Purinergic signaling is required for fluid shear stress-induced NF-κB translocation in osteoblasts

Differential contribution of THIK-1 K+ channels and P2X7 receptors to ATP-mediated neuroinflammation by human microglia

Neuroinflammation is highly influenced by microglia, particularly through activation of the NLRP3 inflammasome and subsequent release of IL-1β. Extracellular ATP is a strong activator of NLRP3 by inducing K+ efflux as a key signaling event, suggesting that K+-permeable ion channels could have high therapeutic potential. In microglia, these include ATP-gated THIK-1 K+ channels and P2X7 receptors, but their interactions and potential therapeutic role in the human brain are unknown. Using a novel specific inhibitor of THIK-1 in combination with patch-clamp electrophysiology in slices of human neocortex, we found that THIK-1 generated the main tonic K+ conductance in microglia that sets the resting membrane potential. Extracellular ATP stimulated K+ efflux in a concentration-dependent manner only via P2X7 and metabotropic potentiation of THIK-1. We further demonstrated that activation of P2X7 was mandatory for ATP-evoked IL-1β release, which was strongly suppressed by blocking THIK-1. Surprisingly, THIK-1 contributed only marginally to the total K+ conductance in the presence of ATP, which was dominated by P2X7. This suggests a previously unknown, K+-independent mechanism of THIK-1 for NLRP3 activation. Nuclear sequencing revealed almost selective expression of THIK-1 in human brain microglia, while P2X7 had a much broader expression. Thus, inhibition of THIK-1 could be an effective and, in contrast to P2X7, microglia-specific therapeutic strategy to contain neuroinflammation.

The Impact of Plasma Membrane Ion Channels on Bone Remodeling in Response to Mechanical Stress, Oxidative Imbalance, and Acidosis

The extracellular milieu is a rich source of different stimuli and stressors. Some of them depend on the chemical–physical features of the matrix, while others may come from the ‘outer’ environment, as in the case of mechanical loading applied on the bones. In addition to these forces, a plethora of chemical signals drives cell physiology and fate, possibly leading to dysfunctions when the homeostasis is disrupted. This variety of stimuli triggers different responses among the tissues: bones represent a particular milieu in which a fragile balance between mechanical and metabolic demands should be tuned and maintained by the concerted activity of cell biomolecules located at the interface between external and internal environments. Plasma membrane ion channels can be viewed as multifunctional protein machines that act as rapid and selective dual-nature hubs, sensors, and transducers. Here we focus on some multisensory ion channels (belonging to Piezo, TRP, ASIC/EnaC, P2XR, Connexin, and Pannexin families) actually or potentially playing a significant role in bone adaptation to three main stressors, mechanical forces, oxidative stress, and acidosis, through their effects on bone cells including mesenchymal stem cells, osteoblasts, osteoclasts, and osteocytes. Ion channel-mediated bone remodeling occurs in physiological processes, aging, and human diseases such as osteoporosis, cancer, and traumatic events.

Upregulation of TLR4-Dependent ATP Production Is Critical for Glaesserella parasuis LPS-Mediated Inflammation

Glaesserella parasuis (G. parasuis), an important pathogenic bacterium, cause Glässer's disease, and has resulted in tremendous economic losses to the global swine industry. G. parasuis infection causes typical acute systemic inflammation. However, the molecular details of how the host modulates the acute inflammatory response induced by G. parasuis are largely unknown. In this study, we found that G. parasuis LZ and LPS both enhanced the mortality of PAM cells, and at the same time, the level of ATP was enhanced. LPS treatment significantly increased the expressions of IL-1β, P2X7R, NLRP3, NF-κB, p-NF-κB, and GSDMD, leading to pyroptosis. Furthermore, these proteins' expression was enhanced following extracellular ATP further stimulation. When reduced the production of P2X7R, NF-κB-NLRP3-GSDMS inflammasome signaling pathway was inhibited, and the mortality of cells was reduced. MCC950 treatment repressed the formation of inflammasome and reduced mortality. Further exploration found that the knockdown of TLR4 significantly reduced ATP content and cell mortality, and inhibited the expression of p-NF-κB and NLRP3. These findings suggested upregulation of TLR4-dependent ATP production is critical for G. parasuis LPS-mediated inflammation, provided new insights into the molecular pathways underlying the inflammatory response induced by G. parasuis, and offered a fresh perspective on therapeutic strategies.

The mechanosensory and mechanotransductive processes mediated by ion channels and the impact on bone metabolism: A systematic review

Mechanical environments were associated with alterations in bone metabolism. Ion channels present on bone cells are indispensable for bone metabolism and can be directly or indirectly activated by mechanical stimulation. This review aimed to discuss the literature reporting the mechanical regulatory effects of ion channels on bone cells and bone tissue. An electronic search was conducted in PubMed, Embase and Web of Science. Studies about mechanically induced alteration of bone cells and bone tissue by ion channels were included. Ion channels including TRP family channels, Ca²⁺ release-activated Ca²⁺ channels (CRACs), Piezo1/2 channels, purinergic receptors, NMDA receptors, voltage-sensitive calcium channels (VSCCs), TREK2 potassium channels, calcium- and voltage-dependent big conductance potassium (BK_Ca) channels, small conductance, calcium-activated potassium (SK_Ca) channels and epithelial sodium channels (ENaCs) present on bone cells and bone tissue participate in the mechanical regulation of bone development in addition to contributing to direct or indirect mechanotransduction such as altered membrane potential and ionic flux. Physiological (beneficial) mechanical stimulation could induce the anabolism of bone cells and bone tissue through ion channels, but abnormal (harmful) mechanical stimulation could also induce the catabolism of bone cells and bone tissue through ion channels. Functional expression of ion channels is vital for the mechanotransduction of bone cells. Mechanical activation (opening) of ion channels triggers ion influx and induces the activation of intracellular modulators that can influence bone metabolism. Therefore, mechanosensitive ion channels provide new insights into therapeutic targets for the treatment of bone-related diseases such as osteopenia and aseptic implant loosening.

Purinergic P2X7 Receptor Mediates the Elimination of Trichinella spiralis by Activating NF-κB/NLRP3/IL-1β Pathway in Macrophages

Trichinellosis is one of most neglected foodborne zoonoses worldwide. During Trichinella spiralis infection, the intestinal immune response is the first line of defense and plays a vital role in the host's resistance. Previous studies indicate that purinergic P2X7 receptor (P2X7R) and pyrin domain-containing protein 3 (NLRP3) inflammasome are involved in the intestinal immune response in T. spiralis infection. However, the precise role of P2X7R and its effect on NLRP3 remains largely underdetermined. In this study, we aimed to investigate the role of P2X7R in the activation of NLRP3 in macrophages during the intestinal immune response against T. spiralis We found that T. spiralis infection upregulated expression of P2X7R and activation of NLRP3 in macrophages in mice. In vivo, P2X7R deficiency resulted in increased intestinal adult and muscle larval burdens, along with decreased expression of NLRP3/interleukin-1β (IL-1β) in macrophages from the infected mice with T. spiralis In In vitro experiments, P2X7R blockade inhibited activation of NLRP3/IL-1β via NF-κB and thus reduced the capacity of macrophages to kill newborn larvae of T. spiralis These results indicate that P2X7R mediates the elimination of T. spiralis by activating the NF-κB/NLRP3/IL-1β pathway in macrophages. Our findings contribute to the understanding of the intestinal immune mechanism of T. spiralis infection.

The P2X7 Receptor in Microglial Cells Modulates the Endolysosomal Axis, Autophagy, and Phagocytosis

Microglial cells regulate neural homeostasis by coordinating both immune responses and clearance of debris, and the P2X₇ receptor for extracellular ATP plays a central role in both functions. The P2X₇ receptor is primarily known in microglial cells for its immune signaling and NLRP3 inflammasome activation. However, the receptor also affects the clearance of extracellular and intracellular debris through modifications of lysosomal function, phagocytosis, and autophagy. In the absence of an agonist, the P2X₇ receptor acts as a scavenger receptor to phagocytose material. Transient receptor stimulation induces autophagy and increases LC3-II levels, likely through calcium-dependent phosphorylation of AMPK, and activates microglia to an M1 or mixed M1/M2 state. We show an increased expression of Nos2 and Tnfa and a decreased expression of Chil3 (YM1) from primary cultures of brain microglia exposed to high levels of ATP. Sustained stimulation can reduce lysosomal function in microglia by increasing lysosomal pH and slowing autophagosome-lysosome fusion. P2X₇ receptor stimulation can also cause lysosomal leakage, and the subsequent rise in cytoplasmic cathepsin B activates the NLRP3 inflammasome leading to caspase-1 cleavage and IL-1β maturation and release. Support for P2X₇ receptor activation of the inflammasome following lysosomal leakage comes from data on primary microglia showing IL-1β release following receptor stimulation is inhibited by cathepsin B blocker CA-074. This pathway bridges endolysosomal and inflammatory roles and may provide a key mechanism for the increased inflammation found in age-dependent neurodegenerations characterized by excessive lysosomal accumulations. Regardless of whether the inflammasome is activated via this lysosomal leakage or the better-known K⁺-efflux pathway, the inflammatory impact of P2X₇ receptor stimulation is balanced between the autophagic reduction of inflammasome components and their increase following P2X₇-mediated priming. In summary, the P2X₇ receptor modulates clearance of extracellular debris by microglial cells and mediates lysosomal damage that can activate the NLRP3 inflammasome. A better understanding of how the P2X₇ receptor alters phagocytosis, lysosomal health, inflammation, and autophagy can lead to therapies that balance the inflammatory and clearance roles of microglial cells.

Cadmium exposure triggers osteoporosis in duck via P2X7/PI3K/AKT-mediated osteoblast and osteoclast differentiation

Cadmium is a common environmental pollutant that accumulates in the bone and kidneys and causes severe health and social problems. However, the effects of Cd on the occurrence of osteoporosis and its mechanism of action in this process are unclear. To test whether Cd-induced osteoporosis is mediated via P2X7/PI3K/AKT signaling, duck bone marrow mesenchymal stem cells (BMSCs) and bone marrow macrophage cells (BMMs) were treated with Cd for 5 days, and duck embryos were treated with Cd_. Micro-CT analysis indicated that Cd-induced osteoporosis occurs in vivo, and histopathology and immunohistochemical analyses also revealed that Cd induced bone damage and the downregulation of osteogenic and bone resorption-related proteins. Cd exposure significantly inhibited the differentiation of BMSCs and BMMs into osteoblasts and osteoclasts in vitro, and promoted osteoblast and osteoclast apoptosis. Cd exposure significantly downregulated the P2X7/PI3K/AKT signaling pathway in vivo and in vitro, and inhibition of this signaling pathway significantly aggravated osteoblast and osteoclast differentiation. Cd exposure also upregulated the OPG/RANKL ratio in vivo and in vitro, further inhibiting osteoclast differentiation. These results demonstrate that Cd causes osteoporosis in duck by inhibiting P2X7/PI3K/AKT signaling and increasing the OPG/RANKL ratio. These results establish a previously unknown mechanism of Cd-induced osteoporosis.

P2X7 Interactions and Signaling - Making Head or Tail of It

Extracellular adenine nucleotides play important roles in cell-cell communication and tissue homeostasis. High concentrations of extracellular ATP released by dying cells are sensed as a danger signal by the P2X7 receptor, a non-specific cation channel. Studies in P2X7 knockout mice and numerous disease models have demonstrated an important role of this receptor in inflammatory processes. P2X7 activation has been shown to induce a variety of cellular responses that are not usually associated with ion channel function, for example changes in the plasma membrane composition and morphology, ectodomain shedding, activation of lipases, kinases, and transcription factors, as well as cytokine release and apoptosis. In contrast to all other P2X family members, the P2X7 receptor contains a long intracellular C-terminus that constitutes 40% of the whole protein and is considered essential for most of these effects. So far, over 50 different proteins have been identified to physically interact with the P2X7 receptor. However, few of these interactions have been confirmed in independent studies and for the majority of these proteins, the interaction domains and the physiological consequences of the interactions are only poorly described. Also, while the structure of the P2X7 extracellular domain has recently been resolved, information about the organization and structure of its C-terminal tail remains elusive. After shortly describing the structure and assembly of the P2X7 receptor, this review gives an update of the identified or proposed interaction domains within the P2X7 C-terminus, describes signaling pathways in which this receptor has been involved, and provides an overlook of the identified interaction partners.

P2X7, a critical regulator and potential target for bone and joint diseases

Abundant evidence indicted that P2X7 receptor show a essential role in human health and some human diseases including hypertension, atherosclerosis, pulmonary inflammation, tuberculosis infection, psychiatric disorders, and cancer. P2X7 receptor also has an important role in some central nervous system diseases such as neurodegenerative disorders. Recently, more research suggested that P2X7 receptor also plays a crucial role in bone and joint diseases. But the effect of P2X7 receptor on skeletal and joint diseases has not been systematically reviewed. In this article, the role of P2X7 receptor in skeletal and joint diseases is elaborated. The activation of P2X7 receptor can ameliorate osteoporosis by inducing a fine balance between osteoclastic resorption and osteoblastic bone formation. The activation of P2X7 receptor can relieve the stress fracture injury by increasing the response to mechanical loading and inducing osteogenesis. But the activation of P2X7 receptor mediates the cell growth and cell proliferation in bone cancer. In addition, the activation of P2X7 receptor can aggravate the process of some joint diseases such as osteoarthritis, rheumatoid arthritis, and acute gouty arthritis. The inhibition of P2X7 receptor can alleviate the pathological process of joint disease to some extent. In conclusion, P2X7 receptor may be a critical regulator and therapeutic target for bone and joint diseases.

The P2X7 receptor: A main player in inflammation

Damage associated molecular patterns (DAMPs) are intracellular molecules released from infected or injured cells to activate inflammatory and reparatory responses. One of the most ancient and conserved DAMPs is extracellular ATP that exerts its phlogistic activity mainly through activation of the P2X7 receptor (P2X7R). The P2X7R is an ATP gated ion channel, expressed by most immune cells, including the monocyte-derived cell lineages, T and B lymphocytes and their precursors. Here we give an overview of recent and established literature on the role of P2X7R in septic and sterile inflammation. P2X7R ability in restraining intracellular bacteria and parasite infection by modulation of the immune response are described, with particular focus on Mycobacteria and Plasmodium. Emerging literature on the role of P2X7 in viral infections such as HIV-1 is also briefly covered. Finally, we describe the numerous intracellular pathways related to inflammation and activated by the P2X7R, including the NLRP3 inflammasome, NF-kB, NFAT, GSK3β and VEGF, and discuss the involvement of P2X7R in chronic diseases. The possible therapeutic applications of P2X7R antagonists are also described.

Blocking of the P2X7 receptor inhibits the activation of the MMP-13 and NF-κB pathways in the cartilage tissue of rats with osteoarthritis

P2X purinoceptor 7 (P2X7) receptor (P2X7R) is known to play a significant role in inflammation and pain-causing diseases, including osteoarthritis (OA). However, the mechanisms of action of P2X7R and its role in OA remain unclear. The articular cartilage is the crucial region in which pathological changes occur in OA, involving the dysregulation of degradation and maintenance mechanisms. In this study, we aimed to reveal the molecular mechanisms of action of P2X7R in articular cartilage in OA-induced pain and inflammation by using AZD9056, an antagonist of P2X7R. We created an animal model of OA by using Wistar rats administered (by intra-articular injection) monosodium iodoacetate (MIA), and the rats with OA were then treated with the P2X7R antagonist, AZD9056. We found that treatment with AZD9056 exerted pain-relieving and anti-inflammatory effects. Importantly, we found that the upregulated expression of interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α), matrix metalloproteinase-13 (MMP-13), substance P (SP) and prostaglandin E2 (PGE2) which was induced by MIA in cartilage tissues was reversed by AZD9056. Western blot analysis was used to examine the expression of inhibitor of nuclear factor-κB (NF-κB) kinase (IKK)α, IKKβ, inhibitor of NF-κB (IκB)α, NF-κB p65 and their phosphorylation forms; they were found to be significantly increased in the knee cartilage tissues from rats with OA; however, opposite effects were observed by the injection of AZD9056. These results implied that P2X7R was associated with the activation of the NF-κB pathway in the development of OA. Our results also revealed that helenalin, an NF-κB pathway inhibitor, decreased the expression of P2X7R, IL-1β, IL-6, TNF-α, SP, PGE2 and MMP-13, which was induced by MIA, in the knee cartilage tissues of rats with OA. On the whole, our findings suggest that P2X7R regulates the MMP-13 and NF-κB pathways in cartilage tissue and mediate OA-induced pain and inflammation.

P2X7 receptors: role in bone cell formation and function

The role of the P2X7 receptor (P2X7R) is being explored with intensive interest in the context of normal bone physiology, bone-related diseases and, to an extent, bone cancer. In this review, we cover the current understanding of P2X7R regulation of bone cell formation, function and survival. We will discuss how the P2X7R drives lineage commitment of undifferentiated bone cell progenitors, the vital role of P2X7R activation in bone mineralisation and its relatively unexplored role in osteocyte function. We also review how P2X7R activation is imperative for osteoclast formation and its role in bone resorption via orchestrating osteoclast apoptosis. Variations in the gene for the P2X7R (P2RX7) have implications for P2X7R-mediated processes and we review the relevance of these genetic variations in bone physiology. Finally, we highlight how targeting P2X7R may have therapeutic potential in bone disease and cancer.

Caveolin-1 regulates P2X7 receptor signaling in osteoblasts

The synthesis of new bone in response to a novel applied mechanical load requires a complex series of cellular signaling events in osteoblasts and osteocytes. The activation of the purinergic receptor P2X(7)R is central to this mechanotransduction signaling cascade. Recently, P2X(7)R have been found to be associated with caveolae, a subset of lipid microdomains found in several cell types. Deletion of caveolin-1 (CAV1), the primary protein constituent of caveolae in osteoblasts, results in increased bone mass, leading us to hypothesize that the P2X(7)R is scaffolded to caveolae in osteoblasts. Thus, upon activation of the P2X(7)R, we postulate that caveolae are endocytosed, thereby modulating the downstream signal. Sucrose gradient fractionation of MC3T3-E1 preosteoblasts showed that CAV1 was translocated to the denser cytosolic fractions upon stimulation with ATP. Both ATP and the more specific P2X(7)R agonist 2'(3')-O-(4-benzoylbenzoyl)ATP (BzATP) induced endocytosis of CAV1, which was inhibited when MC3T3-E1 cells were pretreated with the specific P2X7R antagonist A-839977. The P2X7R cofractionated with CAV1, but, using superresolution structured illumination microscopy, we found only a subpopulation of P2X(7)R in these lipid microdomains on the membrane of MC3T3-E1 cells. Suppression of CAV1 enhanced the intracellular Ca(2+) response to BzATP, suggesting that caveolae regulate P2X(7)R signaling. This proposed mechanism is supported by increased mineralization in CAV1 knockdown MC3T3-E1 cells treated with BzATP. These data suggest that caveolae regulate P2X(7)R signaling upon activation by undergoing endocytosis and potentially carrying with it other signaling proteins, hence controlling the spatiotemporal signaling of P2X(7)R in osteoblasts.

[Genome-wide research on fluid shear stress-sensitive signaling pathways in MC3T3-E1 cells]

OBJECTIVE

To explore the differentially expressed genes and related signaling pathways in MC3T3-E1 osteo- blasts in response to suitable fluid shear stress values and action time with cDNA microarrays.

METHODS

MC3T3-E1 cells cultured on a cover slip were subjected to fluid shear stress using a parallel plate flow chamber. The harvested RNA was used for microarray hybridization comprising approximately 44 170 genes, as well as for the subsequent real-time quantitative polymerase chain reaction validation of expression levels for selected genes. Microarray results were analyzed by using both GO and Pathway analysis.

RESULTS

Microarray analysis indicated that 884 differentially expressed genes were found. Among these genes, 444 were upregulated, whereas 440 were downregulated. The Notch signal and RIG- I -like receptor signaling pathways were involved in the Pathway analysis. GO analysis mainly involved different functional classifications, such as prostaglandin biosynthesis, nitric oxide-mediated signal transduction, calcium mediated signal, and cellular immune response, among others.

CONCLUSION

The mechanism underlying the protective effect of fluid shear stress on MC3T3-E1 cells might be related to promoting cell survival- and inhibiting cell apoptosis-related signaling pathways and biological processes.

Hydraulic Pressure during Fluid Flow Regulates Purinergic Signaling and Cytoskeleton Organization of Osteoblasts

During physiological activities, osteoblasts experience a variety of mechanical forces that stimulate anabolic responses at the cellular level necessary for the formation of new bone. Previous studies have primarily investigated the osteoblastic response to individual forms of mechanical stimuli. However in this study, we evaluated the response of osteoblasts to two simultaneous, but independently controlled stimuli; fluid flow-induced shear stress (FSS) and static or cyclic hydrostatic pressure (SHP or CHP, respectively). MC3T3-E1 osteoblasts-like cells were subjected to 12dyn/cm² FSS along with SHP or CHP of varying magnitudes to determine if pressure enhances the anabolic response of osteoblasts during FSS. For both SHP and CHP, the magnitude of hydraulic pressure that induced the greatest release of ATP during FSS was 15 mmHg. Increasing the hydraulic pressure to 50 mmHg or 100 mmHg during FSS attenuated the ATP release compared to 15 mmHg during FSS. Decreasing the magnitude of pressure during FSS to atmospheric pressure reduced ATP release to that of basal ATP release from static cells and inhibited actin reorganization into stress fibers that normally occurred during FSS with 15 mmHg of pressure. In contrast, translocation of nuclear factor kappa B (NFκB) to the nucleus was independent of the magnitude of hydraulic pressure and was found to be mediated through the activation of phospholipase-C (PLC), but not src kinase. In conclusion, hydraulic pressure during FSS was found to regulate purinergic signaling and actin cytoskeleton reorganization in the osteoblasts in a biphasic manner, while FSS alone appeared to stimulate NFκB translocation. Understanding the effects of hydraulic pressure on the anabolic responses of osteoblasts during FSS may provide much needed insights into the physiologic effects of coupled mechanical stimuli on osteogenesis.

The P2X7 receptor: a key player in immune-mediated bone loss?

Inflammatory diseases are often multiorganic diseases with manifestations not related directly to the primary affected organ. They are often complicated by a generalized bone loss that subsequently leads to osteoporosis and bone fractures. The exact mechanism for the accompanying bone loss is not understood in full detail, but factors such as glucocorticoid treatment, immobilization, malnutrition, and insufficient intake of vitamin D play a role. However, it has become evident that the inflammatory process itself is involved and the resulting bone loss is termed immune-mediated bone loss. It stems from an increase in bone resorption and the pro-inflammatory cytokines tumor necrosis factor alpha and interleukin 1 beta and has been shown to not only mediate the inflammatory response but also to strongly stimulate bone degradation. The purinergic P2X7 receptor is central in the processing of these two cytokines and in the initiation of the inflammatory response, and it is a key molecule in the regulation of both bone formation and bone resorption. The aim of this review is therefore to provide evidence-based novel hypotheses of the role of ATP-mediated purinergic signalling via the P2X7 receptor in immune-mediated bone loss and -osteoporosis.

Purinergic signalling in the musculoskeletal system

It is now widely recognised that extracellular nucleotides, signalling via purinergic receptors, participate in numerous biological processes in most tissues. It has become evident that extracellular nucleotides have significant regulatory effects in the musculoskeletal system. In early development, ATP released from motor nerves along with acetylcholine acts as a cotransmitter in neuromuscular transmission; in mature animals, ATP functions as a neuromodulator. Purinergic receptors expressed by skeletal muscle and satellite cells play important pathophysiological roles in their development or repair. In many cell types, expression of purinergic receptors is often dependent on differentiation. For example, sequential expression of P2X5, P2Y1 and P2X2 receptors occurs during muscle regeneration in the mdx model of muscular dystrophy. In bone and cartilage cells, the functional effects of purinergic signalling appear to be largely negative. ATP stimulates the formation and activation of osteoclasts, the bone-destroying cells. Another role appears to be as a potent local inhibitor of mineralisation. In osteoblasts, the bone-forming cells, ATP acts via P2 receptors to limit bone mineralisation by inhibiting alkaline phosphatase expression and activity. Extracellular ATP additionally exerts significant effects on mineralisation via its hydrolysis product, pyrophosphate. Evidence now suggests that purinergic signalling is potentially important in several bone and joint disorders including osteoporosis, rheumatoid arthritis and cancers. Strategies for future musculoskeletal therapies might involve modulation of purinergic receptor function or of the ecto-nucleotidases responsible for ATP breakdown or ATP transport inhibitors.

Suramin: a potential therapy for diabetic nephropathy

Objective

To determine whether delayed administration of a single dose of suramin, a drug that has been used extensively in humans to treat trypanosomiasis, attenuates renal injury in a leptin receptor deficient C57BLKS/J db/db type 2 diabetic nephropathy (T2DN) mouse model.

Research Design and Methods

Groups of female non-diabetic (control) db/m and diabetic db/db mice of 8 and 16 weeks of age, respectively, were treated with suramin (10 mg/kg) or saline i.v. All animals were euthanized one week later. Measurements in mice 1 week following treatment included the following: body weight; blood glucose; urinary protein excretion; pathological lesions in glomeruli and proximal tubules; changes in protein expression of pro-inflammatory transcription factor nuclear factor κB (NF-κB) and intracellular adhesion molecule-1 (ICAM-1), profibrotic transforming growth factor-β1 (TGF-β1), phospho-SMAD-3 and alpha-smooth muscle actin (α-SMA); and immunohistochemical analysis of leukocyte infiltration and collagen 1A2 (COL1A2) deposition.

Results

Immunoblot analysis revealed increased NF-κB, ICAM-1, TGF-β1, phospho-SMAD-3, and α-SMA proteins in both 9 and 17 week db/db mice as compared to db/m control mice. Immunohistochemical analysis revealed moderate leukocyte infiltration and collagen 1A2 (COL1A2) deposition in 9 week db/db mice that was increased in the 17 week db/db mice. Importantly, suramin significantly decreased expression of all these markers in 9 week db/db mice and partially decreased in 17 week db/db mice without altering body weight, blood glucose or urinary protein excretion. There was no difference in creatinine clearance between 9 week db/m and db/db mice ± suramin. Importantly, in the 17 week db/db mice suramin intervention reversed the impaired creatinine clearance and overt histological damage.

Conclusions

Delayed administration of a single dose of suramin in a model of T2DN attenuated inflammation and fibrosis as well as improved renal function, supporting the use of suramin in T2DN.

The effect of P2X7 receptor activation on nuclear factor-κB phosphorylation induced by status epilepticus in the rat hippocampus

Nuclear factor-kappa B (NFκB) signal is essential for neuronal survival and its activation may protect neuron against various stimuli. Since purinergic signals activate NFκB through the P2X7 receptor, we investigated the distinct pattern of NF-κB phosphorylation in neurons by P2X7 receptor activation following status epilepticus (SE) in an effort to understand the role of P2X7 receptor in epileptogenic insult. In non-SE animals, 2'(3')-O-(4-benzoyl)benzoyl adenosine 5'-triphosphate (BzATP, a P2X7R agonist) treatment increased only p52-Ser869 NF-κB phosphorylation in neuron. Following SE, p52-Ser865, p52-Ser869, p65-Ser276, p65-Ser311, p65-Ser468, and p65-Ser529 NF-κB phosphorylation was significantly decreased in CA1 and CA3 neurons. However, BzATP treatment prevented reductions in p65-Ser276, p65-Ser311, p65-Ser529, and p52-Ser869 NF-κB phosphorylations in CA1 and/or CA3 neurons induced by SE. Furthermore, BzATP treatment reduced SE-induced p65-Ser311, p65-Ser468, p65-Ser536, and p52-Ser869 NF-κB phosphorylations in astrocytes. These findings indicate that P2X7 functions may be involved in the regulation of SE-induced reactive astrocytes and neuronal degeneration via NF-κB phosphorylations in response to pilocarpine-induced SE in the rat hippocampus.