excitotoxic-stimulation-brain-microslices-as-an-vitro-model

Excitotoxic Stimulation of Brain Microslices as an <em>In vitro</em> Model of Stroke

Examining molecular mechanisms involved in neuropathological conditions, such as ischemic stroke, can be difficult when using whole animal systems. As ...

The University of Newcastle

Chlamydia trachomatis is a pathogen of the genital tract and ocular epithelium. Infection is established by the binding of the metabolically inert elementary body (EB) to epithelial cells. These are taken up by endocytosis into a membrane-bound vesicle termed an inclusion. The inclusion avoids fusion with host lysosomes, and the EBs differentiate into the metabolically active reticulate body (RB), which replicates by binary fission within the protected environment of the inclusion. During the extracellular EB stage of the C. trachomatis life cycle, antibody present in genital tract or ocular secretions can inhibit infection both in vivo and in tissue culture. The RB, residing within the intracellular inclusion, is not accessible to antibody, and resolution of infection at this stage requires a cell-mediated immune response mediated by gamma interferon-secreting Th1 cells. Thus, an ideal vaccine to protect against C. trachomatis genital tract infection should induce both antibody (immunoglobulin A [IgA] and IgG) responses in mucosal secretions to prevent infection by chlamydial EB and a strong Th1 response to limit ascending infection to the uterus and fallopian tubes. In the present study we show that transcutaneous immunization with major outer membrane protein (MOMP) in combination with both cholera toxin and CpG oligodeoxynucleotides elicits MOMP-specific IgG and IgA in vaginal and uterine lavage fluid, MOMP-specific IgG in serum, and gamma interferon-secreting T cells in reproductive tract-draining caudal and lumbar lymph nodes. This immunization protocol resulted in enhanced clearance of C. muridarum (C. trachomatis, mouse pneumonitis strain) following intravaginal challenge of BALB/c mice.

Transcutaneous immunization with combined cholera toxin and CpG adjuvant protects against Chlamydia muridarum genital tract infection.

Successful control of sexually transmitted diseases (STDs) through vaccination will require the development of vaccine strategies that target protective immunity to both the female and male reproductive tracts (MRT). In the male, the immune privileged nature of the male reproductive tract provides a barrier to entry of serum immunoglobulins into the male reproductive ducts, thereby preventing the induction of protective immunity using conventional injectable vaccination techniques. In this study we investigated the potential of intranasal (IN) immunization to elicit anti-chlamydial immunity in BALB/c male mice. Intranasal immunization with Chlamydia muridarum major outer membrane protein (MOMP) admixed with cholera toxin (CT) resulted in high levels of MOMP-specific IgA in prostatic fluids (PF) and MOMP-specific IgA-secreting cells in the prostate. Prostatic fluid IgA inhibited in vitro infection of McCoy cells with C. muridarum. Using RT-PCR we also show that mRNA for the polymeric immunoglobulin receptor (PIgR), which transports IgA across mucosal epithelia, is expressed only in the prostate but not in other regions of the male reproductive ducts upstream of the prostate. These data suggest that using intranasal immunization to target IgA to the prostate may protect males against STDs while at the same time maintaining the state of immune privilege within the MRT.

Intranasal immunization with C. muridarum major outer membrane protein (MOMP) and cholera toxin elicits local production of neutralising IgA in the prostate.

Chlamydia pneumoniae causes a range of respiratory infections including bronchitis, pharyngitis and pneumonia. Infection has also been implicated in exacerbation/initiation of asthma and chronic obstructive pulmonary disease (COPD) and may play a role in atherosclerosis and Alzheimer's disease. We have used a mouse model of Chlamydia respiratory infection to determine the effectiveness of intranasal (IN) and transcutaneous immunization (TCI) to prevent Chlamydia lung infection. Female BALB/c mice were immunized with chlamydial major outer membrane protein (MOMP) mixed with cholera toxin and CpG oligodeoxynucleotide adjuvants by either the IN or TCI routes. Serum and bronchoalveolar lavage (BAL) were collected for antibody analysis. Mononuclear cells from lung-draining lymph nodes were stimulated in vitro with MOMP and cytokine mRNA production determined by real time PCR. Animals were challenged with live Chlamydia and weighed daily following challenge. At day 10 (the peak of infection) animals were sacrificed and the numbers of recoverable Chlamydia in lungs determined by real time PCR. MOMP-specific antibody-secreting cells in lung tissues were also determined at day 10 post-infection. Both IN and TCI protected animals against weight loss compared to non-immunized controls with both immunized groups gaining weight by day 10-post challenge while controls had lost 6% of body weight. Both immunization protocols induced MOMP-specific IgG in serum and BAL while only IN immunization induced MOMP-specific IgA in BAL. Both immunization routes resulted in high numbers of MOMP-specific antibody-secreting cells in lung tissues (IN>TCI). Following in vitro re-stimulation of lung-draining lymph node cells with MOMP; IFNgamma mRNA increased 20-fold in cells from IN immunized animals (compared to non-immunized controls) while IFNgamma levels increased 6- to 7-fold in TCI animals. Ten days post challenge non-immunized animals had >7,000 IFU in their lungs, IN immunized animals <50 IFU and TCI immunized animals <1,500 IFU. Thus, both intranasal and transcutaneous immunization protected mice against respiratory challenge with Chlamydia. The best protection was obtained following IN immunization and correlated with IFNgamma production by mononuclear cells in lung-draining LN and MOMP-specific IgA in BAL.

Comparison of intranasal and transcutaneous immunization for induction of protective immunity against Chlamydia muridarum respiratory tract infection.

Breast cancer is the most commonly diagnosed malignancy in women worldwide. Metastatic development is associated with poor prognosis and current therapies provide only limited success. Virotherapy is an emerging strategy for the treatment of cancer that utilizes both replication-competent and genetically modified viruses to selectively kill tumor cells. We have previously shown that Coxsackievirus A21 (CVA21), a wild-type common-cold producing enterovirus, is an effective oncolytic agent against human melanoma xenografts in vivo. CVA21 specifically targets and lytically infects susceptible cells expressing the CVA21 cellular receptors, intercellular adhesion molecule-1 (ICAM-1) and/or decay-accelerating factor (DAF). Herein, the efficacy of CVA21 as a therapeutic agent against human breast cancer was investigated both in vitro and in vivo. Flow cytometric analysis revealed that the human breast cancer cell lines examined expressed significantly elevated levels of surface ICAM-1 and DAF compared to normal breast cell lines, and that all cancerous lines were more susceptible to lytic infection by CVA21 than the normal cells. Through the use of subcutaneous (T47D cells) and orthotopic (MDA-MB-231-luc cells) xenograft SCID mouse models it was demonstrated that a single intravenous injection of CVA21 produced significant regression of pre-established tumors in vivo, as well as targeting and elimination of metastases in the orthotopic model. Taken together, these findings highlight the exciting potential of CVA21 as a therapeutic agent against both primary and metastatic human breast cancer.

Systemic targeting of metastatic human breast tumor xenografts by Coxsackievirus A21.

CaMKII (calcium/calmodulin-stimulated protein kinase II) is a multifunctional protein kinase that regulates normal neuronal function. CaMKII is regulated by multi-site phosphorylation, which can alter enzyme activity, and targeting to cellular microdomains through interactions with binding proteins. These proteins integrate CaMKII into multiple signalling pathways, which lead to varied functional outcomes following CaMKII phosphorylation, depending on the identity and location of the binding partner. A new phosphorylation site on CaMKII (Thr253) has been identified in vivo. Thr253 phosphorylation controls CaMKII purely by targeting, does not effect enzyme activity, and occurs in response to physiological and pathological stimuli in vivo, but only in CaMKII molecules present in specific cellular locations. This new phosphorylation site offers a potentially novel regulatory mechanism for controlling functional responses elicited by CaMKII that are restricted to specific subcellular locations and/or certain cell types, by controlling interactions with proteins that are expressed in the cell at that location.

Regulation of CaMKII in vivo: the importance of targeting and the intracellular microenvironment.

Calcium/calmodulin-stimulated protein kinase II (CaMKII) is an important mediator of synaptic function that is regulated by multi-site phosphorylation and targeting through interactions with proteins. A new phosphorylation site at Thr253 has been identified in vivo, that does not alter CaMKII activity, but does alter CaMKII function through interactions with binding proteins. To identify these proteins, as well as to examine the specific effects following Thr253 or Thr286 phosphorylation on these interactions, we developed an in vitro overlay binding assay. We demonstrated that the interaction between CaMKII and its binding proteins was altered by the phosphorylation state of both the CaMKII and the partner, and identified a CaMKII-specific sequence that was responsible for the interaction between CaMKII and two interacting proteins. By comparing CaMKII binding profiles in tissue and cell extracts, we demonstrated that the CaMKII binding profiles varied with cell type, and also showed that overexpression of a CaMKII Thr253 phospho-mimic mutant in human neuroblastoma and breast cancer cells dramatically altered the morphology and growth rates when compared to overexpression of non-phosphorylated CaMKII. This data highlights the importance of the microenvironment in regulating CaMKII function, and describes a potentially new mechanism by which the functions of CaMKII can be regulated.

Regulation of CaMKII by phospho-Thr253 or phospho-Thr286 sensitive targeting alters cellular function.

Virotherapy is an emerging strategy for the treatment of cancer that utilizes both replication-competent and genetically modified viruses to selectively kill tumor cells. We have previously shown that Coxsackievirus A21 (CVA21), a common-cold producing enterovirus, is an effective oncolytic agent against human melanoma, prostate, and breast cancer xenografts in vivo. CVA21 specifically targets and lytically infects susceptible cells expressing the CVA21 cellular receptors, intercellular adhesion molecule-1 (ICAM-1) and decay-accelerating factor (DAF). Herein, the efficacy of CVA21 administered in combination with doxorubicin hydrochloride as a new therapeutic regimen for cancer was investigated. Flow cytometric analysis demonstrated that the human breast, colorectal, and pancreatic cancer cell lines examined expressed moderate levels of surface ICAM-1 and DAF, whilst a normal breast cell line expressed only minimal levels. When CVA21 was combined with doxorubicin hydrochloride, synergistically enhanced cell death was observed when CVA21 was administered both simultaneously or 24 h prior to doxorubicin hydrochloride exposure. Doxorubicin hydrochloride had no effect on CVA21 replication. Through the use of an orthotopic (MDA-MB-231-luc) xenograft SCID mouse model of human breast cancer we showed that a single intravenous injection of CVA21 in combination with an intraperitoneal injection of doxorubicin hydrochloride resulted in significantly greater tumor reduction compared to either agent alone. Overall, these findings highlight the exciting potential of CVA21, administered in combination with doxorubicin hydrochloride, as a new therapeutic regimen for cancer.

Enhanced oncolysis mediated by Coxsackievirus A21 in combination with doxorubicin hydrochloride.

Many studies have implicated Ca²+ and calmodulin (CaM) as regulators of the cell cycle. Ca²+/CaM-stimulated proteins, including the family of multifunctional Ca²+/CaM-stimulated protein kinases (CaMK), have also been identified as mediators of cell cycle progression. CaMKII is the best-characterized member of this family, and is regulated by multi-site phosphorylation and targeting. Using pharmacological inhibitors that were believed to be specific for CaMKII, CaMKII has been implicated in every phase of the cell cycle. However, these 'specific' inhibitors also produce effects on other CaMKs. These additional effects are usually ignored, and the effects of the inhibitors are normally attributed to CaMKII without further investigation. Using new specific molecular techniques, it has become clear that CaMKI is an important regulator of G₁, whereas CaMKII is essential for regulating G₂/M and the metaphase-anaphase transition. If the mechanisms controlling these events can be fully elucidated, new targets for controlling proliferative diseases may be identified.

Controlling the cell cycle: the role of calcium/calmodulin-stimulated protein kinases I and II.

Calcium/calmodulin-stimulated protein kinases can be classified as one of two types - restricted or multifunctional. This family of kinases contains several structural similarities: all possess a calmodulin binding motif and an autoinhibitory region. In addition, all of the calcium/calmodulin-stimulated protein kinases examined in this chapter are regulated by phosphorylation, which either activates or inhibits their kinase activity. However, as the multifunctional calcium/calmodulin-stimulated protein kinases are ubiquitously expressed, yet regulate a broad range of cellular functions, additional levels of regulation that control these cell-specific functions must exist. These additional layers of control include gene expression, signaling pathways, and expression of binding proteins and molecular targeting. All of the multifunctional calcium/calmodulin-stimulated protein kinases examined in this chapter appear to be regulated by these additional layers of control, however, this does not appear to be the case for the restricted kinases.

The role of molecular regulation and targeting in regulating calcium/calmodulin stimulated protein kinases.

Different brain regions exhibit differing sensitivities to ischemia/excitotoxicity. Whether these differences are due to perfusion or intrinsic factors has not been established. Herein, we found no apparent association between sensitivity to ischemia/excitotoxicity and the level of expression or basal phosphorylation of calcium/calmodulin-stimulated protein kinase II (αCaMKII) or glutamate receptors. However, we demonstrated significant differences in CaMKII-mediated responses after ischemia/excitotoxic stimulation in striatum and cortex. In vivo ischemia and in vitro excitotoxic stimulation produced more rapid phosphorylation of Thr253-αCaMKII in striatum compared with cortex, but equal rates of Thr286-αCaMKII phosphorylation. Phosphorylation by CaMKII of Ser831-GluA1 and Ser1303-GluN2B occurred more rapidly in striatum than in cortex after either stimulus. The differences between brain regions in CaMKII activation and its effects were not accounted for by differences in the expression of αCaMKII, glutamate receptors, or density of synapses. These results implicate intrinsic tissue differences in Thr253-αCaMKII phosphorylation in the differential sensitivities of brain regions to ischemia/excitotoxicity.

αCaMKII is differentially regulated in brain regions that exhibit differing sensitivities to ischemia and excitotoxicity.

Calcium/calmodulin-stimulated protein kinase II (CaMKII) is a multi-functional serine/threonine protein kinase that controls a range of cellular functions, including proliferation. The biological properties of CaMKII are regulated by multi-site phosphorylation and targeting via interactions with specific proteins. To investigate the role specific CaMKII phosphorylation sites play in controlling cell proliferation and cell cycle progression, we examined phosphorylation of CaMKII at two sites (T253 and T286) at various stages of the cell cycle, and also examined the effects of overexpression of wild-type (WT), T286D phosphomimic, T253D phosphomimic and T253V phosphonull forms of CaMKIIα in MDA-MB-231 breast cancer and SHSY5Y neuroblastoma cells on cellular proliferation and cell cycle progression. We demonstrate herein that whilst there is no change in total CaMKII expression or T286 phosphorylation throughout the cell cycle, a marked dephosphorylation of CaMKII at T253 occurs during the G2 and/or M phases. Additionally, we show by molecular inhibition, as well as pharmacological activation, that protein phosphatase 2A (PP2A) is the phosphatase responsible for this dephosphorylation. Furthermore, we show that inducible overexpression of WT, T286D and T253V forms of CaMKIIα in MDA-MB-231 and SHSY5Y cells increases cellular proliferation, with no alteration in cell cycle profiles. By contrast, overexpression of a T253D phosphomimic form of CaMKIIα significantly decreases proliferation, and cells accumulate in mitosis, specifically in metaphase. Taken together, these results strongly suggest that the dephosphorylation of CaMKII at T253 is involved in controlling the cell cycle, specifically the metaphase-anaphase transition.

Kathryn A. Skelding

School of Biomedical Sciences and Pharmacy,
Hunter Medical Research Institute,
School of Biomedical Sciences and Pharmacy, Hunter Medical Research Institute

The University of Newcastle

Excitotoxic Stimulation of Brain Microslices as an In vitro Model of Stroke

Kathryn A. Skelding

School of Biomedical Sciences and Pharmacy,Hunter Medical Research Institute,School of Biomedical Sciences and Pharmacy, Hunter Medical Research Institute

The University of Newcastle

Excitotoxic Stimulation of Brain Microslices as an In vitro Model of Stroke

School of Biomedical Sciences and Pharmacy,
Hunter Medical Research Institute,
School of Biomedical Sciences and Pharmacy, Hunter Medical Research Institute