoted a significant elevation in GM-CSF and TNF-alpha levels. However, we did not detect any significant IL-10 production. When Sm28 GST was applied in the presence of anti-GM-CSF or anti-TNF-alpha antibodies in cultures, we observed a significant decrease in granuloma size. Indeed, our results demonstrated that Sm28 GST was capable of promoting high in vitro granuloma index, and this event was associated with the balance of GM-CSF and TNF-alpha. These evidences suggest a role for GM-CSF as a major mediator in increasing granuloma reaction in human schistosomiasis. This event may contribute to exacerbate the pathology resulting from egg deposition in host tissues.

Vasopressinergic hypothalamic neurons are recruited during the audiogenic seizure of WARs

The Wistar Audiogenic Rat (WAR) is a genetic model of reflex epilepsy with seizures induced by high-intensity sound stimulation (120 dB SPL). In spite of the known neural substrates involved in WAR seizure phenotype, neuroendocrine hypothalamic neurons were never investigated. In this work, AVP immunohistochemistry in the hypothalamus and radioimmunoassay (RIA) in plasma and in hypothalamic and hypophysial tissues were performed on both controls and WARs in order to evaluate the dynamics of AVP release due to seizure induction. Susceptible animals (WARs) displayed at least tonic-clonic convulsions followed by clonic spasms, while resistant Wistar rats (R) had no convulsive behavior. Animals were sacrificed at 3 instances: basal condition (without stimulus) and at 3 and 10 min after sound stimulation. For the immunohistochemistry AVP study, brains were harvested and processed by the avidin-biotin-peroxidase detection method. Optic densitometry was used for quantifying AVP labeling in supraoptic (SON) and paraventricular (PVN) hypothalamic nuclei. SON presented higher densitometry levels (%D--relative to background) for both WARs and R when compared to PVN. Nevertheless, both nuclei presented a marked decrease, referenced to basal levels, in %D for WARs at 3 min (approximately 35%) against a discrete change for R (approximately 90%). RIA results were significantly higher in the hypophysis of WARs when compared to R rats, at 3 min. Also, at 3 min, plasma AVP in WARs (89.32 +/- 24.81 pg/mL) were higher than in R (12.01 +/- 2.39 pg/mL). We conclude, based on the AVP releasing profiles, that vasopressinergic hypothalamic neurons are recruited during the audiogenic seizure of WARs.

Detection of IgG binding to Schistosoma mansoni recombinant protein RP26 is a sensitive and specific method for acute schistosomiasis diagnosis

We recently described the first recombinant Schistosoma mansoni protein RP26, which was capable of acute infection diagnosis. The aim of the present work was to further characterize the RP26 diagnostic properties in immunoblot and enzyme-linked immunosorbent (ELISA) assays. Testing sera from uninfected donors and sera from patients with acute or chronic Schistosoma infection by Western blot immunoassay revealed 100% specificity and 100% sensitivity for acute infection identification. Sera from uninfected, acute, and chronic schistosomiasis were also probed for IgG, IgG4, IgA, and IgM reactivity to RP26 plus soluble egg antigens (SEA) in ELISA. The mean IgG reactivity to RP26 by sera from acute schistosomiasis patients was significantly higher than the chronic ones. The IgG4, IgA, and IgM reactivities to RP26 were low and similar in both infected groups. The mean IgA and IgM reactivities to SEA were significantly higher in the group of acute compared to chronic group, whereas mean IgG4 reactivity was higher in chronic group. To estimate the specificity of Schistosoma infection diagnosis sera from patients infected with other different parasites were tested to detect IgG reactivity to RP26 and IgA and IgM reactivity to SEA. For IgA against SEA detection, 72% of sera were positive and 48% of sera were positive for IgM detection. Based on these results we can suggest that detection of sera IgG binding to RP26 is a sensitive and specific method for acute schistosomiasis diagnosis. Therefore, RP26 is a candidate for immunodiagnostic kit development.

Modulation of CD28 and CD86 Expression in Patients with Paracoccidioidomycosis in Different Periods of Treatment

Paracoccidioides brasiliensis, a thermo-dimorphic fungus, is the ethiologic agent of paracoccidioidomycosis (PCM). The recidive is the greatest obstacle of this disease, because the yeast usually returns after the long treatment period. In the present work, we have investigated the cellular immune response of cells from peripheral blood drawn from patients with different duration of PCM. The classification of patients ranged from nontreated to those with long-standing disease over 5 years. Unstimulated as well as cells stimulated with phytohemaglutinin or two different antigen preparations, secreted (MEXO) or somatic (PbAg) of P. brasiliensis, were characterized. We found that cells from patients with disease proliferate considerably upon stimulation with the antigen preparations and that cells from patients with disease of long duration does not proliferate that vigorously as from patients with more recent diagnosis. Both interferon (IFN)-gamma and interleukin (IL)-4 appear to be increased in patients, but IFN-gamma tended to increase upon treatment while IL-4-secretion decreased. With respect to CD28 and CD86, we found that the subset of CD28 positive CD8 cells are decreased in all stages of the disease as compared to control individuals. A subset of CD86 positive CD19 cells appeared to be considerably increased compared to the controls. Indeed, our results demonstrated that the treatment of PCM patients promoted a regulation of IFN-gamma, IL-4 levels and CD28, CD86 expression bringing new insight to the cellular immune response in PCM.

The effect of ionic products from bioactive glass dissolution on osteoblast proliferation and collagen production

Bioactive ceramics developed during the past few decades have interesting properties from the biological standpoint, but their effects on cellular events remain partially unknown. In the current work, we investigated cellular viability, proliferation, morphology changes and metabolic activity of rat primary culture osteoblasts in contact with the ionic products from the dissolution of a bioactive glass with 60% of silica (BG60S) and a biphasic calcium phosphate (BCP). We observed that although osteoblasts cultured with BG60S showed vacuole formation, cell viability was increased when compared to BCP and control. The vacuole formation was not due to the presence of high calcium concentration in the ionic products from the dissolution of BG60S and was not related to nitric oxide production from the osteoblasts. We did find that high silicon concentration could induce cellular vacuole formation. Additionally, energy dispersive spectroscopy analysis indicated that vacuole contained 75% more silicon than other regions in the cell outside the vacuole. We further found that collagen production was higher in osteoblast cultured in the presence of BG60S compared to BCP and control, while alkaline phosphatase production was similar among cells incubated with BG60S, BCP and control. Together, our results indicate that osteoblast vacuole formation was due to high silicon contents in the dissolution of BG60S and we can suggest that despite the vacuole formation, there is no significant alteration in the bioceramic cell interaction.

Endotoxin unmasks the role of gap junctions in the liver

Gap junctions are thought to be necessary for proper tissue function. However, no clear hepatic phenotype has been described in patients lacking connexin 32 (Cx32), the principal gap junction in liver. To determine the physiological role of Cx32 in liver, we compared the response of wild type and Cx32-deficient mice to endotoxin, since this stress increases serum levels of hormones that bind to receptors that are asymmetrically distributed across the hepatic lobule. In hepatocyte couplets isolated from wild type mice, most hepatocytes could transfer microinjected dye to their neighbor even after treatment with endotoxin. Dye transfer was not observed in Cx32-deficient couplets. Treatment of hepatocyte couplets from wild type mice with vasopressin induced calcium (Ca(2+)) waves that crossed the couplets in a concentration-dependent fashion, but the delay in transmission was markedly prolonged at all concentrations in Cx32-deficient couplets. Expression of the vasopressin receptor and the inositol 1,4,5-trisphosphate receptor was not decreased by endotoxin or in Cx32-deficient couplets. Finally, endotoxin caused transient hypoglycemia and cholestasis in wild type animals, but hypoglycemia was slightly prolonged and cholestasis was much worse in Cx32-deficient mice treated with endotoxin. The hepatic response to endotoxin is markedly impaired in the absence of Cx32. Thus, an important role of gap junctions in the liver is to assure integrated and uniform tissue response in times of stress.

Schistosoma mansoni PIII antigen modulates in vitro granuloma formation by regulating CD28, CTLA-4, and CD86 expression in humans

We investigated the in vitro responses of peripheral blood mononuclear cells (PBMC) from intestinal chronic schistosomiasis patients to PIII, a multivalent antigen prepared from Schistosoma mansoni adult worm. PIII decreased cellular proliferation and granulomatous reaction. Moreover, induced the reduction of IFN-gamma levels and increased IL-10 production. To better understand the mechanism through which the observed suppression occurs, the present study focused on the phenotypic pattern displayed by PBMC treated with PIII in an in vitro granuloma assay. Expression of the surface markers CD28, CTLA-4 and CD86 by lymphocytes and monocytes were analyzed by flow cytometry. Our results demonstrated a significant decrease of CD28+CD4+ and CD28+CD8+ T-cell percentage stimulated by PIII compared to its non-infected counterparts. This suppressive effect was related to a significant increase in the percentage of T-cells expressing CTLA-4. PIII also promoted a significant increase in the percentage of cells expressing CD86. Indeed, our results demonstrated that PIII was capable of modulating in vitro granuloma reaction, and this event was related to the balance of IL-10, IFN-gamma and CD28, CTLA-4, CD86 bringing new insight to the immunoregulation of granulomatous hypersensitivity in human schistosomiasis.