Muayad Zahalka - Academia.edu (original) (raw)

Papers by Muayad Zahalka

Allicin, the main organic allyl sulfur component in garlic, exhibits immune-stimulatory and antit... more Allicin, the main organic allyl sulfur component in garlic, exhibits immune-stimulatory and antitumor properties. Allicin stimulated [3H]thymidine incorporation in mouse splenocytes and enhanced cell-mediated cytotoxicity in human peripheral mononuclear cells. Multiple administration (i.p.) of allicin elicited a marked antitumor effect in mice inoculated with B-16 melanoma and MCA-105 ®brosarcoma. The immune-stimulatory and antitumor effects of allicin are characterized by a bell-shaped curve, i.e. allicin at high, supra-optimal concentrations is less effective or inhibitory. Allicin induced activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in human peripheral mononuclear cells, and also in wild-type Jurkat T-cells. Allicin failed to activate ERK1/2 in Jurkat T cells that express p21ras, in which Cys118 was replaced by Ser. These cells are not susceptible to redox-stress modi®cation and activation. We postulate that the immune stimulatory effect of allicin is med...

Current Topics in Microbiology and Immunology, 1998

The malignant process is, in many aspects, a distorted image of normal physiological activities. ... more The malignant process is, in many aspects, a distorted image of normal physiological activities. In this respect, the dissemination mechanism of malignant lymphomas may display a hazy reflection of normal cell migration, an essential function of the lymphoid system. The successful response of the individual’s defense machinery against invading microorganisms is largely due to its ability to rapidly mobilize leukocytes to the site of infection. Cell motility in blood, lymph, lymphoid organs and tissues is highly dependent on the coordinated activity of different cell adhesion molecules. These are implicated in the transendothelial migration of intravasated and extravasated cells, the capture of cells by the luminal surface of the endothelium, cell rolling and cell arrest in the vasculature, binding of lymphocytes to the high endothelial venule (HEV) of the lymph node, as well as subsequent cell lodgment in organ parenchyma (a process known as cell homing), and cell migration on extracellular matrix (ECM) (Parkhurst and Saltzman 1992; Picker and Butcher 1992; Thomas et al. 1992; Springer 1994; Ley and Tedder 1995). Three pairs of adhesion receptor and counterreceptor families are implicated in the interaction between leukocytes and their target cells in the endothelium and tissues: (1) integrins, which target molecules of the immunoglobulin superfamily (IgSF) or ECM components, (2) selectins, which interact with sialylated carbohydrate determinants O-linked to mucin-like molecules (also known as addressins), and (3) CD44 receptors with binding affinity for matrix and cell surface constituents (Ruoslahti 1991; Yamada 1991; Picker and Butcher 1992; Lesley et al. 1993; Springer 1994; Naor et al. 1997).

Journal of immunology (Baltimore, Md. : 1950), Jan 15, 1993

The same integrin adhesion molecules used by normal leukocytes for traffic and localization in in... more The same integrin adhesion molecules used by normal leukocytes for traffic and localization in inflammation sites may be used by malignant cells for dissemination. Identifying the adhesion molecules and then blocking them with appropriate antibody may therefore prove useful for controlling tumor spread. This prediction was tested on a spontaneous murine T cell lymphoma (LB) that expresses LFA-1 adhesion molecules. The adhesion molecules were identified by fluorocytometry and immunoprecipitation with anti-CD18 mAb (M18/2). Subcutaneously inoculated LB lymphoma rapidly infiltrated the spleen and the lymph nodes, as indicated by histologic examination and [3H]thymidine incorporation assay of proliferating LB cells derived from the invaded organs. The normal organization of the lymphoid organs was totally effaced by the infiltrating LB cells. Intravenous injection of anti-CD18 mAb, protein G-purified anti-CD18 mAb, or its F(ab')2 fragments (but not irrelevant control mAb) blocked th...

Hyaluronan in Cancer Biology, 2009

ABSTRACT Tumor progression is substantially dependent on network of multiple factors, including a... more ABSTRACT Tumor progression is substantially dependent on network of multiple factors, including adhesion and homing molecules, which support the malignant metastatic spread. CD44, one of the adhesion/homing molecules, has attracted much attention not only because it is expressed on many types of tumors, but also owing to its numerous functions, such as supporting cell migration and transmitting survival signals, thereby being pro-oncogenic by nature. We have used the mouse malignant LB lymphoma cell line as a model for comprehensive in vitro and in vivo analyses of the interaction between CD44 and hyaluronic acid (HA), and its relevance to tumor dissemination. The in vitro studies revealed that LB cells could not bind HA, either under static or dynamic (i.e., shear flow) conditions, unless their CD44 is activated by phorbol ester, deglycosylated (to increase the CD44 positive net charge) or transfected with CD44 variants. In parallel, in vivo experiments showed that LB cell dissemination could be controlled by injection of anti-CD44 monoclonal antibodies or hyaluronidase. Furthermore, LB cells transfected with CD44v4-v10 variant, rather than standard CD44, displayed enhanced invasion of the peripheral lymph nodes. This effect was completely lost if the HA binding site of CD44 were mutated. LB cell accumulation in the lymph nodes is caused by enhanced migration via the afferent lymphatics rather than by accelerated proliferation within the lymph node. This information can be exploited to tailor a "therapeutic suit" that should be maximally effective in inducing tumor resistance, while minimizing destructive side effects.

Journal of immunology (Baltimore, Md. : 1950), Jan 15, 1995

Similar to activated T cells, LB T cell lymphoma expresses the CD44 cell surface Ag. In addition,... more Similar to activated T cells, LB T cell lymphoma expresses the CD44 cell surface Ag. In addition, the vast majority of LB cells also express the beta 2 (CD18) and alpha L (CD11a) chains of LFA-1 integrin. In view of the finding that anti-CD18 mAb blocked spleen, but not lymph node invasion by LB cells inoculated s.c. into BALB/c mice, we tested the ability of anti-CD44 mAb (IM 7.8.1) to block the infiltration of LB cells into the lymph nodes. We found that, as opposed to anti-CD18 mAb, anti-CD44 mAb, as well as its F(ab')2 or Fab fragment, prevented lymph node infiltration but had no effect on spleen invasion. This conclusion was based on histologic examination and [3H]thymidine incorporation into proliferating LB cells invading the lymphoid organs. Histologic analysis further demonstrated that LB cells invade the lymph node via the afferent lymphatics. The surface expression of CD44 molecules on LB cells was enhanced after PMA activation. PMA activation also enabled in vitro bi...

European Journal of Pharmacology

Reproduction, Fertility and Development

The possibility of maturing human primordial follicles in vitro would assist fertility restoratio... more The possibility of maturing human primordial follicles in vitro would assist fertility restoration without the danger of reseeding malignancies. Leukaemia inhibitory factor (LIF) and certain culture matrices may promote human follicular growth. The present study compared human primordial follicular growth on novel culture matrices, namely human recombinant vitronectin (hrVit), small intestine submucosa (SIS), alginate scaffolds and human recombinant virgin collagen bioengineered in tobacco plant lines (CollPlant). The frozen–thawed ovarian samples that were used had been obtained from girls or young women undergoing fertility preservation. In the first part of the study, 20 samples were cultured for 6 days on hrVit or SIS with basic culture medium alone or supplemented with one of two concentrations of LIF (10 ng mL–1 and 100 ng mL–1), with and without LIF-neutralising antibody. In the second part of the study, 15 samples were cultured for 6 days on alginate scaffolds or CollPlant m...

Reproductive BioMedicine Online, 2016

Dr Lande has participated in many clinical infertility studies and has considerable experience in... more Dr Lande has participated in many clinical infertility studies and has considerable experience in training medical students. He researches the effects of cyclophosphamide metabolites on primordial ovarian follicles in vitro. KEY MESSAGE Cyclophosphamide metabolites seem to enhance recruitment and activation of dormant primordial follicles in human ovarian tissue in vitro thus 'burning out' the ovarian reserve. This phenomenon may explain the specific toxicity of cyclophosphamide to human ovarian tissue. Developing a method to prevent follicular recruitment may possibly eliminate the toxic effect.

Clinical Immunology and Immunopathology, Apr 30, 1991

An immunogenic protein with an identical M, (64 kDa) was isolated from syngeneic concanavalin A-i... more An immunogenic protein with an identical M, (64 kDa) was isolated from syngeneic concanavalin A-induced lymphoblasts (synCon A-blasts) and YAC lymphoma cells, both derived from A mice. The 64-kDa protein was purified by a sequence of biochemical steps: Sephadex G-100 gel filtration, ion-exchange chromatography in a fast protein liquid chromatography system, Con A-Sepharose affinity chromatography, and preparative gel electrophoresis. The immunogenic fraction isolated in each step was moved to the next one, and so on. The immunogenicity of the separated fractions was measured by a lymph node proliferation (LNP) assay, which is indicative of a delayed-type hypersensitivity response. For instance, the final 64-kDa isolated protein of the synCon A-blasts induced an efftcient LNP response in A mice which was detected after challenge with the final 64-kDa isolated protein of YAC cells. In addition to their identical molecular weight, both proteins were eluted at the same ionic strength and both expressed afftnity to Con A-Sepharose beads, suggesting that they were glycosilated. Similar 64-kDa proteins were isolated by a different purification procedure, which was performed in the presence of protease inhibitors. excluding the possibility that the final antigen was an autodigested product. As the 64-kDa protein is immunogenic in the syngeneic host, it may be employed as a immunotherapeutic reagent against the original tumor and perhaps against other tumors expressing the same antigen. Cl I991 Academtc Presc. Inc.

Dermato-Endocrinology, 2016

Several inflammatory mediators increase calcitriol production by epidermal keratinocytes. In turn... more Several inflammatory mediators increase calcitriol production by epidermal keratinocytes. In turn calcitriol attenuates the keratinocyte inflammatory response. Since the effect of the in-situ generated calcitriol depends also on the sensitivity to the hormone we studied the effect of inflammatory cytokines on the response of HaCaT human keratinocytes to calcitriol by examining the expression and transcriptional activity of VDR. Treatment with TNF, but not with IL-1b or interferon g, increased VDR protein level, while decreasing the level of its heterodimerization partner RXRa. This was associated with increased VDR mRNA levels. c-Jun N-terminal kinase, but not P38 MAPK or NFkB, was found to participate in the upregulation of VDR by TNF. The functional significance of the modulation of VDR and RXRa levels by TNF is manifested by increased induction of VDR target gene CYP24A1 by calcitriol. Calcitriol, in turn, inhibited the enhanced expression of VDR by TNF. In conclusion, the inflammatory cytokine TNF increases the response of keratinocytes to calcitriol through upregulation of its receptor VDR, which in turn is subject to negative feedback by the hormone accelerating the return of the keratinocyte vitamin D system to its basal activity. We surmise that the increased generation and sensitivity to calcitriol in keratinocytes play a role in the resolution of epidermal inflammation.

PLoS ONE, 2013

Popeye domain containing1 (Popdc1), also named Bves, is an evolutionary conserved membrane protei... more Popeye domain containing1 (Popdc1), also named Bves, is an evolutionary conserved membrane protein. Despite its high expression level in the heart little is known about its membrane localization and cardiac functions. The study examined the hypothesis that Popdc1 might be associated with the caveolae and play a role in myocardial ischemia tolerance. To address these issues, we analyzed hearts and cardiomyocytes of wild type and Popdc1-null mice. Immunoconfocal microscopy revealed co-localization of Popdc1 with caveolin3 in the sarcolemma, intercalated discs and T-tubules and with costameric vinculin. Popdc1 was co-immunoprecipitated with caveolin3 from cardiomyocytes and from transfected COS7 cells and was co-sedimented with caveolin3 in equilibrium density gradients. Caveolae disruption by methyl-b-cyclodextrin or by ischemia/reperfusion (I/R) abolished the cellular co-localization of Popdc1 with caveolin3 and modified their density cosedimentation. The caveolin3-rich fractions of Popdc1-null hearts redistributed to fractions of lower buoyant density. Electron microscopy showed a statistically significant 70% reduction in caveolae number and a 12% increase in the average diameter of the remaining caveolae in the mutant hearts. In accordance with these changes, Popdc1-null cardiomyocytes displayed impaired [Ca +2 ] i transients, increased vulnerability to oxidative stress and no pharmacologic preconditioning. In addition, induction of I/R injury to Langendorff-perfused hearts indicated a significantly lower functional recovery in the mutant compared with wild type hearts while their infarct size was larger. No improvement in functional recovery was observed in Popdc1-null hearts following ischemic preconditioning. The results indicate that Popdc1 is a caveolaeassociated protein important for the preservation of caveolae structural and functional integrity and for heart protection.

Mechanisms of Development, 1996

Mouse developmental kinase 4 (MDK4), a novel receptor tyrosine kinase (RTK), was identified via d... more Mouse developmental kinase 4 (MDK4), a novel receptor tyrosine kinase (RTK), was identified via degenerate primer screening of mouse embryo cDNA. The mRNA encoding this RTK was found only in skeletal muscle of mouse embryos and the maternal decidua. Northern blot analysis predicted an mRNA transcript size of 6.1 kb. The amino acid sequence is most closely related to Torpedo RTK. Analysis of mRNA and protein content of C2C12 cells at different stages of the differentiation process revealed increasing levels of MDK4 during this process. Immunofluorescence data indicated that MDK4 protein production begins with myoblasts elongation and is maintained throughout myotube formation. MDK4 transcripts were furthermore detected in the decidua tissue surrounding young embryos. Since decidua cells also form syncytia, it is possible that MDK4 is involved in the formation, regulation, and/or maintenance of the polynucleated state.

Journal of Biological Chemistry, 2002

Experimental Hematology, 2009

Objective. Cloned placenta immunoregulatory ferritin (PLIF) contains a novel, nonferritin bioacti... more Objective. Cloned placenta immunoregulatory ferritin (PLIF) contains a novel, nonferritin bioactive domain (C-48) with immunodulatory activity. We documented that treatment of whole human bone marrow cells with PLIF and its subcloned C48 proteins resulted in myeloid progenitor cell growth and differentiation and T-cell suppression via an effect on the cytokine network. We tested whether this differential effect supports allogeneic bone marrow transplantation with long-lasting tolerance without any further treatments. Materials and Methods. Splenocyte-enriched C3H (H2 k) whole bone marrow was transplanted into C57Bl (H2 b) recipients after total body irradiation. Recipients were injected with recombinant C48 (3mg/kg, intraperitoneal) for 21 days or with glutathione S-transferase. Animals were monitored for survival, chimerism, and clinical signs of graft-vs-host disease (GVHD). Next, chimera whole bone marrow was transplanted to secondary myeloablated C57Bl (H2 b) hosts without treatment. Results. Mice that received C48 treatment following allogeneic splenocyte-enriched bone marrow transplantation demonstrated full-donor chimerism without GVHD mortality, and normal blood cell counts in 75% of recipients. Secondary transplants from the full chimera to myeloblated C57Bl hosts showed 100% engraftment, no GVHD mortality, and no impairment in the long-term hematopoietic reconstitution potential. Allogeneic response of spleen cells from secondary chimeras against donor C3H (H2 k) and recipient C57Bl (H2 b) were similar to syngeneic response, whereas reactivity to third party (DBA H2 d) was significantly enhanced. Conclusions. Findings of this study provide the proof of concept that C48da novel, single, bifunctional therapeutic modality enabled successful allogeneic, unmanipulated bone marrow transplantation without GVHD, and with lasting specific tolerance.

The Journal of Biological Chemistry, Apr 12, 2002

International Immunology

ABSTRACT

Proceedings of the National Academy of Sciences, 1996

ERK6, a mitogen-activated protein (MAP) kinase-related serine/threonine kinase, is highly express... more ERK6, a mitogen-activated protein (MAP) kinase-related serine/threonine kinase, is highly expressed in human skeletal muscle and appears to function as a signal transducer during differentiation of myoblasts to myotubes. In transfected 293 cells, activation of the 45-kDa enzyme results in tyrosine-phosphorylated 46- and 56-kDa forms, which phosphorylate myelin basic protein. Overexpression of wild-type ERK6 or the inactive mutant Y185F has no effect on fibroblast and myoblast proliferation, but it enhances or inhibits C2C12 cell differentiation to myotubes, respectively. Our findings suggest ERK6 to be a tissue-specific, differentiation signal-transducing factor that is connected to phosphotyrosine-mediated signaling pathways distinct from those activating other members of the MAP kinase family such as LRK1 and ERK2.

FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2003

Recently, we reported the cloning and preliminary characterization of a novel human immunomodulat... more Recently, we reported the cloning and preliminary characterization of a novel human immunomodulator named PLIF (placenta immunomodulatory ferritin). PLIF has a unique molecular structure, which is composed of a ferritin heavy chain-like domain and a novel cytokine-like domain called C48. Both intact molecule and C48 inhibit T cell proliferation following allogeneic or anti-CD3 stimuli. PLIF is localized at the fetal-maternal interface of human placenta and might play a role in down-modulating the maternal immune reaction toward the embryo. The inhibitory effect of PLIF on T cell activation can be direct, indirect through cytokine mediators, or both. In the present study we investigated the possible indirect effects of PLIF by using its bioactive domain C48. Measurement of various cytokines revealed that C48, predominantly, induce pronounced and rapid IL-10 production in monocytes, which is immune activation-independent. Further, we discovered that C48-induced IL-10 production is med...

Neoplasia, 2014

Immune tolerance mechanisms supporting normal human pregnancy are exploited by breast cancer and ... more Immune tolerance mechanisms supporting normal human pregnancy are exploited by breast cancer and other malignancies. We cloned from human placenta and breast cancer cells the novel human immunomodulator named placenta immunosuppressive ferritin (PLIF). PLIF is composed of a ferritin heavy chain-like domain and a novel cytokine-like domain, named C48. Both intact PLIF and C48 inhibit T cell proliferation. Blocking PLIF by specific antibodies in a tolerant breast cancer model in nude mice resulted in tumor cell apoptosis and rejection. This prompted us to study active immune preventive strategies targeting PLIF activity. Currently, we report on the design and synthesis of the novel C24D polypeptide, which inhibits the binding of PLIF to T cells and therefore inhibits the immune suppressive effect of PLIF. The effect of C24D on the generation of anti-breast cancer cytotoxic T lymphocytes (CTLs) was studied in vitro in cultures of MCF-7 (HLA-A2(+)) or T47D (HLA-A2(-)) breast cancer cells incubated with peripheral blood mononuclear cells (PBMCs) from healthy blood donors. We found that C24D treatment exclusively induced development of CTLs. On reactivation by their specific target cells, the CTLs secreted interferon-γ and induced target apoptosis. Anti-MCF-7 CTLs were cross-cytotoxic to MDA-MB-231 (HLA-A2(+)) triple-negative breast cancer but not to T47D. Moreover, C24D treatment in vivo inhibited the growth of MCF-7 tumors engrafted in immune-compromised nude mice transfused with naïve allogeneic human PBMCs. Our results demonstrate that C24D treatment breakdown breast cancer induced tolerance enabling the initiation of effective anti-tumor immune response.