Apolipoprotein A-I Supports MSCs Survival under Stress Conditions.

Clinical trials have shown the safety of mesenchymal stem/stromal cells (MSCs) transplantation, but the effectiveness of these treatments is limited. Since, transplanted MSCs will undergo metabolic disturbances in the bloodstream, we investigated the influence of blood plasmas of type 2 diabetes (T2D) patients on MSCs viability and examined whether apolipoprotein A-I (apoA-I) could protect cells from stressful conditions of serum deprivation (SD), hypoxia, and elevated concentrations of reactive oxygen species (ROS). ApoA-I exhibits anti-inflammatory, immune activities, improves glycemic control, and is suitable for T2D patients but its influence on MSCs remains unknown. For the first time we have shown that apoA-I decreases intracellular ROS and supports proliferative rate of MSCs, thereby increasing cell count in oxidation conditions. ApoA-I did not influence cell cycle when MSCs were predominantly in the G0/G1 phases under conditions of SD/hypoxia, activated proliferation rapidly, and reduced apoptosis during MSCs transition to the oxygenation or oxidation conditions. Finally, it was found that the blood plasma of T2D individuals had a cytotoxic effect on MSСs in 39% of cases and had a wide variability of antioxidant properties. ApoA-I protects cells under all adverse conditions and can increase the efficiency of MSCs transplantation in T2D patients.

Lateralized response of dynorphin a peptide levels after traumatic brain injury.

Traumatic brain injury (TBI) induces a cascade of primary and secondary events resulting in impairment of neuronal networks that eventually determines clinical outcome. The dynorphins, endogenous opioid peptides, have been implicated in secondary injury and neurodegeneration in rodent and human brain. To gain insight into the role of dynorphins in the brain's response to trauma, we analyzed short-term (1-day) and long-term (7-day) changes in dynorphin A (Dyn A) levels in the frontal cortex, hippocampus, and striatum, induced by unilateral left-side or right-side cortical TBI in mice. The effects of TBI were significantly different from those of sham surgery (Sham), while the sham surgery also produced noticeable effects. Both sham and TBI induced short-term changes and long-term changes in all three regions. Two types of responses were generally observed. In the hippocampus, Dyn A levels were predominantly altered ipsilateral to the injury. In the striatum and frontal cortex, injury to the right (R) hemisphere affected Dyn A levels to a greater extent than that seen in the left (L) hemisphere. The R-TBI but not L-TBI produced Dyn A changes in the striatum and frontal cortex at 7 days after injury. Effects of the R-side injury were similar in the two hemispheres. In naive animals, Dyn A was symmetrically distributed between the two hemispheres. Thus, trauma may reveal a lateralization in the mechanism mediating the response of Dyn A-expressing neuronal networks in the brain. These networks may differentially mediate effects of left and right brain injury on lateralized brain functions.

Control of chronic pain by the ubiquitin proteasome system in the spinal cord.

Chronic pain is maintained in part by long-lasting neuroplastic changes in synapses and several proteins critical for synaptic plasticity are degraded by the ubiquitin-proteasome system (UPS). Here, we show that proteasome inhibitors administered intrathecally or subcutaneously prevented the development and reversed nerve injury-induced pain behavior. They also blocked pathological pain induced by sustained administration of morphine or spinal injection of dynorphin A, an endogenous mediator of chronic pain. Proteasome inhibitors blocked mechanical allodynia and thermal hyperalgesia in all three pain models although they did not modify responses to mechanical stimuli, but partially inhibited responses to thermal stimuli in control rats. In the spinal cord, these compounds abolished the enhanced capsaicin-evoked calcitonin gene-related peptide (CGRP) release and dynorphin A upregulation, both elicited by nerve injury. Model experiments demonstrated that the inhibitors may act directly on dynorphin-producing cells, blocking dynorphin secretion. Thus, the effects of proteasome inhibitors on chronic pain were apparently mediated through several cellular mechanisms indispensable for chronic pain, including those of dynorphin A release and postsynaptic actions, and of CGRP secretion. Levels of several UPS proteins were reduced in animals with neuropathic pain, suggesting that UPS downregulation, like effects of proteasome inhibitors, counteracts the development of chronic pain. The inhibitors did not produce marked or disabling motor disturbances at doses that were used to modify chronic pain. These results suggest that the UPS is a critical intracellular regulator of pathological pain, and that UPS-mediated protein degradation is required for maintenance of chronic pain and nociceptive, but not non-nociceptive responses in normal animals.

Malaria circumsporozoite protein inhibits the respiratory burst in Kupffer cells.

After transmission by infected mosquitoes, malaria sporozoites rapidly travel to the liver. To infect hepatocytes, sporozoites traverse Kupffer cells, but surprisingly, the parasites are not killed by these resident macrophages of the liver. Here we show that Plasmodium sporozoites and recombinant circumsporozoite protein (CSP) suppress the respiratory burst in Kupffer cells. Sporozoites and CSP increased the intracellular concentration of cyclic adenosyl mono-phosphate (cAMP) and inositol 1,4,5-triphosphate in Kupffer cells, but not in hepatocytes or liver endothelia. Preincubation with cAMP analogues or inhibition of phosphodiesterase also inhibited the respiratory burst. By contrast, adenylyl cyclase inhibition abrogated the suppressive effect of sporozoites. Selective protein kinase A (PKA) inhibitors failed to reverse the CSP-mediated blockage and stimulation of the exchange protein directly activated by cAMP (EPAC), but not PKA inhibited the respiratory burst. Both blockage of the low-density lipoprotein receptor-related protein (LRP-1) with receptor-associated protein and elimination of cell surface proteoglycans inhibited the cAMP increase in Kupffer cells. We propose that by binding of CSP to LRP-1 and cell surface proteoglycans, malaria sporozoites induce a cAMP/EPAC-dependent, but PKA-independent signal transduction pathway that suppresses defence mechanisms in Kupffer cells. This allows the sporozoites to safely pass through these professional phagocytes and to develop inside neighbouring hepatocytes.

Translocation of dynorphin neuropeptides across the plasma membrane. A putative mechanism of signal transmission.

Several peptides, including penetratin and Tat, are known to translocate across the plasma membrane. Dynorphin opioid peptides are similar to cell-penetrating peptides in a high content of basic and hydrophobic amino acid residues. We demonstrate that dynorphin A and big dynorphin, consisting of dynorphins A and B, can penetrate into neurons and non-neuronal cells using confocal fluorescence microscopy/immunolabeling. The peptide distribution was characterized by cytoplasmic labeling with minimal signal in the cell nucleus and on the plasma membrane. Translocated peptides were associated with the endoplasmic reticulum but not with the Golgi apparatus or clathrin-coated endocytotic vesicles. Rapid entry of dynorphin A into the cytoplasm of live cells was revealed by fluorescence correlation spectroscopy. The translocation potential of dynorphin A was comparable with that of transportan-10, a prototypical cell-penetrating peptide. A central big dynorphin fragment, which retains all basic amino acids, and dynorphin B did not enter the cells. The latter two peptides interacted with negatively charged phospholipid vesicles similarly to big dynorphin and dynorphin A, suggesting that interactions of these peptides with phospholipids in the plasma membrane are not impaired. Translocation was not mediated via opioid receptors. The potential of dynorphins to penetrate into cells correlates with their ability to induce non-opioid effects in animals. Translocation across the plasma membrane may represent a previously unknown mechanism by which dynorphins can signal information to the cell interior.