Caspase-1 level is higher in the scalp in androgenetic alopecia

BACKGROUND AND OBJECTIVES

Inflammasomes that activate caspase-1 govern the innate immune inflammatory response. Whether hair loss associated with androgenetic alopecia (AGA) involves caspase-1 activation is not known.

METHODS

Immunohistochemical staining for caspase-1 was performed on scalp tissue sections, and protein lysates were analyzed from individuals with AGA (no treatment), and individuals with AGA taking finasteride with apparent hair growth, individuals with AGA taking finasteride without noted hair growth, and normal controls. In vitro studies of human keratinocytes were conducted to establish effects of finasteride, dihydrotestosterone (DHT), and testosterone on caspase-1 levels using immunoblot analysis.

RESULTS

Caspase-1 is expressed in normal human adult epidermal keratinocytes. Caspase-1 expression is greater in men with AGA. In contrast, in men taking finasteride, caspase-1 levels were lower and were similar to those in normal controls. In vitro studies showed that keratinocytes treated with finasteride in combination with testosterone or DHT resulted in a significant decrease in caspase-1 expression.

CONCLUSION

In vivo and in vitro finasteride treatment resulted in lower caspase-1 expression, supporting the idea that androgens influence innate immunity involved in the hair cycle in AGA. These findings may provide a basis for development of novel treatments for inflammatory skin and hair diseases.

5-Hydroxytryptamine 5HT2C receptors form a protein complex with N-methyl-D-aspartate GluN2A subunits and activate phosphorylation of Src protein to modulate motoneuronal depolarization

N-Methyl-D-aspartate (NMDA)-gated ion channels are known to play a critical role in motoneuron depolarization, but the molecular mechanisms modulating NMDA activation in the spinal cord are not well understood. This study demonstrates that activated 5HT2C receptors enhance NMDA depolarizations recorded electrophysiologically from motoneurons. Pharmacological studies indicate involvement of Src tyrosine kinase mediates 5HT2C facilitation of NMDA. RT-PCR analysis revealed edited forms of 5HT2C were present in mammalian spinal cord, indicating the availability of G-protein-independent isoforms. Spinal cord neurons treated with the 5HT2C agonist MK 212 showed increased Src(Tyr-416) phosphorylation in a dose-dependent manner thus verifying that Src is activated after treatment. In addition, 5HT2C antagonists and tyrosine kinase inhibitors blocked 5HT2C-mediated Src(Tyr-416) phosphorylation and also enhanced NMDA-induced motoneuron depolarization. Co-immunoprecipitation of synaptosomal fractions showed that GluN2A, 5HT2C receptors, and Src tyrosine kinase form protein associations in synaptosomes. Moreover, immunohistochemical analysis demonstrated GluN2A and 5HT2C receptors co-localize on the processes of spinal neurons. These findings reveal that a distinct multiprotein complex links 5-hydroxytryptamine-activated intracellular signaling events with NMDA-mediated functional activity.

Astrogliosis involves activation of retinoic acid-inducible gene-like signaling in the innate immune response after spinal cord injury

Spinal cord injury (SCI) induces a glial response in which astrocytes become activated and produce inflammatory mediators. The molecular basis for regulation of glial-innate immune responses remains poorly understood. Here, we examined the activation of retinoic acid-inducible gene (RIG)-like receptors (RLRs) and their involvement in regulating inflammation after SCI. We show that astrocytes express two intracellular RLRs: RIG-I and melanoma differentiation-associated gene 5. SCI and stretch injury of cultured astrocytes stimulated RLR signaling as determined by phosphorylation of interferon regulatory factor 3 (IRF3) leading to production of type I interferons (IFNs). RLR signaling stimulation with synthetic ribonucleic acid resulted in RLR activation, phosphorylation of IRF3, and increased expression of glial fibrillary acidic protein (GFAP) and vimentin, two hallmarks of reactive astrocytes. Moreover, mitochondrial E3 ubiquitin protein ligase 1, an RLR inhibitor, decreased production of GFAP and vimentin after RIG-I signaling stimulation. Our findings identify a role for RLR signaling and type I IFN in regulating astrocyte innate immune responses after SCI.

Heightened inflammasome activation is linked to age-related cognitive impairment in Fischer 344 rats

Background

Members of the mammalian nucleotide binding domain, leucine-rich repeat (LRR)-containing receptor (NLR) family of proteins are key modulators of innate immunity regulating inflammation. Our previous work has shown that among the members of this family, NLRP1/NALP1, present in neurons, plays a crucial role in inflammasome formation and the production of the inflammatory cytokines interleukin (IL) -1β and IL-18 after various types of central nervous system injury.

Results

We investigated whether age-related cognitive decline may involve a heightened inflammatory response associated with activation of the NLRP1 inflammasome in the hippocampus. Young (3 months) and aged (18 months) male Fischer 344 rats were tested in a spatial acquisition task via Morris water maze. Following behavioral testing, hippocampal lysates were assayed for expression of NLRP1 inflammasome components and inflammatory cytokines. Hippocampal lysates from aged rats showed significantly higher levels of NLRP1 inflammasome constituents, caspase-1, caspase-11, the purinergic receptor P2X7, pannexin-1 and X-linked inhibitor of apoptosis (XIAP) than lysates from younger animals. Following treatment with probenecid, an inhibitor or pannexin-1, aged animals demonstrated reduction in inflammasome activation and improvement in spatial learning performance.

Conclusions

Our behavioral findings are consistent with increases in IL-1β and IL-18 that have been previously shown to correlate with spatial learning deficits. Probenecid reduced activated caspase-1 and ameliorated spatial learning deficits in aged rats. Thus, aging processes stimulate activation of the NLRP1 inflammasome and secretion of IL-1β and IL-18 that may contribute to age-related cognitive decline in the growing elderly population. Moreover, probenecid may be potentially useful as a therapy to improve cognitive outcomes in the aging population.

In vivo electroporation and non-protein based screening assays to identify antibodies against native protein conformations

In vivo electroporation has become a gold standard method for DNA immunization. The method assists the DNA entry into cells, results in expression and the display of the native form of antigens to professional cells of the immune system, uses both arms of immune system, has a built-in adjuvant system, is relatively safe, and is cost-effective. However, there are challenges for achieving an optimized reproducible process for eliciting strong humoral responses and for the screening of specific immune responses, in particular, when the aim is to mount humoral responses or to generate monoclonal antibodies via hybridoma technology. Production of monoclonal antibodies demands generation of high numbers of primed B and CD4 T helper cells in lymphoid organs needed for the fusion that traditionally is achieved by a final intravenous antigen injection. The purified antigen is also needed for screening of hundreds of clones obtained upon fusion of splenocytes. Such challenges make DNA vaccination dependent on purified proteins. Here, we have optimized methods for in vivo electroporation, production, and use of cells expressing the antigen and an in-cell Western screening method. These methods resulted in (1) reproducibly mounting robust humoral responses against antigens with different cell localizations, and (2) the ability to screen for antigen eliminating a need for protein/antigen purification. This process includes optimized parameters for in vivo electroporation, the use of transfected cells for final boost, and mild fixation/permeabilization of cells for screening. Using this process, upon two vaccinations via in vivo electroporation (and final boost), monoclonal antibodies against nucleus and cytoplasmic and transmembrane proteins were achieved.

Neuroprotective effects of bone morphogenetic protein 7 (BMP7) treatment after spinal cord injury

Bone morphogenetic protein 7 (BMP7) has been shown to ameliorate reduced dendritic growth induced by glutamate excitotoxicity in neuronal tissue cultures and/or provide an enhancement of functional recovery in central nervous system (CNS) injury. BMP7 expression is modulated by spinal cord injury (SCI), but the molecular mechanisms involved in neuroprotection have not been clearly defined. Here, we show that BMP7 treatment of rats subjected to mild cervical SCI significantly increased the pro-survival mitogen-activated protein kinase-38 (MAPK-38) pathway and levels of N-methyl-D-aspartate receptor 1 (NMDAR-1) resulting in a significant increase in neuronal sparing in the ventral horn of the spinal cord. Moreover, BMP7 was neuroprotective against glutamate-mediated excitotoxicity in cultured cortical neurons. These studies show that BMP7 administration may be used as a therapeutic strategy to reduce the damaging excitotoxic effects following SCI.

Therapeutic neutralization of the NLRP1 inflammasome reduces the innate immune response and improves histopathology after traumatic brain injury

Traumatic brain injury elicits acute inflammation that in turn exacerbates primary brain damage. A crucial part of innate immunity in the immune privileged central nervous system involves production of proinflammatory cytokines mediated by inflammasome signaling. Here, we show that the nucleotide-binding, leucine-rich repeat pyrin domain containing protein 1 (NLRP1) inflammasome consisting of NLRP1, caspase-1, caspase-11, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), the X-linked inhibitor of apoptosis protein, and pannexin 1 is expressed in neurons of the cerebral cortex. Moderate parasagittal fluid-percussion injury (FPI) induced processing of interleukin-1beta, activation of caspase-1, cleavage of X-linked inhibitor of apoptosis protein, and promoted assembly of the NLRP1 inflammasome complex. Anti-ASC neutralizing antibodies administered immediately after fluid-percussion injury to injured rats reduced caspase-1 activation, X-linked inhibitor of apoptosis protein cleavage, and processing of interleukin-1beta, resulting in a significant decrease in contusion volume. These studies show that the NLRP1 inflammasome constitutes an important component of the innate central nervous system inflammatory response after traumatic brain injury and may be a novel therapeutic target for reducing the damaging effects of posttraumatic brain inflammation.

Sex differences in XIAP cleavage after traumatic brain injury in the rat

Sex influences histological and behavioral outcomes following traumatic brain injury (TBI), but the underlying sex-dependent pathomechanisms regulating outcome measures remain poorly defined. Here, we investigated the TBI-induced regulation of the X-linked inhibitor of apoptosis protein (XIAP) that, in addition to suppressing cell death by inhibition of caspases, is involved in signaling cascades, including immune regulation and cell migration. Since estrogen has been shown to have anti-apoptotic properties, we specifically examined sex differences and the influence of estrogen on XIAP processing after TBI. Sprague-Dawley male (TBI-M), female (TBI-F), ovariectomized female (TBI-OVX) and ovariectomized females supplemented with estrogen (TBI-OVX+EST) were subjected to moderate (1.7-2.2atm) fluid percussion (FP) injury. Animals were sacrificed 24h after FP injury; cortical tissue (ipsilateral and contralateral) was dissected and analyzed for XIAP processing by immunoblot analysis (n=6-7/group) or confocal microscopy (n=2-3/group). Significant differences in XIAP cleavage products in the ipsilateral cortex were found between groups (p<0.03). Post hoc analysis showed an increase in XIAP processing in both TBI-F and TBI-OVX+EST compared to TBI-M and TBI-OVX (p<0.05), indicating that more XIAP is cleaved following injury in intact females and TBI-OVX+EST than in TBI-M and TBI-OVX groups. Co-localization of XIAP within neurons also demonstrated sex-dependent changes. Based on these data, it appears that the processing of XIAP after injury is different between males and females and may be influenced by exogenous estrogen treatment.

The pannexin 1 channel activates the inflammasome in neurons and astrocytes

The inflammasome is a multiprotein complex involved in innate immunity. Activation of the inflammasome causes the processing and release of the cytokines interleukins 1beta and 18. In primary macrophages, potassium ion flux and the membrane channel pannexin 1 have been suggested to play roles in inflammasome activation. However, the molecular mechanism(s) governing inflammasome signaling remains poorly defined, and it is undetermined whether these mechanisms apply to the central nervous system. Here we show that high extracellular potassium opens pannexin channels leading to caspase-1 activation in primary neurons and astrocytes. The effect of K(+) on pannexin 1 channels was independent of membrane potential, suggesting that stimulation of inflammasome signaling was mediated by an allosteric effect. The activation of the inflammasome by K(+) was inhibited by the pannexin 1 channel blocker probenecid, supporting a role of pannexin 1 in inflammasome activation. Co-immunoprecipitation of neuronal lysates indicates that pannexin 1 associates with components of the multiprotein inflammasome complex, including the P2X7 receptor and caspase-1. Moreover antibody neutralization of the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) blocked ATP-induced cell death in oocytes co-expressing P2X7 receptor and pannexin 1. Thus, in contrast to macrophages and monocytes in which low intracellular K(+) has been suggested to trigger inflammasome activation, in neural cells, high extracellular K(+) activates caspase-1 probably through pannexin 1.

A novel protein complex in membrane rafts linking the NR2B glutamate receptor and autophagy is disrupted following traumatic brain injury

Hyperactivation of N-methyl-D-aspartate receptors (NRs) is associated with neuronal cell death induced by traumatic brain injury (TBI) and many neurodegenerative conditions. NR signaling efficiency is dependent on receptor localization in membrane raft microdomains. Recently, excitotoxicity has been linked to autophagy, but mechanisms governing signal transduction remain unclear. Here we have identified protein interactions between NR2B signaling intermediates and the autophagic protein Beclin-1 in membrane rafts of the normal rat cerebral cortex. Moderate TBI induced rapid recruitment and association of NR2B and pCaMKII to membrane rafts, and translocation of Beclin-1 out of membrane microdomains. Furthermore, TBI caused significant increases in expression of key autophagic proteins and morphological hallmarks of autophagy that were significantly attenuated by treatment with the NR2B antagonist Ro 25-6981. Thus, stimulation of autophagy by NR2B signaling may be regulated by redistribution of Beclin-1 in membrane rafts after TBI.

The inflammasome as a therapeutic target to improve outcomes after injury to the central nervous system (135.73)

The inflammasome constitutes one of the host's defenses against pathogens and deleterious stimuli by activating caspase-1. Inflammation with production of cytokines processed upon inflammasome activation is a crucial part of the secondary cascade of cell death induced after central nervous system (CNS) injury. The molecular mechanisms underlying trauma-induced inflammation in the CNS are poorly defined. In this study, the cellular distribution and protein association of inflammasome components were investigated in spinal cords and brains of rats subjected to moderate cervical injury and fluid-percussion brain injury, respectively. Coimmunoprecipitation experiments revealed that in the CNS, Apoptosis-Associated Speck-like protein containing a CARD (ASC) associates with caspase-1, caspase-11, NLR family, Pyrin domain containing 1 (NLRP1) and the inhibitor of apoptosis XIAP, forming the NLRP1 inflammasome. Injury to the CNS affects the composition of the inflammasome resulting in increased association of caspases-1 and -11 and NLRP1 with ASC and cleavage of XIAP. Immunohistochemistry revealed that motor neurons and cortical neurons express the NLRP1 inflammasome proteins. Therapeutic neutralization of ASC after injury inhibited inflammasome activation as shown by decreased caspase-1 activation and XIAP cleavage, resulting in reduced lesion volume and improved functional outcomes after spinal cord injury. Thus the inflammasome forms part of the innate immune response in the

CNS and its inhibition may offer a novel therapeutic strategy to improve outcomes after injury and CNS inflammatory diseases.

This research was supported by the NIH/NINDS and the US Army.

Modulation of membrane channel currents by gap junction protein mimetic peptides: size matters

Connexin mimetic peptides are widely used to assess the contribution of nonjunctional connexin channels in several processes, including ATP release. These peptides are derived from various connexin sequences and have been shown to attenuate processes downstream of the putative channel activity. Yet so far, no documentation of effects of peptides on connexin channels has been presented. We tested several connexin and pannexin mimetic peptides and observed attenuation of channel currents that is not compatible with sequence specific actions of the peptides. Connexin mimetic peptides inhibited pannexin channel currents but not the currents of the channel formed by connexins from which the sequence was derived. Pannexin mimetic peptides did inhibit pannexin channel currents but also the channels formed by connexin 46. The same pattern of effects was observed for dye transfer, except that the inhibition levels were more pronounced than for the currents. The channel inhibition by peptides shares commonalities with channel effects of polyethylene glycol (PEG), suggesting a steric block as a mechanism. PEG accessibility is in the size range expected for the pore of innexin gap junction channels, consistent with a functional relatedness of innexin and pannexin channels.

FasL, Fas, and death-inducing signaling complex (DISC) proteins are recruited to membrane rafts after spinal cord injury

The Fas/CD95 receptor-ligand system plays an essential role in apoptosis that contributes to secondary damage after spinal cord injury (SCI), but the mechanism regulating the efficiency of FasL/Fas signaling in the central nervous system (CNS) is unknown. Here, FasL/Fas signaling complexes in membrane rafts were investigated in the spinal cord of adult female Fischer rats subjected to moderate cervical SCI and sham operation controls. In sham-operated animals, a portion of FasL, but not Fas was present in membrane rafts. SCI resulted in FasL and Fas translocation into membrane raft microdomains where Fas associates with the adaptor proteins Fas-associated death domain (FADD), caspase-8, cellular FLIP long form (cFLIPL ), and caspase-3, forming a death-inducing signaling complex (DISC). Moreover, SCI induced expression of Fas in clusters around the nucleus in both neurons and astrocytes. The formation of the DISC signaling platform leads to rapid activation of initiator caspase-8 and effector caspase-3, and the modification of signaling intermediates such as FADD and cFLIP(L) . Thus, FasL/Fas-mediated signaling after SCI is similar to Fas expressing Type I cell apoptosis.

Thromboembolic stroke promotes the formation of the inflammasome complex (B70)

Inflammatory responses contribute to the pathogenesis of cerebral ischemia and stroke. Activated caspase-1 cleaves the pro-inflammatory cytokines IL-1β and IL-18, initiating a cascade of detrimental inflammatory events. Cell culture studies of macrophages have reported that activation of caspase-1 involves the formation of a macromolecular complex termed the inflammasome. Whether this complex is present after cerebral ischemia is unknown. Here, we utilized a clinically relevant model of thromboembolic stroke in mice to investigate the formation of the inflammasome and subsequent activation of inflammatory responses. Our results demonstrate for the first time that cerebral ischemia triggered the formation of a high molecular weight complex comprised of caspase-1, caspase-11, the adaptor protein ASC (apoptosis-associated speck-like protein with CARD) and NALP1 (NACHT/LRR/pyrin domain-containing protein 1) in the cerebral cortex, 24 hr after ischemia. Formation of the inflammasome complex resulted in activation of caspase-1 and cleavage of IL-1β and IL-18. Immunohistochemical analysis revealed the presence of inflammasome proteins in cortical neurons and inflammatory cells. Finally, the therapeutic potential of targeting the inflammasome after ischemia was demonstrated by reduced cytokine activation in mice treated with a neutralizing antibody against NALP1.

Therapeutic hypothermia modulates TNFR1 signaling in the traumatized brain via early transient activation of the JNK pathway and suppression of XIAP cleavage

Tumor necrosis factor (TNF) plays a critical role in pathomechanisms associated with secondary damage after traumatic brain injury (TBI). The TNF ligand-receptor system stimulates inflammation by activation of gene transcription through the IkappaB kinase (IKK)-NF-kappaB and c-Jun NH(2)-terminal kinase (JNK)-AP-1 signaling cascades. TNF signaling following TBI involves both cell survival and apoptotic pathways, but the mechanism that accounts for the dual role of TNF remains unclear. Multiple studies have reported hypothermia to be protective following TBI, but the precise mechanism has not been clearly defined. Here, TNFR1 signaling pathways were investigated in the cerebral cortex of adult male Sprague-Dawley rats subjected to moderate fluid-percussion TBI and of naïve controls. Another group was subjected to moderate TBI with 30 min of pre- and post-traumatic hypothermia (33 degrees C). Rapid and marked increases in protein expression of TNFR1 and signaling intermediates in both the IKK-NF-kappaB and JNK pathways were induced in traumatized cortices. Hypothermia decreased TNFR1 protein expression acutely in traumatized cortices and stimulated early activation of signaling intermediates in the JNK, but not the IKK-NF-kappaB, signaling pathways. Hypothermia promoted a rapid activation of caspase-3 acutely after injury but suppressed caspase-3 activation at later time points. Moreover, hypothermia treatment suppressed cleavage of X-linked inhibitor of apoptosis protein (XIAP) into fragments induced by TBI. These data suggest that hypothermia may regulate both the JNK signaling cascade via XIAP and the preconditioning pathways that activate caspases. Thus, hypothermia mediates TNFR1 responses via early activation of the JNK signaling pathway and caspase-3, leading to endogenous neuroprotective events.

Inflammatory and apoptotic signaling after spinal cord injury

Central nervous system (CNS) destruction in spinal cord injury (SCI) is caused by a complex series of cellular and molecular events. Recent studies have concentrated on signaling by receptors in the tumor necrosis factor receptor (TNFR) superfamily that mediate diverse biological outcomes ranging from inflammation to apoptosis. From the perspective of basic science research, understanding how receptor signaling mediates these divergent responses is critical in clarifying events underlying irreversible cell injury in clinically relevant models of SCI. From a clinical perspective, this work also provides novel targets for the development of therapeutic agents that have the potential to protect the spinal cord from irreversible damage and promote functional recovery. In this review, we discuss how the formation of alternate signaling complexes and receptor membrane localization after SCI can influence life and death decisions of cells stimulated through two members of the TNFR superfamily, Fas/CD95 and TNFR1.

Tumor necrosis factor receptor 1 and its signaling intermediates are recruited to lipid rafts in the traumatized brain

The tumor necrosis factor (TNF) ligand-receptor system plays an essential role in apoptosis that contributes to secondary damage after traumatic brain injury (TBI). TNF also stimulates inflammation by activation of gene transcription through the IkappaB kinase (IKK)/NF-kappaB and JNK (c-Jun N-terminal protein kinase)/AP-1 signaling cascades. The mechanism by which TNF signals between cell death and survival and the role of receptor localization in the activation of downstream signaling events are not fully understood. Here, TNF receptor 1 (TNFR1) signaling complexes in lipid rafts were investigated in the cerebral cortex of adult male Sprague Dawley rats subjected to moderate (1.8-2.2 atmospheres) fluid-percussion TBI and naive controls. In the normal rat cortex, a portion of TNFR1 was present in lipid raft microdomains, where it associated with the adaptor proteins TRADD (TNF receptor-associated death domain), TNF receptor-associated factor-2 (TRAF-2), the Ser/Thr kinase RIP (receptor-interacting protein), TRAF1, and cIAP-1 (cellular inhibitor of apoptosis protein-1), forming a survival signaling complex. Moderate TBI resulted in rapid recruitment of TNFR1, but not TNFR2 or Fas, to lipid rafts and induced alterations in the composition of signaling intermediates. TNFR1 and TRAF1 were polyubiquitinated in lipid rafts after TBI. Subsequently, the signaling complex contained activated caspase-8, thus initiating apoptosis. In addition, TBI caused a transient activation of NF-kappaB, but receptor signaling interacting proteins IKKalpha and IKKbeta were not detected in raft-containing fractions. Thus, redistribution of TNFR1 in lipid rafts and nonraft regions of the plasma membrane may regulate the diversity of signaling responses initiated by these receptors in the normal brain and after TBI.

Monoubiquitination and cellular distribution of XIAP in neurons after traumatic brain injury

XIAP is a member of the inhibitor of apoptosis (IAP) gene family that, in addition to suppressing cell death by inhibition and polyubiquitination of caspases, is involved in an increasing number of signaling cascades. Moreover, the function and regulation of XIAP in the central nervous system (CNS) is poorly understood. In this study, the authors investigated the cell-type expression, the subcellular distribution, ubiquitination of XIAP, and levels of Smac/DIABLO in the normal adult rat brain and in brains subjected to moderate traumatic brain injury (TBI). In the normal brain, XIAP was predominantly expressed in the perinuclear region of neurons. Traumatized brains showed dramatic alterations in cellular and regional expression of XIAP early after injury. Stereologic analyses of the number of XIAP-positive cells within the hippocampus of both hemispheres showed a biphasic response. Immunoprecipitation and immunoblots of extracts derived from different brain regions demonstrated that a single ubiquitin modifies XIAP. Normal cortex contained significantly higher levels of monoubiquitinated XIAP than hippocampus. TBI induced alterations in levels of monoubiquitinated XIAP that correlated with changes in XIAP distribution and immunoreactivity, suggesting that monoubiquitination of XIAP may be a regulator of XIAP location or activity. Similar levels of Smac/DIABLO were present in lysates of normal and traumatized brains. These data demonstrate for the first time a region-specific regulation of XIAP monoubiquitination in the normal adult rat brain, and after TBI, that may be a key event in the regulation of XIAP function contributing to the pathogenesis following injury.

Inhibitors of apoptosis proteins in injury and disease

The inhibitor of apoptosis (IAP) gene family prevents cell death by binding to and inhibiting caspases. In addition to negatively regulating apoptosis, IAPs bind to signaling intermediates and receptors, and participate in diverse cellular functions. Here, we describe the physiological functions of IAPs and their participation in injury and disease processes.

Therapeutic strategies targeting caspase inhibition following spinal cord injury in rats

Apoptosis-modulating therapeutics using active-site mimetic peptide ketones (z-VAD-fluoromethylketone (fmk)) have been reported to be efficacious in delaying the apoptotic response in central nervous system lesions. The purpose of the present study was to examine whether the caspase inhibitor z-VAD fmk prevents apoptosis and improves neurological deficit and tissue damage. One-hundred twenty female Sprague-Dawley rats were randomized into groups that were administered 25 microg of z-VAD-fmk or vehicle 30 min and 24 h after moderate spinal cord contusion (NYU impactor, 12.5 mm at T10). Several routes of administration were tested: (1) via Gelfoam placed on the spinal cord, (2) into the cisterna magna via a subarachnoidal catheter, (3) intravenously via the external jugular vein, or (4) intraperitoneally. Another group was injected with 50 microg of zVAD-fmk or vehicle intraperitoneally 30 min, 24, 48, and 72 h after injury. Animals were evaluated for locomotor function (BBB score) at weekly intervals for 6 weeks after injury and treatment. Spinal cords were then processed for histological analysis to determine whether zVAD-fmk treatment decreased contusion volume. Other spinal cord samples were harvested 24 h after injury and examined for cleavage of XIAP by immunoblot analysis. There were no significant differences in the BBB scores, contusion volumes, and XIAP cleavage between animals receiving the broad specific caspase inhibitor by the various routes and animals receiving vehicle alone. These findings raise critical questions about the use of peptide ketone apoptotic inhibitors in improving functional and histopathological outcomes following spinal cord injury.

Effects of finasteride on apoptosis and regulation of the human hair cycle

BACKGROUND

A number of studies have provided evidence that apoptosis is a central element in the regulation of hair follicle regression. In androgenetic alopecia (AGA), the exact location and control of key players in the apoptotic pathways remains obscure.

OBJECTIVE

In the present study, we used a panel of antibodies and investigated the spatial and cellular pattern of expression of caspases and inhibitors of apoptosis (IAPs), such as XIAP and FLIP, in men with normal scalp and in men with AGA before and after 6 months of treatment with 1 mg oral finasteride treatment.

METHODS AND RESULTS

Constitutive expression of caspases-1, -3, -8, and -9 and XIAP was detected predominantly within the isthmic and infundibular hair follicle area, basilar layer of the epidermis, and eccrine and sebaceous glands. AGA-affected tissues showed an increase in caspase (-1, -3, -6, -9) immunoreactivity with a concomitant decrease in XIAP staining. After 6 months of finasteride treatment, both caspases and XIAP were similar to levels exhibited by normal subjects. Immunoblot analysis was performed to determine antibody specificity and cellular expression of caspases. Purified populations of keratinocytes, melanocytes, dermal papilla, and dermal fibroblasts derived from human hair follicles were cultured in vitro and treated with 0.5 mm staurosporin. Time-course experiments revealed that processing of caspase-3 is a principal event during apoptosis of these hair cell types.

CONCLUSION

These data suggest that alterations in levels of caspases and IAPs regulate hair follicle homeostasis. Moreover, finasteride appears to influence caspase and XIAP expression in hair follicle cells thus signaling anagen, active growth in the hair cycle.

Regulation of caspases and XIAP in the brain after asphyxial cardiac arrest in rats

The aim of this study was to determine whether hypoxic-ischemia from asphyxial cardiac arrest activates brain caspases-1 and -3, and the anti-apoptotic protein, XIAP. Asphyxial cardiac arrest in rats was used to induce hypoxic-ischemia. A pan-caspase inhibitor (zVAD) was given in the treatment group. At 72 h after reperfusion, caspase-3 and XIAP expression were present in multiple vulnerable brain regions, whereas caspase-1 was predominantly found in the CA1 hippocampus. zVAD significantly reduced expression of caspases and XIAP and the number of ischemic neurons in the CA1 hippocampus while neurological deficit scores were improved. We conclude that hypoxic-ischemia increases caspases-1 and-3, and XIAP expression. Treatment with zVAD significantly decreases caspase and XIAP expression in these brain regions and improves neurological outcome.

Apoptotic and antiapoptotic mechanisms after traumatic brain injury

Caspase and inhibitor of apoptosis (IAP) expression was examined in rats subjected to moderate traumatic brain injury (TBI) using a parasagittal fluid-percussion brain insult (1.7 to 2.2 atm). Within 1 hour after injury, caspase-8 and -9, two initiators of apoptosis, were predominantly expressed in superficial cortical areas adjacent to the impact site and in the thalamus. Caspase-3, an effector caspase, was evident at 6 hours throughout the traumatized cerebral cortex and hippocampus. Moreover, the authors observed that XIAP, cIAP-1, and cIAP-2, members of the IAP family, were constitutively expressed in the brain. Colocalization of XIAP-immunolabled cells with cell-specific markers indicated that XIAP is expressed within neurons and a subpopulation of oligodendrocytes. Immunoblots of brain extracts revealed that the processed forms of caspase-8, -9, and -3 are present as early as 1 hour after trauma. The appearance of activated caspases corresponded with the detection of cleavage of XIAP into fragments after injury and a concomitant increase in the levels of cIAP-1 and cIAP-2 in the traumatized hemispheres. The current data are consistent with the hypotheses that caspases in both the extrinsic and intrinsic apoptotic pathways are activated after moderate TBI and that IAPs may have a protective role within the brain with alterations in levels and cleavage of IAPs that contribute to cell death in this setting.

Androgen responsive genes as they affect hair growth

Finasteride has been shown to be an effective treatment for men with androgenetic alopecia (AGA) as it restores hair growth to miniaturized hair follicles on the top of the scalp [1]. Caspases are regulators of programmed cell death, and very likely some specific caspases may function as mediators of the hair growth cycle. It is unclear whether finasteride influences the regulation of apoptosis via caspases in the hair follicle. Very little information is available regarding the role of caspases present in human hair follicles in normal scalp and in androgenetic alopecia. In this study we have analyzed the family of caspases, 1-10 along with usurpin, and XIAP, in men with normal scalp and in men with androgenetic alopecia before and after 6 months treatment with 1 mg oral finasteride treatment. Caspases 1, 3, 8 and 9 were detected predominantly within the isthmic and infundibular hair follicle area for both normal and AGA patients, however the expression of all factors, especially caspase 3 was greater in the AGA group than in the normal scalp group. AGA men had the same caspase factors but with greater expression. In the same AGA men treated with finasteride for 6 months, the expression of these factors was similar to levels in the normal group. Results from our study indicate caspase 3 to be of primary importance in normal hair homeostasis and that DHT may be signaling greater expression of caspases, inducing apoptosis in androgenetic alopecia. In conclusion, DHT may selectively regulate the caspase genes which play an important role in signaling programmed cell death, affecting the hair growth cycle.

Apoptotic and anti-apoptotic mechanisms following spinal cord injury

A number of studies have provided evidence that cell death from moderate traumatic spinal cord injury (SCI) is regulated, in part, by apoptosis that involves the caspase family of cysteine proteases. However, little or no information is available about anti-apoptotic mechanisms mediated by the inhibitors of apoptosis (IAP) family of proteins that inhibit cell death pathways. In the present study, we examined caspase and IAP expression in spinal cords of rats subjected to moderate traumatic injury. Within 6 h after injury, caspase-8 and-9 (2 initiators of apoptosis) were predominantly present in gray matter neurons within the lesion epicenter. By 3 days following spinal cord injury (SCI), caspase-8 and-9 immunoreactivity was localized to gray and white matter cells, and by 7 days following SCI, both upstream caspases were expressed in cells within white matter or within foamy macrophages in gray matter. Caspase-3, an effector caspase, was evident in a few fragmented cells in gray matter at 24 h following injury and then localized to white matter in later stages. Thus, distinct patterns of caspase expression can be found in the spinal cord following injury. XIAP, cIAP-1, and cIAP-2, members of the IAP family, were constitutively expressed in the cord. Immunoblots of spinal cord extracts revealed that the processed forms of caspases-8 and-9 and cleavage of PARP are present as early as 6 h following trauma. The expression of caspases corresponded with the detection of cleavage of XIAP into 2 fragments following injury. cIAP-1 and cIAP-2 expression remained constant during early periods following SCI but demonstrated alterations by 7 days following SCI. Our data are consistent with the idea that XIAP may have a protective role within the spinal cord, and that alteration in cleavage of XIAP may regulate cell death following SCI.

Apoptosis after traumatic human spinal cord injury

Apoptosis is a form of programmed cell death seen in a variety of developmental and disease states, including traumatic injuries. The main objective of this study was to determine whether apoptosis is observed after human spinal cord injury (SCI). The spatial and temporal expression of apoptotic cells as well as the nature of the cells involved in programmed cell death were also investigated.

The authors examined the spinal cords of 15 patients who died between 3 hours and 2 months after a traumatic SCI. Apoptotic cells were found at the edges of the lesion epicenter and in the adjacent white matter, particularly in the ascending tracts, by using histological (cresyl violet, hematoxylin and eosin) and nuclear staining (Hoechst 33342). The presence of apoptotic cells was supported by staining with the terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick-end labeling technique and confirmed by immunostaining for the processed form of caspase-3 (CPP-32), a member of the interleukin-1-beta-converting enzyme/Caenorhabditis elegans D 3 (ICE/CED-3) family of proteases that plays an essential role in programmed cell death. Apoptosis in this series of human SCIs was a prominent pathological finding in 14 of the 15 spinal cords examined when compared with five uninjured control spinal cords. To determine the type of cells undergoing apoptosis, the authors immunostained specimens with a variety of antibodies, including glial fibrillary acidic protein, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase), and CD45/68. Oligodendrocytes stained with CNPase and a number of apoptotic nuclei colocalized with positive staining for this antibody.

These results support the hypothesis that apoptosis occurs in human SCIs and is accompanied by the activation of caspase-3 of the cysteine protease family. This mechanism of cell death contributes to the secondary injury processes seen after human SCI and may have important clinical implications for the further development of protease inhibitors to prevent programmed cell death.

Apoptosis after traumatic human spinal cord injury

OBJECT

Apoptosis is a form of programmed cell death seen in a variety of developmental and disease states, including traumatic injuries. The main objective of this study was to determine whether apoptosis is observed after human spinal cord injury (SCI). The spatial and temporal expression of apoptotic cells as well as the nature of the cells involved in programmed cell death were also investigated.

METHODS

The authors examined the spinal cords of 15 patients who died between 3 hours and 2 months after a traumatic SCI. Apoptotic cells were found at the edges of the lesion epicenter and in the adjacent white matter, particularly in the ascending tracts, by using histological (cresyl violet, hematoxylin and eosin) and nuclear staining (Hoechst 33342). The presence of apoptotic cells was supported by staining with the terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick-end labeling technique and confirmed by immunostaining for the processed form of caspase-3 (CPP-32), a member of the interleukin-1beta-converting enzyme/Caenorhabditis elegans D 3 (ICE/CED-3) family of proteases that plays an essential role in programmed cell death. Apoptosis in this series of human SCIs was a prominent pathological finding in 14 of the 15 spinal cords examined when compared with five uninjured control spinal cords. To determine the type of cells undergoing apoptosis, the authors immunostained specimens with a variety of antibodies, including glial fibrillary acidic protein, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase), and CD45/68. Oligodendrocytes stained with CNPase and a number of apoptotic nuclei colocalized with positive staining for this antibody.

CONCLUSIONS

These results support the hypothesis that apoptosis occurs in human SCIs and is accompanied by the activation of caspase-3 of the cysteine protease family. This mechanism of cell death contributes to the secondary injury processes seen after human SCI and may have important clinical implications for the further development of protease inhibitors to prevent programmed cell death.

Apoptosis after traumatic human spinal cord injury

Object

Apoptosis is a form of programmed cell death seen in a variety of developmental and disease states, including traumatic injuries. The main objective of this study was to determine whether apoptosis is observed after human spinal cord injury (SCI). The spatial and temporal expression of apoptotic cells as well as the nature of the cells involved in programmed cell death were also investigated.

Methods

The authors examined the spinal cords of 15 patients who died between 3 hours and 2 months after a traumatic SCI. Apoptotic cells were found at the edges of the lesion epicenter and in the adjacent white matter, particularly in the ascending tracts, by using histological (cresyl violet, hematoxylin and eosin) and nuclear staining (Hoechst 33342). The suspected presence of apoptotic cells was supported by staining with the terminal deoxynucleotidyl transferase-mediated biotinylated-deoxyuridinetriphosphate nick-end labeling technique and confirmed by immunostaining for the processed form of caspase-3 (CPP-32), a member of the interleukin-1-beta-converting enzyme/Caenorhabditis elegans D 3 family of proteases that plays an essential role in programmed cell death. Apoptosis in this series of human SCIs was a prominent pathological finding in 14 of the 15 spinal cords examined when compared with five uninjured control spinal cords. To determine the type of cells undergoing apoptosis, the authors immunostained specimens with a variety of antibodies, including glial fibrillary acidic protein, 2,′3′-cyclic nucleotide 3′-phosphohydrolase (CNPase), and CD45/68. Oligodendrocytes stained with CNPase and a number of apoptotic nuclei colocalized with positive staining for this antibody.

Conclusions

These results support the hypothesis that apoptosis occurs in human SCIs and is accompanied by the activation of CPP-32 of the cysteine protease family. This mechanism of cell death contributes to the secondary injury processes seen after human SCI and may have important clinical implications for the further development of protease inhibitors to prevent programmed cell death.

Traumatic spinal cord injury induces nuclear factor-kappaB activation

Inflammatory responses are a major component of secondary injury and play a central role in mediating the pathogenesis of acute and chronic spinal cord injury (SCI). The nuclear factor-kappaB (NF-kappaB) family of transcription factors is required for the transcriptional activation of a variety of genes regulating inflammatory, proliferative, and cell death responses of cells. In this study we examined the temporal and cellular expression of activated NF-kappaB after traumatic SCI. We used a contusion model (N.Y.U. Impactor) to initiate the early biochemical and molecular changes that occur after traumatic injury to reproduce the pathological events associated with acute inflammation after SCI. The activation and cellular distribution of activated NF-kappaB was evaluated by using a monoclonal antibody that selectively recognizes activated p65 in a NF-kappaB dimer. Immunohistochemical and Western blot analyses demonstrated that NF-kappaB activation occurred as early as 0.5 hr postinjury and persisted for at least 72 hr. Using electrophoretic mobility shift assays (EMSA), we demonstrate that NF-kappaB is activated after SCI. In our immunohistochemical, Western, and EMSA experiments there are detectable levels of activated NF-kappaB in our control animals. Using double-staining protocols, we detected activated NF-kappaB in macrophages/microglia, endothelial cells, and neurons within the injured spinal cord. Colocalization of activated NF-kappaB with the NF-kappaB-dependent gene product, inducible nitric oxide synthase (iNOS), suggests functional implications for this transcription factor in the pathogenesis of acute spinal cord injury. Although there is considerable evidence for the involvement of an inflammatory reaction after traumatic SCI, this is the first evidence for the activation of NF-kappaB after trauma. Strategies directed at blocking the initiation of this cascade may prove beneficial as a therapeutic approach for the treatment of acute SCI.

Modulation of microglial form and immune function by factors released from goldfish optic nerves

Activation of microglia is associated with neural damage and may aid repair of the CNS. To begin to investigate their role, microglia purified from mouse brain were grown in media conditioned (CM) by goldfish optic nerve (GFON), optic tectum (GFOT), vagal lobe, telencephalon and cerebellum, and medium conditioned by rat optic nerves (RON). Microglia maintained in GFON- or GFOT-CM assumed an ameboid morphology, whereas microglia grown in media conditioned by the other neural tissues produced long, crenellated processes that resembled the ramified microglial form. Microglia maintained in all types of CM functioned as antigen presenting cells in a MHC-restricted manner when tested on conalbumin-specific Thelper (Th) cells, except for microglia maintained in GFON- and GFOT-CM. These studies suggest that GFON, in contrast to RON, produces a substance(s) that affects microglial morphology and immune reactivity, and may promote the vigorous regeneration seen in GFON after damage.

Activation of CPP32 during apoptosis of neurons and astrocytes

Members of the interleukin-1 beta-converting enzyme (ICE)/CED-3 protease family have been implicated in apoptosis in both vertebrates and invertebrates. Using primary culture methods, we report that neurons and astrocytes require the activity of the ICE/CED-3 family of proteases to undergo apoptosis induced by staurosporine, ceramide, and serum-free media. We show that specific inhibitors of ICE/CED-3 proteases can inhibit apoptosis and that cytosolic fractions from apoptosing neurons, but not healthy cells, induced apoptosis in a cell-free system. Cell extracts from neurons induced to undergo apoptosis contained ICE/ CED-3 protease activity. To determine which member of the ICE/CED-3 family was activated in neurons and astrocytes during apoptosis, we developed a novel affinity-labeling technique that labeled the active site cysteine and identified a 17-kDa subunit of the activated protease. The affinity-labeled 17-kDa protease subunit shares antigenic and molecular mass identity with the processed form of CPP32 on immunoblots, suggesting that CPP32 may be the principal effector in the apoptotic pathway in neurons and astrocytes. In time-course experiments, the activation of CPP32 preceded the detection of PARP cleavage and DNA laddering, suggesting that processing of CPP32 is a very early event in apoptosis of neurons and astrocytes and may be involved in the proteolytic action on specific cellular targets. The affinity-labeling technique developed and used in this report with neural cells allows for the sensitive detection, purification, and identification of ICE/CED-3 proteases that may be activated in other cells types under a variety of conditions, including certain diseased states.

Bcl-2 expression in neural cells blocks activation of ICE/CED-3 family proteases during apoptosis

The ICE/CED-3 family of proteases has been implicated in playing a fundamental role in programmed cell death. Bcl-2 protein represses a number of apoptotic death programs, but the biochemical mechanism of its action is not known. We investigated the activation of ICE/CED-3 proteases induced by three apoptotic stimuli (staurosporine, ceramide, and serum withdrawal) in the neuronal cell line GT1-7 and in cells overexpressing Bcl-2. Rapid activation of a 17 kDa subunit of an activated member of the ICE/CED-3 family is demonstrated by affinity-labeling GT1-7 extracts from apoptotic controls cells with a biotinylated ICE/CED-3 inhibitor. This activation corresponds to an increased ICE/CED-3-like protease activity in extracts measured by a fluorogenic substrate assay. In a cell-free system, these extracts induce apoptotic morphological changes in intact nuclei. All three activities are readily inhibited by treatment of control extracts with ICE/CED-3-like protease inhibitors. Overexpressed Bcl-2 inhibits the activation of the 17 kDa protein, the ICE/CED-3-like protease activity in the fluorogenic assay, and the induction of apoptotic morphological changes in HeLa nuclei in the cell-free system, similar to results obtained with ICE/CED-3 protease inhibitors. At the mRNA level, overexpression of Bcl-2 did not alter expression of five members of the ICE/CED-3 family: CPP32, ICE, Mch 2, Nedd 2, and TX. Overexpression of Bcl-2 prevented the apoptosis-induced processing of pro-Nedd 2 to the cleaved form. These data suggest that Bcl-2 participates upstream from the function of ICE/CED-3 proteases and may inhibit apoptosis by preventing the post-translational activation of ICE/CED-3 proteases.

Differentiation of an immortalized CNS neuronal cell line decreases their susceptibility to cytotoxic T cell lysis in vitro

RN33B cells are a temperature-sensitive neuronal cell line derived from rat E12 medullary raphe nucleus (Whittemore and White (1993) Brain Research 615, 27-40). Undifferentiated RN33B cells express class I but not class II antigens of the major histocompatibility complex (MHC), and intercellular adhesion molecule-1 (ICAM-1), a ligand for lymphocyte function associated antigen-1 (LFA-1), expressed on cytotoxic T lymphocytes (CTLs). Treatment of undifferentiated RN33B cells with interferon-gamma (IFN-gamma) upregulated both class I MHC and ICAM-1. After neuronal differentiation, expression of class I MHC antigens or ICAM-1 was undetected, even after IFN-gamma treatment. The neuronally differentiated RN33B cells were also markedly less susceptible to lysis by alloantigen-specific CTLs. These data suggest that intrinsic to the differentiation of CNS neurons is a mechanism to escape CTL-mediated cell lysis.

Cytokines and arachidonic metabolites produced during human immunodeficiency virus (HIV)-infected macrophage-astroglia interactions: implications for the neuropathogenesis of HIV disease

Human immunodeficiency virus (HIV) infection of brain macrophages and astroglial proliferation are central features of HIV-induced central nervous system (CNS) disorders. These observations suggest that glial cellular interactions participate in disease. In an experimental system to examine this process, we found that cocultures of HIV-infected monocytes and astroglia release high levels of cytokines and arachidonate metabolites leading to neuronotoxicity. HIV-1ADA-infected monocytes cocultured with human glia (astrocytoma, neuroglia, and primary human astrocytes) synthesized tumor necrosis factor (TNF-alpha) and interleukin 1 beta (IL-1 beta) as assayed by coupled reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, and biological activity. The cytokine induction was selective, cell specific, and associated with induction of arachidonic acid metabolites. TNF-beta, IL-1 alpha, IL-6, interferon alpha (IFN-alpha), and IFN-gamma were not produced. Leukotriene B4, leukotriene D4, lipoxin A4, and platelet-activating factor were detected in large amounts after high-performance liquid chromatography separation and correlated with cytokine activity. Specific inhibitors of the arachidonic cascade markedly diminished the cytokine response suggesting regulatory relationships between these factors. Cocultures of HIV-infected monocytes and neuroblastoma or endothelial cells, or HIV-infected monocyte fluids, sucrose gradient-concentrated viral particles, and paraformaldehyde-fixed or freeze-thawed HIV-infected monocytes placed onto astroglia failed to induce cytokines and neuronotoxins. This demonstrated that viable monocyte-astroglia interactions were required for the cell reactions. The addition of actinomycin D or cycloheximide to the HIV-infected monocytes before coculture reduced, > 2.5-fold, the levels of TNF-alpha. These results, taken together, suggest that the neuronotoxicity associated with HIV central nervous system disorders is mediated, in part, through cytokines and arachidonic acid metabolites, produced during cell-to-cell interactions between HIV-infected brain macrophages and astrocytes.

Resistance and susceptibility of neural cells to lysis by cytotoxic lymphocytes and by cytolytic granules

The susceptibility of neural cells to immune-mediated lysis by alloantigen-specific cytotoxic lymphocytes is important in understanding cell-mediated immune responses during rejection of transplanted neural tissues and in inflammatory responses of the central (CNS) and peripheral (PNS) nervous systems. In this study, we used 51Cr-release and granzyme A assays to examine whether primary cultures of astrocytes and CNS and PNS neurons could serve as targets for alloantigen-specific CTLs and granule-mediated lysis. The level of astrocyte killing by alloantigen-specific CTLs correlated with expression of the class I gene products of the major histocompatibility complex. Astrocytes cultured for 1-2 weeks did not express class I MHC antigens and were not susceptible to lysis by activated alloantigen-specific CTLs. Lengthening the astrocyte culture period to 3 weeks resulted in class I MHC antigen expression on the astrocyte surface and alloantigen-specific lysis. Astrocytes of all ages tested were susceptible to lysis by isolated cytolytic lymphocyte granules. PNS neurons of various ages tested also served as targets for CTLs and were lysed by isolated granules. In contrast, CNS neurons did not express class I MHC antigens and were highly resistant to killing by CTLs and lymphocyte granules. CNS neurons and astrocytes did not trigger specific granzyme A secretion from effector cells. In the presence of leucoagglutinin, CTLs-specific recognition of target cells is bypassed, and virtually any cell, regardless of its antigens, is killed nonspecifically. Although leucoagglutinin-treated CNS neurons and astrocytes triggered increased granzyme A secretion from effector cells, only astrocytes were lysed in an antigen-nonspecific manner, whereas CNS neurons remained strikingly resistant. These results suggest differences in the susceptibility of PNS and CNS neurons to T cell-mediated lysis. CNS neurons appear to possess protective mechanisms that render them refractory to CTL-mediated lysis and granule-mediated lysis, whereas PNS neurons and astrocytes are far more susceptible to both types of immune attack.

Herpes simplex virus type 1 infection of mouse astrocytes treated with basic fibroblast growth factor

We explored a possible role for the basic fibroblast growth factor (FGF) receptor during herpes simplex virus type 1 (HSV-1) infection of primary mouse astrocytes, glial cells of the central nervous system known to express FGF receptors. Plaque reduction experiments showed that treatment of astrocyte monolayers with human recombinant basic FGF failed to inhibit HSV-1 infectivity, although treatment with either heparin or poly-L-lysine reduced it by approximately 100%. Identical results were obtained when monolayers of human embryonic lung fibroblasts or African green monkey kidney cells were treated with FGF, heparin or poly-L-lysine prior to HSV-1 infection. We conclude that the basic FGF receptor is not involved in the uptake of HSV-1 during productive infection of astrocytes. Our findings suggest that this molecule is not the predominant cellular receptor for HSV-1 among vertebrate cells and plays no role in defining HSV-1 neurotropism in vivo.

Transplantation of a temperature-sensitive, nerve growth factor-secreting, neuroblastoma cell line into adult rats with fimbria-fornix lesions rescues cholinergic septal neurons

The HT4 cell line was derived from infection of a mouse neuroblastoma cell line with a retrovirus that encoded the temperature-sensitive (ts) mutant of SV40 large T antigen. At nonpermissive temperature, HT4 cells differentiated with neuronal morphology, expressed neuronal antigens, synthesized nerve growth factor (NGF) mRNA, and secreted biologically active NGF in vitro. We sought to establish whether transplanted HT4 cells expressed class I major histocompatibility complex (MHC) antigens, a partial requirement for recognition by cytotoxic T lymphocytes (CTL), and thus be susceptible to xenograft rejection. Differentiated HT4 cells expressed marginally detectable levels of class I MHC antigens, but demonstrated higher levels of class I MHC expression after treatment with interferon-gamma. However, HT4 cells were resistant to direct lysis by perforin, the pore-forming protein of CTLs, and thus may have potential use in xenograft experiments. To address whether HT4 cells secrete NGF in vivo, HT4 cells were transplanted into adults rats with unilateral fimbria-fornix transections. A ts cell line derived from P4 cerebellum, BT1, that does not differentiate with neuronal phenotype or synthesize NGF in vitro, was transplanted as a control. Six weeks posttransplant. HT4 cells had integrated into host CNS without forming tumors. In BT1 transplants, the number of medial septal acetylcholinesterase (AChE)-positive cells was reduced to 26-39% of the contralateral control side, depending on the rostrocaudal level. In HT4 transplants, the number of cholinergic septal neurons was 58-78% of the contralateral side. This percentage was significantly (P less than 0.005) greater than that seen with BT1 transplants, indicating that transplanted HT4 cells secrete NGF in vivo and rescue cholinergic septal neurons following fimbria-fornix transection.

Regulation and selective expression of Ly-6A/E, a lymphocyte activation molecule, in the central nervous system

The Ly-6 locus encodes a group of cell surface molecules found predominantly on lymphoid cells in the mouse. These proteins share several structural and functional characteristics with Thy-1, a molecule expressed in both lymphoid and neuronal tissue. Utilizing anti-Ly-6A/E monoclonal antibodies, the present results demonstrate in situ expression of these molecules in brain tissue. The findings also indicated that these molecules are not expressed during embryonic or neonatal stages of development. Moreover, although Ly-6b haplotype mice exhibited staining primary associated with vascular elements throughout the brain, Ly-6a mice exhibited staining predominantly associated with white matter limited to the hippocampal and midbrain regions. Although cultured glial and neuronal cells expressed marginally detectable levels of Ly-6A/E, the majority of GFAP+ cells in these cultures expressed high levels of Ly-6A/E following incubation with cytokines including rIFN-gamma. In addition, northern blot analysis of RNA from enriched astrocytic cultures corroborated the induction of Ly-6A/E expression. These findings have therefore established that Ly-6 is amongst those groups of genes expressed in both brain and lymphoid tissues.

Neural differentiation, NCAM-mediated adhesion, and gap junctional communication in neuroectoderm. A study in vitro

We studied the development of NCAM and gap junctional communication, and their mutual relationship in chick neuroectoderm in vitro. Expression of NCAM, as detected by monoclonal and polyclonal antibodies, and development of junctional communication, as detected by extensive cell-to-cell transfer of 400-500-D fluorescent tracers, occurred in cultures from stage-2 embryos onward. Both expressions presumably required primary induction. The differentiating cells formed discrete fields of expression on the second to third day in culture, with the NCAM fields coinciding with the junctional communication fields delineated by the tracers. Other neural differentiations developed in the following order: tetanus toxin receptors, neurofilament protein, and neurite outgrowth. Chronic treatment with antibody Fab fragments against NCAM interfered with the development of communication, suggesting that NCAM-mediated adhesion promotes formation of cell-to-cell channels. Temperature-sensitive mutant Rous sarcoma virus blocked (reversibly) communication and the subsequent development of neurofilament protein and neurites, but expression of NCAM continued.

Characterization of the altered form of the c-src gene product in neuronal cells

The pp60c-src protein that is expressed at high levels in cultures of neurons from rat embryos displays an altered mobility on SDS-polyacrylamide gels due to a structural difference in the amino-terminal region of the molecule. In this report we show that the expression of this unique form of pp60c-src, designated pp60c-src(+), is not restricted to cultured neuronal cells since the pp60c-src molecules expressed in tissues from avian and rat neural tissues also display a retarded electrophoretic mobility. The amino-terminal region from pp60c-src(+) was found to contain a novel phosphorylated tryptic peptide that contains phosphoserine. However, this phosphorylation does not appear to be responsible for the retarded electrophoretic mobility of pp60c-src(+), since the mobility of this protein is not altered by phosphatase treatment under conditions that remove greater than 95% of the radiolabeled phosphate on pp60c-src(+). The altered electrophoretic form of pp60c-src was also shown to be radiolabeled with [3H]myristate, indicating that pp60c-src is fatty-acylated in neurons, as is pp60c-src in fibroblasts. The pp60c-src molecules synthesized in vitro using rabbit reticulocyte lysates programmed with mRNA from embryonic brain migrated more slowly on SDS-polyacrylamide gels than the pp60c-src protein that was translated in vitro using RNA from embryonic limb tissue. These results suggest the possibility that the c-src mRNA expressed in neurons may undergo a unique form of processing to generate the structurally distinct form of neuronal pp60c-src(+).

Astrocytes produce interferon that enhances the expression of H-2 antigens on a subpopulation of brain cells

Using primary culture methods, we show that purified astrocytes from embryonic mouse or rat central nervous system (CNS) can be induced to produce interferon (IFN) activity when pretreated with a standard IFN-superinducing regimen of polyribonucleotide, cycloheximide, and actinomycin D, whereas IFN activity was not inducible in neuronal cultures derived from mouse CNS. Astrocyte IFN displays inductive, kinetic, physicochemical, and antigenic properties similar to those of IFN-alpha/beta, but is dissimilar to lymphocyte IFN (IFN-gamma). Treatment of pure astrocytic cultures or astrocytes cultured with neurons with astrocyte IFN or IFN-alpha/beta induced a dramatic increase in the expression of H-2 antigens on a subpopulation of astrocytes. Neither neurons nor oligodendroglia expressed detectable levels of H-2 antigens when exposed to astrocyte IFN, IFN-alpha/beta, or to IFN-beta. Injection of astrocyte IFN or IFN-alpha/beta directly into brains of newborn mice indicated that H-2 antigens were also induced in vivo. None of the IFNs (astrocyte, alpha/beta, or beta) tested induced Ia antigens on CNS cells in vitro or in vivo. Since H-2 antigens have a critical role in immune responses, astrocyte IFN may initiate and participate in immune reactions that contribute to immunoprotective and immunopathological responses in the CNS.

Differentiation and transformation of neural plate cells

The developmental potential of presumptive neural plate cells of prestreak chick embryos (stage 1) and neural plate cells from definitive streak chick embryos (stage 4) has been examined in cell culture using specific markers that identify the major cell types in the vertebrate central nervous system. The prestreak presumptive neural plate (PSPNP) cells, stage 1, assume an epithelial appearance in vitro and synthesize cellular fibronectin, but do not express markers for the neuronal, astrocytic, melanocytic, or oligodendrocytic lineages. Conversely, definitive-streak neural plate (DSNP) cells contain precursors which express cell-type-specific markers for terminally differentiated neurons, astrocytes, and melanocytes, and synthesize an extracellular matrix of cellular fibronectin. Differentiation of DSNP cells in vitro can be prevented by infection with a temperature-sensitive mutant of Rous sarcoma virus (RSV), tsNY68. Differentiation of DSNP cell transformants can be resumed by a temperature shift to the nonpermissive temperature. The morphological and biochemical changes associated with tsNY68 transformation are accompanied by alterations in pp60src kinase activity in the transformed cells.

Embryonic determination and differentiation

At the cellular level, development proceeds in a series of stages in which precursor cells are first restricted in their developmental potential (determination) and subsequently express their genetic information as specific tissues (differentiation). This paper discusses the problems encountered in seeking to understand the molecular mechanisms of thes processes and describes several model systems. A novel approach involves the inhibition of differentiation by virus transformation of the precursor cells in the chick primary mesenchyme, The transformed cells are cloned, grown to large numbers, and then analyzed biochemically.

Isolation and transformation of primary mesenchymal cells of the chick embryo

Pure primary mesenchymal cells from definitive streak stage chick embryos have been prepared free of epiblast and hypoblast cells. These cells have the potential in culture to differentiate into erythroid cells, beating heart muscle tissue, chondrocytes and epithelial cells. Transformation in vitro of pure primary mesenchymal cells by avian erythroblastosis virus (wt-AEV) and a temperature-sensitive mutant (ts34-AEV) gave rise to rapidly growing cells which remained largely undifferentiated, could be cloned in semi-solid medium and could be maintained for up to 3 months in culture. The majority of mesenchymal cells transformed by wt-AEV (MAE cells) are benzidine-negative. Gel electrophoresis of radioactively labeled cell proteins, immunoprecipitated with specific antisera against chicken hemoglobin, showed that MAE cell clones synthesize the alpha D, pi (or pi') and some unidentified "globin" polypeptide chains. Treatment of MAE cell clones with 1.0 mM n-butyrate stops cell proliferation reversibly and causes an increased synthesis of alpha D and pi (or pi') globin polypeptide chains. In certain clones of mesenchymal cells transformed by a temperature-sensitive mutant of the virus, ts34-AEV (MAE-ts34 cells), benzidine-positive cells can be induced by a shift from 37 degrees to 41 degrees C. The ability of the clone to undergo an increase in benzidine-positivity by temperature shift is decreased with the age of the clone. Different clones show a variable proportion of cells which are positive by immunofluorescence for both globin and chicken-specific histone H5. The alpha A and alpha D globin chains are synthesized in MAE-ts34 clones, but the ratios and quantities of these chains vary for different clones. Temperature shift made little difference in the types and quantities of globin chains synthesized; the increase in benzidine positivity is probably due to an increase in heme biosynthesis.