The ß2 subunit E155 residue as a proton sensor at the binding site on GABA type A receptors.

GABA type A receptor plays a key role in inhibitory signaling in the adult central nervous system. This receptor can be modulated by protons but the underlying molecular mechanisms have not been fully explored. To find possible pH-sensor residues, a comparative study for proton-activated GLIC channel and α1ß2γ2 GABA receptor was performed and pK 's of respective residues were estimated by numerical algorithms which consider local interactions. ß E155, located at the GABA binding site, showed pKa values close to physiological values and dependence on the receptor state and ligation, suggesting a role in modulation by pH. To validate this prediction, pH sensitivity of current responses to GABA was investigated using patch-clamp technique for WT and mutated (ß2E155[C, S, Q, L]) GABA receptors. Cysteine mutation preserved pH sensitivity. However, for remaining mutants, the sensitivity to acidification (pH = 6.0) was reduced becoming not statistically significant. The effect of alkaline pH (8.0) was maintained for all mutants with exception for ß2E155L for which it was nearly abolished. To further explore the impact of considered mutations, molecular docking was performed which indicated that pH modulation is probably affected by interplay between binding site residues, zwitterion GABA and protons. These data, altogether, indicate that mutation of ß2E155 to hydrophobic residue (L) maximally impaired pH modulation while for polar substitutions the effect was smaller. In conclusion, our data provide evidence that a key binding site residue ß2E155 plays an important role in proton sensitivity of GABA receptor.

Mutations at the M2 and M3 Transmembrane Helices of the GABAARs α1 and ß2 Subunits Affect Primarily Late Gating Transitions Including Opening/Closing and Desensitization.

GABA type A receptors (GABAARs) belong to the pentameric ligand-gated ion channel (pLGIC) family and play a crucial role in mediating inhibition in the adult mammalian brain. Recently, a major progress in determining the static structure of GABAARs was achieved, although precise molecular scenarios underlying conformational transitions remain unclear. The ligand binding sites (LBSs) are located at the extracellular domain (ECD), very distant from the receptor gate at the channel pore. GABAAR gating is complex, comprising three major categories of transitions: openings/closings, preactivation, and desensitization. Interestingly, mutations at, e.g., the ligand binding site affect not only binding but often also more than one gating category, suggesting that structural determinants for distinct conformational transitions are shared. Gielen and co-workers (2015) proposed that the GABAAR desensitization gate is located at the second and third transmembrane segment. However, studies of our and others' groups indicated that other parts of the GABAAR macromolecule might be involved in this process. In the present study, we asked how selected point mutations (ß2G254V, α1G258V, α1L300V, and ß2L296V) at the M2 and M3 transmembrane segments affect gating transitions of the α1ß2γ2 GABAAR. Using high resolution macroscopic and single-channel recordings and analysis, we report that these substitutions, besides affecting desensitization, also profoundly altered openings/closings, having some minor effect on preactivation and agonist binding. Thus, the M2 and M3 segments primarily control late gating transitions of the receptor (desensitization, opening/closing), providing a further support for the concept of diffuse gating mechanisms for conformational transitions of GABAAR.

Characteristics of MIC-1 antlerogenic stem cells and their effect on hair growth in rabbits.

AIM: We characterized growth factors produced by MIC-1 antlerogenic stem cells and attempted to apply those cells to stimulate hair growth in rabbits. MATERIALS AND METHODS: We evaluated the gene and protein expression of growth factors by immunocytochemical and molecular biology techniques in MIC-1 cells. An animal model was used to assess the effects of xenogenous stem cells on hair growth. In the experimental group, rabbits were intradermally injected with MIC-1 stem cells, whereas the control group rabbits were given vehicle-only. After 1, 2 and 4 weeks, skin specimen were collected for histological and immunohistochemical tests. RESULTS: MIC-1 antlerogenic stem cells express growth factors, as confirmed at the mRNA and protein levels. Histological and immunohistochemical analysis demonstrated an increase in the number of hair follicles, as well as the amount of secondary hair in the follicles, without an immune response in animals injected intradermally with MIC-1 cells, compared to animals receiving vehicle-alone. CONCLUSION: MIC-1 cells accelerated hair growth in rabbits due to the activation of cells responsible for the regulation of the hair growth cycle through growth factors. Additionally, the xenogenous cell implant did not induce immune response.

In vitro and in vivo matrix metalloproteinase expression after photodynamic therapy with a liposomal formulation of aminolevulinic acid and its methyl ester.

Photodynamic therapy (PDT) is a well-known method for the treatment of malignant tumors, and its principles have been well established over the past 30 years. This therapy involves the application of a chemical called a photosensitizer and its subsequent excitation with light at the appropriate wavelength and energy. Topical photodynamic therapy with aminolevulinic acid (5-ALA) is an alternative therapy for many malignant processes, including nonmelanoma skin cancers such as basal-cell carcinoma (BCC). Our novel approach for this study was to use a liposomal formulation of 5-ALA and its methyl ester (commercially available as metvix) both in vitro and in vivo, and to check whether the liposome-entrapped precursors of photosensitizers can induce the expression of metalloproteinases (MMPs) in animal tumor cells and in other tissues from tumor-bearing rats and in selected cell lines in vitro. We also checked whether the application of tissue inhibitors of matrix metalloproteinases (TIMPs) has any effect on MMPs in the above-mentioned experimental models, and if they can cause complete inhibition of MMP expression. Immunohistochemical studies revealed that after the PDT, the intensity of expression of MMPs in healthy animals was very low and seen in single cells only. After the PDT in tumor-bearing rats, MMP-3 was expressed in the tumor cells with the highest intensity of staining in the tissues directly adjacent to the tumors, while MMP-2 and -9 were not found. In the control groups, there was no observed expression of MMPs. In vitro studies showed that MMP-3 was expressed in MCF-7 cells after PDT, but MMP-9 was not observed and MMP-2 was only seen in single cases. Our studies confirmed that the application of an MMP-3 inhibitor may block an induction of MMP-3 expression which had previously been initiated by PDT. The preliminary data obtained from cancer patients revealed that new precursors are effective in terms of PDT, and that using MMP inhibitors should be considered as a potential enhancing factor in clinical PDT.

alpha-Amanitin induced apoptosis in primary cultured dog hepatocytes.

Amatoxin poisoning is caused by mushroom species belonging to the genera Amanita, Galerina and Lepiota with the majority of lethal mushroom exposures attributable to Amanita phalloides. High mortality rate in intoxications with these mushrooms is principally a result of the acute liver failure following significant hepatocyte damage due to hepatocellular uptake of amatoxins. A wide variety of amatoxins have been isolated; however, alpha-amanitin (alpha-AMA) appears to be the primary toxin. Studies in vitro and in vivo suggest that alpha-AMA does not only cause hepatocyte necrosis, but also may lead to apoptotic cell death. The objective of this study was to evaluate the complex hepatocyte apoptosis in alpha-AMA cytotoxicity. All experiments were performed on primary cultured canine hepatocytes. The cells were incubated for 12 h with alpha-AMA at a final concentration of 1, 5, 10 and 20 microM. Viability test (MTT assay), apoptosis evaluation (TUNEL reaction, detection of DNA laddering and electron microscopy) were performed at 6 and 12 h of exposure to alpha-AMA. There was a clear correlation between hepatocyte viability, concentration of alpha-AMA and time of exposure to this toxin. The decline in cultured dog hepatocyte viability during the exposure to alpha-AMA is most likely preceded by enhanced cellular apoptosis. Our results demonstrate that apoptosis might contribute to pathogenesis of the severe liver injury in the course of amanitin intoxication, particularly during the early phase of poisoning.

Experimental xenoimplantation of antlerogenic cells into mandibular bone lesions in rabbits: two-year follow-up.

Different types of cells require activation, and take part in annual, dynamic growth of deer antlers. Stem cells play the most important role in this process. This report shows the results of a two-year long observation of xenogenic implant of antlerogenic stem cells (cell line MIC-1). The cells were derived from growing antler of a deer (Cervus elaphus), seeded onto Spongostan and placed in postoperative lesions of mandibular bones of 15 experimental rabbits. The healing process observed in the implantation sites in all rabbits was normal, and no local inflammatory response was ever observed. Histological and immunohistochemical evaluations were performed after 1, 2, 6, 12 and 24 months, and confirmed the participation of xenogenic cells in the regeneration processes, as well as a lack of rejection of the implants. The deficiencies in the bones were replaced by newly formed, thick fibrous bone tissue that underwent mineralization and was later remodelled into lamellar bone. The results of the experiment with rabbits allow us to believe that antlerogenic cells could be used in reconstruction of bone tissues in other species as well.

Effect of melatonin on melanoma cells subjected to UVA and UVB radiation in In vitro studies.

Studies performed in vivo and in vitro have shown that exogenous melatonin (Mel) exerts oncostatic effects on melanoma cells. Although the protective effect of Mel on skin and cells exposed mainly to UVB has been documented, effects of Mel have not yet been examined on melanoma cells exposed to UVA. Our investigations aimed at examination of the effect of Mel alone (0, 10(-3), 10(-6) and 10(-9) M), and after its addition to the culture medium for 30 minutes before exposure of melanoma cells to UVA (15 J/cm(2)) or UVB (30 mJ/cm(2), 60 mJ/cm(2)). Viability of the cells was examined using the colorimetric sulphorhodamine B test. Mel added to the medium at concentrations of 10(-3)-10(-8) M was found to increase the number of melanoma cells as compared to the control (cells with no Mel) after 24 hours. Compared to exposed cells without Mel, at 10(-3) M Mel, melanoma cells exposed to 30 mJ/cm(2) UVB increased in number and at 10(-9) M increased the survival of those exposed to 60 mJ/cm(2) UVB. The cells exposed to UVA (15 J/cm(2)) were protected by Mel at 10(-6) and 10(-9) M. Physiological concentrations of Mel exerted no oncostatic effects on the BM cell line used here. In addition, the pharmacological Mel concentrations stimulated proliferation of the cells. Beyond doubt, we have confirmed that Mel represents a substance which protects cells from UVA and UVB action in in vitro experiments.

Effect of melatonin on human keratinocytes and fibroblasts subjected to UVA and UVB radiation In vitro.

Skin represents one of the extrapineal sites of melatonin (Mel) synthesis. In the skin Mel plays, for example, the role of an antioxidant which scavenges and inactivates free radicals arising due to UV irradiation. Although the protective effect of Mel on skin and cells irradiated mainly with UVB has been documented, to date no comparison has been made for the effects of Mel on cells exposed to UVA. Our study aimed at evaluating the effect of Mel (0, 10(-3), 10(-6) or 10(-9) M) added to culture medium 30 minutes before exposure of keratinocytes and fibroblasts to irradiation with UVA (15 J/cm(2)) and UVB (30 mJ/cm(2), 60 mJ/cm(2)). Viability of the cells was evaluated using sulphorhodamine (SRB) colorimetric test. Mel at 10(-3) M increased the number of surviving keratinocytes and at 10(-6) M increased the number of surviving fibroblasts exposed to UVB (30 mJ/cm(2), 60 mJ/cm(2)) as compared to cells exposed only to radiation. In addition, 10(-6) M protected keratinocytes exposed to the dose of 30 mJ/cm(2). Mel at 10(-3) M exerted a protective effect on both types of cells irradiated with UVA (15 J/cm(2)). As documented by our studies, Mel protects skin cells from the action of UVA and UVB. The protective effect of different Mel concentrations might result from variable expression of melatonin receptors.

Failure of benzylpenicillin, N-acetylcysteine and silibinin to reduce alpha-amanitin hepatotoxicity.

BACKGROUND: Intoxications caused by amanitin-containing mushrooms represent an unresolved problem in clinical toxicology. The objective of this study was a comparative evaluation of benzylpenicillin (Bp), acetylcysteine (ACC) and silibinin (Sil) efficacy as antidotes in hepatocytes intoxicated with alpha-amanitin (alpha-AMA). MATERIALS AND METHODS: All experiments were performed on cultured canine hepatocytes. Cytotoxicity evaluation of cultured cells (MTT assay, extracellular lactate dehydrogenase activity) was performed at 12, 24 and 48 h of exposure to alpha-AMA and/or antidotes. RESULTS: Following 24 and 48 h exposure there was a significant decline of hepatocyte viability and an increase of lactate dehydrogenase activity in groups exposed to alpha-AMA and in groups exposed simultaneously to alpha-AMA and antidotes. Moreover, hepatocyte viability and lactate dehydrogenase activity in all these groups were similar. Administration of studied antidotes without alpha-AMA, was not associated with any adverse effects in hepatocytes. CONCLUSION: All antidotes tested in this study against alpha-AMA were not effective in canine hepatocyte cultures.

Early morphological and functional alterations in canine hepatocytes due to alpha-amanitin, a major toxin of Amanita phalloides.

The toadstool death cap (Amanita phalloides) and its subspecies, destroying angel (A. virosa) and death angel (A. verna) are responsible for nearly 95% of all fatal mushroom poisonings. High mortality rate in A. phalloides intoxications is principally a result of the acute liver failure following significant hepatocyte damage due to hepatocellular uptake of amanitins, the major toxins of this mushroom. This study evaluated early morphological and functional alterations in hepatocytes exposed to different concentrations of alpha-amanitin (alpha-AMA). All experiments were performed on cultured canine hepatocytes since intoxicated with A. phalloides dogs have clinical course and pathological findings similar to those seen in humans. The overall functional integrity and viability of cultured hepatocytes were assessed using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and by measurements of lactate dehydrogenase (LDH), total protein, and urea levels. Our results showed that the course of alpha-AMA toxicity in cultured dog hepatocytes is divided into two phases. The first phase comprises functional cell impairments expressed by significant increase of LDH activity and inhibition of protein and urea synthesis when compared with the control group. This is followed by discrete changes in hepatocyte ultrastructure, including marginalization and condensation of nuclear chromatin, as well as formation of the foamlike cytoplasm. The second stage is lethal and is characterized by ongoing necrosis, and/or apoptosis. This may be related to dose of toxin and time of exposure.

Development of foreign body giant cells in response to implantation of Spongostan as a scaffold for cartilage tissue engineering.

Spongostan, a gelatinous haemostatic sponge, is used in surgery. Moreover, Spongostan may serve as a scaffold for proteins or cells implanted into defects. At the site of biomaterial implantation, foreign body giant cells (FBGCs) may develop which are responsible for Spongostan degradation. The purpose of the present study was to examine whether Spongostan may serve as a scaffold in allogenic grafting of chondrocytes developed from rabbit auricular cartilage. The obtained results indicate that Spongostan fulfils its function as a cell scaffold, induces no inflammatory reaction and involves development of foreign body giant cells which participate in the process of its degradation. Microscopic observation showed that FBGCs manifest presence of cytoplasmic projections and lysosomes, which participate in phagocytosis of the applied scaffold.

[The structure of NF- kappaB family proteins and their role in apoptosis]. / Budowa bialek z rodziny NF-kappaB i ich rola w procesieapoptozy.

The NF-kappaB protein family encompasses transcription factors involved in controlling the expressions of genes which are crucial for several processes taking part at the cellular level. Five transcription factors, differing in the structure of the polypeptide chain of the C terminus, have been discovered in mammals so far. NF-kappaB heterodimers play a physiological role and their activity remains under strict control. The most common is a dimer composed of p50/RelA (p50/p65) proteins. NF-kappaB complexes are retained in the cytoplasm due to their interaction with kappaB inhibitors (IkappaB). When stimulated, IkappaB undergoes phosphorylation and then degradation in a proteasome, while the free NF-kappaB dimer is translocated to the cell nucleus, where it regulates the transcription of target genes. A key role in IkappaB phosphorylation is played by kinases of kappaB inhibitors (IKKs). They involve a protein complex encompassing two enzymatic subunits, IKKalpha and IKKbeta, and the regulatory subunit NEMO. Three principal pathways of NF-kappaB activation are distinguished, which involve distinct NF-kappaB dimers. Activators of the classical triggering pathway include, among others, lipopolysaccharide composing the envelope of Gram-negative bacteria, viruses, and pro-inflammatory cytokines. Another activation pathway is induced by the action of such proteins as lymphotoxin beta. NF-kappaB transcription factor also becomes activated in response to DNA damage. As generally recognized, NF-kappaB exerts an anti-apoptotic action, promoting the survival of defective cells, which may result in the development of several tumors. Nevertheless, recent reports also point to a pro-apoptotic activity of NF-kappaB. This review is an attempt to present current knowledge on the involvement of NF-kappaB transcription factor in cell death by apoptosis.

[The protective role of melatonin in the course of UV exposure]. / Ochronna rola melatoniny podczas dzialaniapromieniowania UV.

Melatonin (Mel) is a hormone synthesized mainly by the pineal gland. The principal function of Mel in the body involves the control of circadian and seasonal rhythms. Moreover, numerous reports document its anti-oxidative properties. Skin and eyes are particularly sensitive to the noxious influences exerted by UV exposure. The most dangerous radiation of the UVB (ultraviolet-B) and UVA (ultraviolet-A) range induces the formation of reactive oxygen species and thus stimulates the apoptosis of exposed cells. In numerous in vivo and in vitro studies, Mel produced in the skin and eye has been found to protect against the sequelae of UVB- and UVA-induced oxidative stress. In in vitro studies involving UVB irradiation of keratinocytes, fibroblasts, and leukocytes, Mel applied in both pharmacological (10(-3) and 10(-4 )M) and physiological doses (10(-7) and 10(-9) M) decreased the fraction of damaged cells. A similar pattern of Mel action at various doses of Mel probably reflected the presence of melatonin receptors (mainly MT1 receptors) in skin and eye cells. Moreover, intraperitoneally administered Mel or Mel applied to the skin before UVB exposure protects against the development of cataract and erythema, respectively. Thus only intracellular Mel may protect cells against the effects of UVB exposure. Although there are numerous reports describing the effects of UVA on cells of the skin and eye, no studies have described the anti-oxidative properties of Mel in relation to UVA-irradiated cells.