Identification of calcium-activated neutral protease as a processing enzyme of human interleukin 1 alpha

Interleukin-1alpha is a regulator of the blood-testis barrier

Throughout spermatogenesis, the Sertoli cell blood-testis barrier (BTB) is strictly regulated by cytokines, which mediate its timely restructuring, thereby allowing spermatocytes to enter the adluminal compartment of the seminiferous epithelium for development into spermatozoa. The aim herein was to investigate whether germ cells play a role in BTB restructuring via the action of interleukin-1α (IL-1α) since germ cells are known to control Sertoli cell production of this cytokine, and if yes, how these effects are mediated. When Sertoli cells were isolated from Sprague-Dawley rats and plated at high density, IL-1α (100 pg/ml) was shown to "open" the Sertoli cell barrier when its integrity was assessed by transepithelial electrical resistance measurements. Further investigation of Sertoli cells treated with IL-1α revealed striking changes in the cellular distribution of actin filaments when compared to untreated cells. These effects at the Sertoli cell barrier were mediated, in part, by epidermal growth factor receptor pathway substrate 8 (Eps8; an actin bundling and barbed-end capping protein) and actin-related protein 3 (Arp3; a component of the actin nucleation machinery). As important, an increase in the kinetics of occludin internalization but a decrease in its rate of degradation was noted following IL-1α treatment. These results indicate that IL-1α is a critical regulator of BTB dynamics.

Interleukin-1A +4845(G> T) polymorphism is a factor predisposing to acne vulgaris

Acne vulgaris is a common chronic inflammatory skin disease of multifactorial origin. The aim of this study was to clarify whether known polymorphisms of the interleukin-1A (IL1A) and IL1RN genes play a role in the pathogenesis of acne vulgaris. A positive association was found between the minor T allele of the IL1A +4845(G>T) single nucleotide polymorphism (SNP) and acne, whereas no association was found with respect to any alleles of the variable number of tandem repeats (VNTR) polymorphism of the IL1RN gene. The severity of inflammatory acne symptoms correlated with the percentage of individuals carrying the homozygote T/T genotype. These results may help to elucidate the molecular events leading to the development of acne.

The enigmatic processing and secretion of interleukin-33

Interleukin-33 (IL-33) is the most attractive novel cytokine identified as an IL-1 family member. IL-33 was first named NF-HEV (nuclear factor from high endothelial venules), as it was known to interact with nuclear chromatin although its exact intracellular functions are still to be clarified. IL-33 is now recognized as the specific ligand for the orphan IL-1 receptor family member ST2 and to be involved in polarization of T cells towards T helper 2 cell phenotype and in activation of mast cells, bosophils, eosinophils and natural killer cells. It is essential for IL-33 to be extracellularly released in order to bind to the ST2 receptor and consequently play a crucial role in inflammatory, infectious and autoimmune diseases. However, like the IL-1 family members, IL-1beta and IL-18, IL-33 mRNA is translated without a signal sequence for secretion. Additionally, IL-33 cannot be released by the processing and secretion mechanism shared by IL-1beta and IL-18 as IL-33 is not a substrate of caspase-1 and does not require proteolysis for activation. In contrast, IL-33 can be inactivated by apoptotic caspases. Accordingly, IL-33 is proposed to be released as an alarmin from necrotic cells but to be deleted during apoptosis. Besides the known autocrine, paracrine, intracrine, juxtacrine and retrocrine mechanisms of cellular interaction with cytokines, release by necrotic cells is another pathway for a cytokine to display its function, which we suggest might be called 'necrocrine'. This mini review summarizes recent progress of how IL-33 displays potential immunoregulatory roles with a particular focus on its enigmatic production.

Listeriolysin O-dependent bacterial entry into the cytoplasm is required for calpain activation and interleukin-1 alpha secretion in macrophages infected with Listeria monocytogenes

Listeriolysin O (LLO), an hly-encoded cytolysin of Listeria monocytogenes, plays an essential role in the entry of L. monocytogenes into the host cell cytoplasm. L. monocytogenes-infected macrophages produce various proinflammatory cytokines, including interleukin-1 alpha (IL-1 alpha), that contribute to the host immune response. In this study, we have examined IL-1 alpha production in macrophages infected with wild-type L. monocytogenes or a nonescaping mutant strain deficient for LLO (Delta hly). Expression of IL-1 alpha mRNA and accumulation of pro-IL-1 alpha in the cytoplasm were induced by both strains. In contrast, the secretion of the mature form of IL-1 alpha from infected macrophages was observed in infection with wild-type L. monocytogenes but not with the Delta hly mutant. A recovery of the ability to induce IL-1 alpha secretion was shown in a mutant strain complemented with the hly gene. The Toll-like receptor (TLR)/MyD88 signaling pathway was exclusively required for the expression of pro-IL-1 alpha, independently of LLO-mediated cytoplasmic entry of L. monocytogenes. The LLO-dependent secretion of mature IL-1 alpha was abolished by addition of calcium chelators, and only LLO-producing L. monocytogenes strains were able to induce elevation of the intracellular calcium level in infected macrophages. A calcium-dependent protease, calpain, was implicated in the maturation and secretion of IL-1 alpha induced by LLO-producing L. monocytogenes strains based on the effect of calpain inhibitor. Functional activation of calpain was detected in macrophages infected with LLO-producing L. monocytogenes strains but not with a mutant strain lacking LLO. These results clearly indicated that LLO-mediated cytoplasmic entry of bacteria could induce the activation of intracellular calcium signaling, which is essential for maturation and secretion of IL-1 alpha in macrophages during L. monocytogenes infection through activation of a calcium-dependent calpain protease. In addition, recombinant LLO, when added to macrophages infected with the Delta hly strain, could induce calcium influx and IL-1 alpha secretion at doses exhibiting cytolytic activity, suggesting that LLO produced by intracellular L. monocytogenes may be implicated in induction of calcium influx through pore formation.

Dual functionality of interleukin-1 family cytokines: implications for anti-interleukin-1 therapy

Dysregulated inflammation contributes to disease pathogenesis in both the periphery and the brain. Cytokines are coordinators of inflammation and were originally defined as secreted mediators, released from expressing cells to activate plasma membrane receptors on responsive cells. However, a group of cytokines is now recognized as having dual functionality. In addition to their extracellular effects, these cytokines act inside the nuclei of cytokine-expressing or cytokine-responsive cells. Interleukin-1 (IL-1) family cytokines are key pro-inflammatory mediators, and blockade of the IL-1 system in inflammatory diseases is an attractive therapeutic goal. All current therapies target IL-1 extracellular actions. Here we review evidence that suggests IL-1 family members have dual functionality. Several IL-1 family members have been detected inside the nuclei of IL-1-expressing or IL-1-responsive cells, and intranuclear IL-1 is reported to regulate gene transcription and mRNA splicing. However, further work is required to determine the impact of IL-1 intranuclear actions on disease pathogenesis. The intranuclear actions of IL-1 family members represent a new and potentially important area of IL-1 biology and may have implications for the future development of anti-IL-1 therapies.

Reactive oxygen species in HaCaT keratinocytes after UVB irradiation are triggered by intracellular Ca(2+) levels

It is recognized that reactive oxygen species (ROS) are responsible for skin damage due to UVB-radiation (UVB-R). However, the triggering substance(s) for ROS generation after UVB-R is uncertain with respect to the activation of NADPH oxidase (Nox), xanthine oxidase (XOD), and respiratory chain-chain reactions in mitochondria. As a first step in identifying the trigger(s) for UVB-induced ROS generation, we examined the relationship between Ca(2+) levels and ROS generation in HaCaT keratinocytes. UVB-R exposure of HaCaT keratinocytes resulted in an immediate elevation of ROS that recurred 7 hours later. This was accompanied by immediately elevated intracellular Ca(2+) . A Ca(2+) chelating agent, BAPTA, abolished the elevation of ROS after UVB-R completely. In addition, exogenous H(2)O(2) did not increase intracellular Ca(2+) levels. This suggests that intracellular Ca(2+) is the first trigger for UVB-induced ROS generation.Journal of Investigative Dermatology Symposium Proceedings (2009) 14, 50-52; doi:10.1038/jidsymp.2009.12.

Mature interleukin-33 is produced by calpain-mediated cleavage in vivo

Interleukin (IL)-33 is a novel member of the IL-1 family. IL-33 is primarily synthesized as a 30-kDa precursor (pro-IL-33). Pro-IL-33 is cleaved by caspase-1 into an 18-kDa mature form (mature IL-33) in vitro. Recombinant mature IL-33 has been known to induce T-helper type-2 (Th2)-associated cytokines and inflammatory cytokines via its receptor, ST2L. However, processing of pro-IL-33 in vivo has not been clarified yet. Here, we report that calpain mediates pro-IL-33 processing in vivo. Pro-IL-33 was expressed by stimulating human epithelial cells with phorbol 12-myristate 13-acetate. Calcium ionophore induced pro-IL-33 cleavage and mature IL-33 production. This cleavage was inhibited by treatment with a calcium chelator and calpain inhibitors. Moreover, short interfering RNA-mediated knockdown of calpains suppressed pro-IL-33 cleavage. These results indicate that calpains play a critical role in pro-IL-33 processing in vivo.

Virus binding to a plasma membrane receptor triggers interleukin-1 alpha-mediated proinflammatory macrophage response in vivo

The recognition of viral components by host pattern-recognition receptors triggers the induction of the antiviral innate immune response. Toll-like receptor 9 (TLR9) and NLRP3 inflammasome were shown to be the principal specific sensors of viral double-stranded DNA. Here we present evidence that macrophages in vivo activated an innate immune response to a double-stranded DNA virus, adenovirus (Ad), independently of TLR9 or NLRP3 inflammasome. In response to Ad, macrophage-derived IL-1 alpha triggered IL-1RI-dependent production of a defined set of proinflammatory cytokines and chemokines. The IL-1 alpha-mediated response required a selective interaction of virus arginine-glycine-aspartic acid (RGD) motifs with macrophage beta(3) integrins. Thus, these data identify IL-1 alpha-IL-1RI as a key pathway allowing for the activation of proinflammatory responses to the virus, independently of its genomic nucleic acid recognition.

Metabolic basis of benzene toxicity

Potential metabolic mechanisms underlying the haemopoietic toxicity of benzene include bioactivation of phenolic metabolites of benzene by peroxidases in bone marrow and ring opening reactions to generate muconate derivatives. Peroxidase-mediated activation of phenolic metabolites of benzene generates reactive quinones which can be detoxified by NAD(P)H:quinone acceptor oxidoreductase (NQO1). The major peroxidase enzyme in bone marrow is myeloperoxidase (MPO) and potential target cells for phenolic metabolites of benzene were characterized in bone marrow stroma on the basis of high MPO:NQO1 ratios. MPO was found to be expressed at the level of myeloid progenitor cells in both murine (lineage negative cells) and human (CD34+ cells) systems. This suggests that progenitor cells may be relevant targets of phenolic metabolites of benzene resulting in aberrant haemopoiesis. A polymorphism in NQO1 is also described which leads to a complete lack of NQO1 activity. The toxicological significance of this polymorphism with respect to benzene toxicity is under investigation.

Interleukin-33 - cytokine of dual function or novel alarmin?

Cytokines are thought to exert biological effects through their specific cell surface membrane receptors but increasing evidence suggests that some also function within the nucleus. Here, we review current knowledge of such cytokines, including the novel interleukin (IL)-1 family member IL-33. Its extracellular function has attracted much recent attention as a ligand for the Th2-associated ST2 receptor, but the discoveries of its nuclear functions and modes of secretion are only just beginning to surface. We review the currently available data on IL-33 regulation, nuclear function and release and discuss them in the context of other intranuclear cytokines and the prototype alarmin HMGB1, considering to what extent IL-33 can be seen as a novel member of the alarmin family.

Caspases as therapeutic targets

The development of small molecules to modulate caspase activity offers a novel therapeutic strategy in the treatment of apoptosis-related and inflammatory diseases. Caspases are key mediators of apoptosis and inflammation; deregulation of their activation or expression can lead to the development of conditions such as neurodegenerative and autoinflammatory disorders. This review details the different caspase-associated disorders while focusing on caspase-1 inhibition as a potential therapeutic strategy. Problems facing the development of effective and safe caspase therapeutics will also be addressed.

Complex effects of IL1A polymorphism and calpain inhibitors on interleukin 1 alpha (IL-1 alpha) mRNA levels and secretion of IL-1 alpha protein

Alleles of IL1A-889(C>T) and IL1A+4845(G>T) are in linkage disequilibrium. Interleukin 1alpha (IL-1alpha) is produced as a precursor protein and cleaved at positions 117-118 by calpain, generating a mature protein for export. IL1A+4845 affects amino acids expressed at position 114 and hence may modulate calpain-mediated cleavage. We sought evidence for this mechanism in intact cells. Blood leukocytes from heterozygous donors released more IL-1alpha protein than cells from IL1A(1,1) donors, while release from IL1A(2,2) cells was variable. Genotype did not affect levels of IL-1alpha mRNA, so differential cleavage of the precursor is a feasible mechanism. However, genotype also had no effect on inhibition of IL-1alpha release by pretreatment with calpain inhibitors, and calpain inhibitors reduced IL-1alpha and tumor necrosis factor alpha mRNA levels. Hence, calpain inhibitors probably affect inhibition of signal transduction pathway rather than cleavage of IL-1alpha protein. As ratios of mu-calpain/calpastatin were lowest in heterozygous donors, genetically determined IL-1alpha levels may modulate transcription of calpain and calpastatin. This could reduce the impact of IL1A genotype on IL-1alpha secretion and amplify individual variation in levels generated in culture.

Early cytokine expression in mouse sciatic nerve after chronic constriction nerve injury depends on calpain

Nerve injury initiates Wallerian degeneration with subsequent alterations of cytokine expression contributing to neuropathic pain. To investigate the very early temporal pattern of cytokine regulation we studied 140 mice of C57Bl/6J background after chronic constriction injury (CCI) of the right sciatic nerve and measured the relative mRNA expression of the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF) and interleukin-1beta (IL-1beta) and of the anti-inflammatory cytokines IL-4 and IL-10 with quantitative real-time polymerase chain reaction (qRT-PCR). The measurements were performed in ipsi- and contralateral sciatic nerves and dorsal root ganglia (DRG) 1, 3, 6, 9, 12, 24 h, and 3 and 7 days after CCI. We found an ipsilateral upregulation of TNF, IL-1beta and IL-10 mRNA levels as early as one hour after CCI. To investigate upstream regulatory mechanisms, we used inhibitors to the N-methyl-d-aspartate (NMDA) receptor ((+)-MK-801) and to calpain (MDL-28170). MDL-28170, but not (+)-MK-801 inhibited TNF and IL-1beta upregulation one hour after CCI. This leads us to suggest that calpain is one of the earliest mediators of cytokine upregulation in injured peripheral nerves.

Comparison of the human and canine cytokines IL-1(alpha/beta) and TNF-alpha to orthologous other mammalians

The cytokines interleukin-1 (IL-1alpha and IL-1beta) and the tumor necrosis factor-alpha (TNF-alpha) both play a major role in the initiation and regulation of inflammation and immunity responses. Polymorphisms within the gene sequences of these cytokines IL-1 and TNF-alpha have been proposed to play an important role in the pathogenesis of certain diseases. Affecting nearly every organ, various diseases, including some cancers, are described to be associated with an increased level of IL-1 and TNF-alpha proteins, for example, solid tumors, hematologic malignancies, malignant histiocytosis, autoimmune disorders, Alzheimer's disease, Parkinson's disease, sepsis, and rheumatoid arthritis. Regarding genetic backgrounds and pathways, numerous canine diseases show close similarities to their human counterparts. As a genetic model, the dog could be used to unravel the genetic mechanisms, for example, in particular the predispositions, the development, and progression of cancer and metabolic diseases. The identity comparison of gene and protein sequences of different species could be used to elucidate the structure and function of the genes and proteins by identifying the evolutionary conserved regions and domains. Herein we analyzed in detail the mRNA and protein structures and identities of the present known mammalian (human, canine, murine, rat, ovine, equine, feline, porcine, and bovine) TNF-alpha, IL-1alpha, and IL-1beta mRNAs and proteins. Additionally, based on the canine genome sequence, we derived in silico the complete mRNA structures of the IL-1alpha and IL-1beta mRNAs.

Contribution of single nucleotide polymorphisms of the IL1A gene to the cleavage of precursor IL-1alpha and its transcription activity

We previously demonstrated the association of IL1A gene single nucleotide polymorphisms (SNPs) with susceptibility to systemic sclerosis (SSc) patients. In this study, we explored the effects of SNP on the transcriptional activity and processing of the precursor IL-1alpha (pre-IL-1alpha) in skin fibroblasts. Two kinds of promoter regions of the IL1A gene were prepared including C or T at -889, referred to C/IL1A and T/IL1A, and inserted into a luciferase reporter vector (pGL3). Skin fibroblasts were explanted from two SSc patients whose genomic DNA contained GG and TT genotypes at +4845 of the IL1A gene, respectively. Cell lysates were collected and reacted with various concentrations of calpain, and then the processing of pre-IL-1alpha was analyzed by Western blotting using monoclonal anti-IL-1alpha antibody. A SNP was determined by the allelic discrimination method using fluorescence-labeled Taq-Man probes. Significant differences in the luciferase activities were not detected between pGL3 (C/IL1A) and pGL3 (T/IL1A) in SSc fibroblasts. Calpain required a 100-fold higher concentration to process the pre-IL-1alpha containing Ala at the 114th amino acid than that to do containing Ser. The frequency of the GG genotype was significantly higher in SSc patients than that in healthy donors, whereas the frequency of TT genotype was significantly higher in RA patients than that in healthy donors. Our observation showed that the SNP at +4845 affected the enzymatic efficiency of the protease in cleaving pre-IL-1alpha. Pre-IL-1alpha with Ala, which was high in frequency in SSc patients, was more resistant to be cleaved by proteases in human sera than pro-IL-1alpha with Ser.

Hypoxia-induced cell death of HepG2 cells involves a necrotic cell death mediated by calpain

To elucidate mechanism of cell death in response to hypoxia, we attempted to compare hypoxia-induced cell death of HepG2 cells with cisplatin-induced cell death, which has been well characterized as a typical apoptosis. Cell death induced by hypoxia turned out to be different from cisplatin-mediated apoptosis in cell viability and cleavage patterns of caspases. Hypoxia-induced cell death was not associated with the activation of p53 while cisplatin-induced apoptosis is p53 dependent. In order to explain these differences, we tested involvement of micro-calpain and m-calpain in hypoxia-induced cell death. Calpains, especially micro-calpain, were initially cleaved by hypoxia, but not by cisplatin. Interestingly, the treatment of a calpain inhibitor restored PARP cleavage that was absent during hypoxia, indicating the recovery of activated caspase-3. The inhibition of calpains prevented proteolysis induced by hypoxia. In addition, hypoxia resulted in a necrosis-like morphology while cisplatin induced an apoptotic morphology. The calpain inhibitor prevented necrotic morphology induced by hypoxia and converted partially to apoptotic morphology with nuclear segmentation. Our result suggests that calpains are involved in hypoxia-induced cell death that is likely to be necrotic in nature and the inhibition of calpain switches hypoxia-induced cell death to apoptotic cell death without affecting cell viability.

Intracellular IL-1alpha-binding proteins contribute to biological functions of endogenous IL-1alpha in systemic sclerosis fibroblasts

The aberrant production of precursor IL-1alpha (pre-IL-1alpha) in skin fibroblasts that are derived from systemic sclerosis (SSc) is associated with the induction of IL-6 and procollagen, which contributes to the fibrosis of SSc. However, little is understood about how intracellular pre-IL-1alpha regulates the expression of the other molecules in fibroblasts. We report here that pre-IL-1alpha can form a complex with IL-1alpha-binding proteins that is translocated into the nuclei of fibroblasts. Immunoprecipitation that used anti-human IL-1alpha Ab and (35)S-labeled nuclear extracts of fibroblasts showed three specific bands (approximately equal to 31, 35, and 65 kDa). The 31-kDa molecule was identified as pre-IL-1alpha, and the 35- and 65-kDa molecules might be pre-IL-1alpha-binding proteins. A partial sequencing for the 10 aa from the N-terminals of the molecules showed 100% homology for HAX-1 (HS1-associated protein X-1) and IL-1 receptor type II (IL-1RII). Suppression of the genes of HAX-1 or IL-1RII induced the inhibitory effects of IL-1 signal transduction, including production of IL-6 and procollagen, by fibroblasts. In particular, pre-IL-1alpha was not translocated into the nucleus by an inhibition of HAX-1. These findings reveal that nuclear localization of pre-IL-1alpha depends on the binding to HAX-1 and that biological activities might be elicited by the binding to both HAX-1 and IL-1RII in SSc fibroblasts.

Regulation of IL-1 family cytokines IL-1alpha, IL-1 receptor antagonist, and IL-18 by 1,25-dihydroxyvitamin D3 in primary keratinocytes

IL-1 family cytokines are key mediators of inflammatory response. Excessive production of these cytokines by keratinocytes has been implicated in inflammatory and hyperproliferative skin diseases. Given the immunosuppressive role of 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) and its clinical application in treatment of psoriasis, we investigated the effect of 1,25(OH)(2)D(3) on the expression of IL-1alpha, intracellular IL-1 receptor antagonist (icIL-1Ra), and IL-18 in mouse primary keratinocytes. Treatment of keratinocytes with 1,25(OH)(2)D(3) increased the expression of IL-1alpha and icIL-1Ra and decreased the expression of IL-18 in dose- and time-dependent manners. The magnitude of icIL-1Ra induction was much greater than that of IL-1alpha so that the ratio of icIL-1Ra to IL-1alpha was markedly increased, leading to repression of IL-1 activity. The regulation of these three cytokines by 1,25(OH)(2)D(3) was mediated by vitamin D receptor (VDR), as 1,25(OH)(2)D(3) had no effect in VDR(-/-) keratinocytes, whereas the effect was restored in cells derived from VDR(-/-) mice expressing human VDR. 1,25(OH)(2)D(3) appeared to use different mechanisms to regulate the biosynthesis of IL-1alpha and icIL-1Ra: it increased IL-1alpha mRNA stability whereas it enhanced icIL-1Ra gene transcription. The basal IL-18 expression and activity were much higher in VDR(-/-) keratinocytes and skin, underscoring the importance of the repressive role of vitamin D in IL-18 production. Similar regulation of these cytokines was also seen in primary human keratinocytes. Collectively, these results suggest that vitamin D modulates cutaneous inflammatory reactions, at least in part, by increasing the IL-1Ra to IL-1alpha ratio and suppressing IL-18 synthesis in keratinocytes.

A comprehensive map of the toll-like receptor signaling network

Recognition of pathogen-associated molecular signatures is critically important in proper activation of the immune system. The toll-like receptor (TLR) signaling network is responsible for innate immune response. In mammalians, there are 11 TLRs that recognize a variety of ligands from pathogens to trigger immunological responses. In this paper, we present a comprehensive map of TLRs and interleukin 1 receptor signaling networks based on papers published so far. The map illustrates the possible existence of a main network subsystem that has a bow-tie structure in which myeloid differentiation primary response gene 88 (MyD88) is a nonredundant core element, two collateral subsystems with small GTPase and phosphatidylinositol signaling, and MyD88-independent pathway. There is extensive crosstalk between the main bow-tie network and subsystems, as well as feedback and feedforward controls. One obvious feature of this network is the fragility against removal of the nonredundant core element, which is MyD88, and involvement of collateral subsystems for generating different reactions and gene expressions for different stimuli.

The Response of Human Epithelial Cells to TNF Involves an Inducible Autocrine Cascade

Tumor necrosis factor (TNF) is a proinflammatory cytokine that induces conflicting pro- and antiapoptotic signals whose relative strengths determine the extent of cell death. TNF receptor (TNFR) has been studied in considerable detail, but it is not known how crosstalk among antagonistic pro- and antiapoptotic signals is achieved. Here we report an experimental and computational analysis of crosstalk between prodeath TNF and prosurvival growth factors in human epithelial cells. By applying classifier-based regression to a cytokine-signaling compendium of approximately 8000 intracellular protein measurements, we demonstrate that cells respond to TNF both directly, via activated TNF receptor, and indirectly, via the sequential release of transforming growth factor-alpha (TGF-alpha), interleukin-1alpha (IL-1alpha), and IL-1 receptor antagonist (IL-1ra). We refer to the contingent and time-varying series of extracellular signals induced by TNF as an "autocrine cascade." Time-dependent crosstalk of synergistic and antagonistic autocrine circuits may serve to link cellular responses to the local environment.

Presence of a cytoplasmic retention sequence within the human interleukin-1alpha precursor

Interleukin (IL)-1alpha is primarily translated as a 33 kDa molecule (IL-1alpha1-271), and then processed into a 17 kDa molecule (IL-1alpha119-271) by calpain. The precursor region of IL-1alpha (IL-1 alpha1-118) contains a nuclear localization signal (KVLKKRRL, residues 79-86). We investigated the intracellular localization of IL-1alpha fused with green fluorescent protein or beta-galactosidase. IL-1alpha1-118 was localized exclusively in the nucleus, but IL-1 alpha1-271 in both the nucleus and the cytoplasm, suggesting the presence of a cytoplasmic retention signal within the mature region of IL-1alpha. Furthermore, the intracellular localization of IL-1alpha with deletions from the C terminus, internal deletions and point mutations suggested that the cytoplasmic retention signal is located within residues 168-201.

Autoantibodies directed against the protease inhibitor calpastatin in psoriasis

Psoriasis is believed to be a T cell-mediated autoimmune disease, but also exhibits autoantibody production. Calpastatin is an endogenous inhibitor of calpain, a ubiquitous protease that regulates inflammatory processes. Anti-calpastatin autoantibody was first identified as an autoantibody specific to rheumatoid arthritis, but has been also detected in other autoimmune diseases. In this study, we examined the presence and levels of anti-calpastatin antibody in 77 psoriasis patients by enzyme-linked immunosorbent assay. Compared with normal controls, psoriasis patients exhibited significantly elevated IgG anti-calpastatin antibody levels that were similar to those found in rheumatoid arthritis patients. Remarkably, IgG anti-calpastatin autoantibody in sera from psoriasis patients inhibited calpastatin activity. Calpain II expression was up-regulated in psoriasis skin lesions compared with normal skin while calpastatin expression was normal. The results of this study reveal the presence of anti-calpastatin autoantibody in psoriasis.

Therapeutic potential of targeting IL-1 and IL-18 in inflammation

Interleukin (IL)-1 and IL-18 are cytokines that play a major role in autoimmune and inflammatory human disease. Both cytokines drive a wide range of pro-inflammatory effector networks in many cell types and use common signal transduction cascades. IL-1, IL-18 and other members of the IL-1 superfamily are expressed at elevated levels in tissue and fluid samples isolated from patients with many chronic inflammatory diseases. These cytokines are primary drivers in acute and chronic animal models of inflammation and their blockade has been shown to ameliorate disease in preclinical studies. Biological agents that target IL-1 have demonstrated efficacy in patients with rheumatoid arthritis, and further agents targeting IL-1 or IL-18 neutralisation are in clinical development. The potential for such agents spans human disease where tissue destruction is a primary end point of cytokine action.

Vasohibin as an endothelium-derived negative feedback regulator of angiogenesis

Negative feedback is a crucial physiological regulatory mechanism, but no such regulator of angiogenesis has been established. Here we report a novel angiogenesis inhibitor that is induced in endothelial cells (ECs) by angiogenic factors and inhibits angiogenesis in an autocrine manner. We have performed cDNA microarray analysis to survey VEGF-inducible genes in human ECs. We characterized one such gene, KIAA1036, whose function had been uncharacterized. The recombinant protein inhibited migration, proliferation, and network formation by ECs as well as angiogenesis in vivo. This inhibitory effect was selective to ECs, as the protein did not affect the migration of smooth muscle cells or fibroblasts. Specific elimination of the expression of KIAA1036 in ECs restored their responsiveness to a higher concentration of VEGF. The expression of KIAA1036 was selective to ECs, and hypoxia or TNF-alpha abrogated its inducible expression. As this molecule is preferentially expressed in ECs, we designated it "vasohibin." Transfection of Lewis lung carcinoma cells with the vasohibin gene did not affect the proliferation of cancer cells in vitro, but did inhibit tumor growth and tumor angiogenesis in vivo. We propose vasohibin to be an endothelium-derived negative feedback regulator of angiogenesis.

Varicella-zoster virus transfer to skin by T Cells and modulation of viral replication by epidermal cell interferon-alpha

Primary infection with varicella-zoster virus (VZV) causes the characteristic syndrome of varicella, or chickenpox. Experiments in severe combined immunodeficiency mice with human skin grafts (SCIDhu mice) indicate that VZV infection of T cells can mediate transfer of infectious virus to skin. VZV-infected T cells reached epithelial sites of replication within 24 h after entering the circulation. Memory CD4⁺ T cells were the predominant population recovered from skin in SCIDhu mice given uninfected or infected mononuclear cells, suggesting that immune surveillance by memory T cells may facilitate VZV transfer. The increased susceptibility of memory T cells to VZV infection may further enhance their role in VZV pathogenesis. During VZV skin infection, viral gene products down-regulated interferon-α to permit focal replication, whereas adjacent epidermal cells mounted a potent interferon-α response against cell–cell spread. Interleukin-1α, although activated in VZV-infected cells, did not trigger expression of endothelial adhesion molecules, thereby avoiding early recruitment of inflammatory cells. The prolonged varicella incubation period appears to represent the time required for VZV to overcome antiviral responses of epidermal cells and generate vesicles at the skin surface. Modulation of VZV replication by cutaneous innate immunity may avoid an incapacitating infection of the host that would limit opportunities for VZV transmission.

Disruption of hydrophobic stability of biomembranes is the earliest event in several clinical disorders

Hydrophobic attractive force is the major force in maintaining the stability of biomembranes, yielding coordinated functionality to the embedded proteins that they contain. This force between the composite linear hydrocarbons of the biomembranes is a function of their length and their mutual parallel distance from each other, and is extremely sensitive to this distance. Extracellular, natural linear hydrocarbons of certain length and shape can intercalate into lipid matrix of the biomembranes, reducing their innate hydrophobic net strength in a concentration-dependent manner, making them loose, leaky, and thus gaining the credence of stimulus-generating agents. In physiological circulatory concentration, these molecules may have a role for the maintenance of cellular homeostasis. However, in stagnating physiological excess, these same agents can become acutely or chronically stimulating and, therefore, disease-precipitating. Such situations do exist in the clinical disorders of acne, atherosclerosis, acute pancreatitis, diabetes, diabetic retinopathy, homocysteinemea, and stress. A systematic approach, beginning with surface film studies with the suspect linear hydrocarbons, can be followed up with in vitro and in vivo studies. This should substantiate or negate the view presented here. Isolated information, along these lines, already exist in literature. The example of acne is a suitable starting point to elaborate this view, for sebaceous gland of the human pilosebaceous unit (PSU) contains all the exemplary, stimulus-inducing linear hydrocarbons to generate surface-reaction on the pilosebaceous ductal surface.

Inflammatory Caspases

Caspases not only play an essential role during apoptotic cell death, but a subfamily of them-the inflammatory caspases-are associated with immune responses to microbial pathogens. Activation of inflammatory caspases, such as caspase-1 and caspase-5, occurs upon assembly of an intracellular complex, designated the inflammasome. This results in the cleavage and activation of the proinflammatory cytokines IL-1beta and IL-18. Mutations in one of the scaffold proteins of the inflammasome, NALP3/Cryopyrin, are associated with autoinflammatory disorders underscoring the importance of regulating inflammatory caspase activation.

Membrane-associated IL-1 contributes to chronic synovitis and cartilage destruction in human IL-1 alpha transgenic mice

IL-1 molecules are encoded by two distinct genes, IL-1alpha and IL-1beta. Both isoforms possess essentially identical activities and potencies, whereas IL-1alpha, in contrast to IL-1beta, is known to act as a membrane-associated IL-1 (MA-IL-1) and plays an important role in a variety of inflammatory situations. The transgenic (Tg) mouse line (Tg1706), which was generated in our laboratory, overexpresses human IL-1alpha (hIL-1alpha) and exhibits a severe arthritic phenotype characterized by autonomous synovial proliferation with subsequent cartilage destruction. Because the transgene encoded Lys(64) to Ala(271) of the hIL-1alpha amino acid sequence, Tg mice may overproduce MA-IL-1 as well as soluble IL-1alpha. The present study investigated whether MA-IL-1 contributes to synovial proliferation and cartilage destruction in the development of arthritis. Flow cytometric analysis revealed that both macrophage-like and fibroblast-like synoviocytes constitutively produce MA-IL-1. D10 cell proliferation assay revealed MA-IL-1 bioactivity of paraformaldehyde-fixed synoviocytes and the further induction of endogenous mouse MA-IL-1 via autocrine mechanisms. MA-IL-1 expressed on synoviocytes triggered synoviocyte self-proliferation through cell-to-cell (i.e., juxtacrine) interactions and also promoted proteoglycan release from the cartilage matrix in chondrocyte monolayer culture. Interestingly, the severity of arthritis was significantly correlated with MA-IL-1 activity rather than with soluble IL-1alpha activity or concentration of serum hIL-1alpha. Moreover, when the Tg1706 line was compared with the Tg101 line, which selectively overexpresses the 17-kDa mature hIL-1alpha, the severity of arthritis was significantly higher in the Tg1706 line than in the Tg101 line. These results suggest that MA-IL-1 contributes to synoviocyte self-proliferation and subsequent cartilage destruction in inflammatory joint disease such as rheumatoid arthritis.

On the sequential determinants of calpain cleavage

The structural clues of substrate recognition by calpain are incompletely understood. In this study, 106 cleavage sites in substrate proteins compiled from the literature have been analyzed to dissect the signal for calpain cleavage and also to enable the design of an ideal calpain substrate and interfere with calpain action via site-directed mutagenesis. In general, our data underline the importance of the primary structure of the substrate around the scissile bond in the recognition process. Significant amino acid preferences were found to extend over 11 residues around the scissile bond, from P(4) to P(7)'. In compliance with earlier data, preferred residues in the P(2) position are Leu, Thr, and Val, and in P(1) Lys, Tyr, and Arg. In position P(1) ', small hydrophilic residues, Ser and to a lesser extent Thr and Ala, occur most often. Pro dominates the region flanking the P(2)-P(1)' segment, i.e. positions P(3) and P(2)'-P(4)'; most notable is its occurrence 5.59 times above chance in P(3)'. Intriguingly, the segment C-terminal to the cleavage site resembles the consensus inhibitory region of calpastatin, the specific inhibitor of the enzyme. Further, the position of the scissile bond correlates with certain sequential attributes, such as secondary structure and PEST score, which, along with the amino acid preferences, suggests that calpain cleaves within rather disordered segments of proteins. The amino acid preferences were confirmed by site-directed mutagenesis of the autolysis sites of Drosophila calpain B; when amino acids at key positions were changed to less preferred ones, autolytic cleavage shifted to other, adjacent sites. Based on these preferences, a new fluorogenic calpain substrate, DABCYLTPLKSPPPSPR-EDANS, was designed and synthesized. In the case of micro- and m-calpain, this substrate is kinetically superior to commercially available ones, and it can be used for the in vivo assessment of the activity of these ubiquitous mammalian calpains.

The precursor form of IL-1alpha is an intracrine proinflammatory activator of transcription

Although most cytokines are studied for biological effects after engagement of their specific cell surface membrane receptors, increasing evidence suggests that some function in the nucleus. In the present study, the precursor form of IL-1alpha was overexpressed in various cells and assessed for activity in the presence of saturating concentrations of IL-1 receptor antagonist to prevent receptor signaling. Initially diffusely present in the cytoplasm of resting cells, IL-1alpha translocated to the to nucleus after activation by endotoxin, a Toll-like receptor ligand. The IL-1alpha precursor, but not the C-terminal mature form, activated the transcriptional machinery in the GAL4 system by 90-fold; a 50-fold increase was observed using only the IL-1alpha propiece, suggesting that transcriptional activation was localized to the N terminus where the nuclear localization sequence resides. Under conditions of IL-1 receptor blockade, intracellular overexpression of the precursor and propiece forms of IL-1alpha were sufficient to activate NF-kappaB and AP-1. Stable transfectants overproducing precursor IL-1alpha released the cytokines IL-8 and IL-6 but also exhibited a significantly lower threshold of activation to subpicomolar concentrations of tumor necrosis factor alpha or IFN-gamma. Thus, intracellular functions of IL-1alpha might play an unforeseen role in the genesis of inflammation. During disease-driven events, the cytosolic precursor moves to the nucleus, where it augments transcription of proinflammatory genes. Because this mechanism of action is not affected by extracellular inhibitors, reducing intracellular functions of IL-1alpha might prove beneficial in some inflammatory conditions.

Inhibition of calpains, by treatment with leupeptin, improves motoneuron survival and muscle function in models of motoneuron degeneration

The effect of treatment with leupeptin, a calpain inhibitor, on motoneuron survival and muscle function was examined in in vitro and in vivo models of motoneuron degeneration. Exposure of primary rat motoneurons to alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) is an established in vitro model of excitotoxic motoneuron death. Here we show that leupeptin treatment improved motoneuron survival following exposure to AMPA (50 microM). Application of leupeptin (100 microM) to AMPA treated cultures rescued many motoneurons so that 74% (+/-3.4 S.E.M., n=5) survived compared with only 49% (+/-2.4 S.E.M., n=5) in untreated cultures. The effect of treatment with leupeptin on motoneuron survival and muscle function was also examined in vivo. In 3 day-old rats, the sciatic nerve was crushed and at the time of injury, a silicon implant containing leupeptin was inserted onto the lumbar spinal cord. The effect on long-term motoneuron survival and muscle function was assessed 12 weeks after injury. The results showed that there was long-term improvement in motoneuron survival in the leupeptin treated group. Thus, in untreated animals 12 weeks after nerve crush only 30% (+/-2.8. S.E.M., n=3) of sciatic motoneurons survived compared with 43% (+/-1.5 S.E.M., n=3) in the leupeptin-treated group. This improvement in motoneuron survival was reflected in a significant improvement in muscle function in the leupeptin-treated group. For example in the soleus muscle of treated rats 20.8 (+/-1.40 S.E.M., n=5) motor units survived compared with only 14.6 (+/-1.21 S.E.M., n=5) in untreated animals. Thus, treatment with leupeptin, a calpain inhibitor, rescues motoneurons from cell death and improves muscle function following nerve injury.

Fas and Fas-associated death domain protein regulate monocyte chemoattractant protein-1 expression by human smooth muscle cells through caspase- and calpain-dependent release of interleukin-1alpha

We previously reported that treatment of human vascular smooth muscle cells (SMCs) with proapoptotic stimuli, including Fas ligand plus cycloheximide (FasL/Chx), or overexpression of Fas-associated death domain protein (FADD) result in increased expression of monocyte chemoattractant protein-1 (MCP-1) and other proinflammatory genes. In this study, we demonstrate that Fas/FADD-induced MCP-1 upregulation is driven by an autocrine/paracrine signaling loop in which interleukin (IL)-1alpha synthesis and release are activated through caspase- and calpain-dependent processes. Untreated SMCs contain very little IL-1alpha protein or transcript. Both were increased greatly in response to Fas/FADD activation, primarily through an autocrine/paracrine pathway in which secreted IL-1alpha stimulated additional IL-1alpha synthesis and release. Caspase 8 (Csp8) activity increased in response to FasL/Chx treatment, and Csp8 inhibitors markedly reduced IL-1alpha release and MCP-1 upregulation. In contrast, Csp8 activity was not significantly increased in response to FADD overexpression and caspase inhibitors did not effect FADD-induced MCP-1 upregulation. Both FasL/Chx treatment and FADD overexpression increased the activity of calpains. Calpain inhibitors reduced IL-1alpha release and MCP-1 upregulation in both FADD-overexpressing SMCs and FasL/Chx-treated SMCs without blocking Csp8 activity. This indicates that calpains are not required for activation of caspases and that caspase activation is not sufficient for IL-1alpha release and MCP-1 upregulation. These data suggest that calpains play a dominant role in Fas/FADD-induced IL-1alpha release and MCP-1 upregulation and that caspase activation may function to amplify the effects of calpain activation.

S100A13 mediates the copper-dependent stress-induced release of IL-1alpha from both human U937 and murine NIH 3T3 cells

Copper is involved in the promotion of angiogenic and inflammatory events in vivo and, although recent clinical data has demonstrated the potential of Cu2+ chelators for the treatment of cancer in man, the mechanism for this activity remains unknown. We have previously demonstrated that the signal peptide-less angiogenic polypeptide, FGF1, uses intracellular Cu2+ to facilitate the formation of a multiprotein aggregate that enables the release of FGF1 in response to stress and that the expression of the precursor form but not the mature form of IL-1alpha represses the stress-induced export of FGF1 from NIH 3T3 cells. We report here that IL-1alpha is a Cu2+-binding protein and human U937 cells, like NIH 3T3 cells, release IL-1alpha in response to temperature stress in a Cu2+-dependent manner. We also report that the stress-induced export of IL-1alpha involves the intracellular association with the Cu2+-binding protein, S100A13. In addition, the expression of a S100A13 mutant lacking a sequence novel to this gene product functions as a dominant-negative repressor of IL-1alpha release, whereas the expression of wild-type S100A13 functions to eliminate the requirement for stress-induced transcription. Lastly, we present biophysical evidence that IL-1alpha may be endowed with molten globule character, which may facilitate its release through the plasma membrane. Because Cu2+ chelation also represses the release of FGF1, the ability of Cu2+ chelators to potentially serve as effective clinical anti-cancer agents may be related to their ability to limit the export of these proinflammatory and angiogenic signal peptide-less polypeptides into the extracellular compartment.

IL-1 alpha, innate immunity, and skin carcinogenesis: the effect of constitutive expression of IL-1 alpha in epidermis on chemical carcinogenesis

Tumor promoters such as the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) are proinflammatory agents, and their mechanism of action in epithelial carcinogenesis has been linked to the release of IL-1 alpha and the induction of chronic inflammation in skin. To test the role of IL-1 alpha and inflammation in models of cutaneous carcinogenesis, we used our previously described FVB/N transgenic mice overexpressing 17-kDa IL-1 alpha in the epidermis under the keratin 14 (K14) promoter. Strikingly, the K14/IL-1 alpha mice were completely resistant to papilloma and carcinoma formation induced by a two-stage DMBA/TPA protocol, while littermate controls developed both tumor types. K14/IL-1 alpha mice crossed with the highly sensitive TG.AC mice, constitutively expressing mutant Ha-Ras, also failed to develop papillomas or carcinomas. When the K14/IL-1 alpha transgene was bred onto a recombinase-activating gene-2-deficient background, the resistance persisted, indicating that innate, but not acquired, mechanisms may be involved in the resistance to the initiation/promotion model. As an alternative approach, a complete carcinogenesis protocol using repetitive application of DMBA alone was applied. Surprisingly, although the IL-1 alpha mice still did not develop papillomas, they did develop carcinomas de novo at an accelerated rate compared with controls. We conclude that constitutive IL-1 alpha expression rendered FVB mice completely resistant to carcinomas that required evolution from prior papillomas, but facilitated carcinomas that did not evolve from papillomas, as in the complete carcinogenesis protocol. Thus, the role of IL-1 alpha and, by extension that of other proinflammatory factors, in epithelial carcinogenesis are more complex than previously appreciated. These mice may provide a mechanism to investigate the validity of these models of human skin tumorigenesis.

The mystery of nonclassical protein secretion. A current view on cargo proteins and potential export routes

Most of the examples of protein translocation across a membrane (such as the import of classical secretory proteins into the endoplasmic reticulum, import of proteins into mitochondria and peroxisomes, as well as protein import into and export from the nucleus), are understood in great detail. In striking contrast, the phenomenon of unconventional protein secretion (also known as nonclassical protein export or ER/Golgi-independent protein secretion) from eukaryotic cells was discovered more than 10 years ago and yet the molecular mechanism and the molecular identity of machinery components that mediate this process remain elusive. This problem appears to be even more complex as several lines of evidence indicate that various kinds of mechanistically distinct nonclassical export routes may exist. In most cases these secretory mechanisms are gated in a tightly controlled fashion. This review aims to provide a comprehensive overview of our current knowledge as a basis for the development of new experimental strategies designed to unravel the molecular machineries mediating ER/Golgi-independent protein secretion. Beyond solving a fundamental problem in current cell biology, the molecular analysis of these processes is of major biomedical importance as these export routes are taken by proteins such as angiogenic growth factors, inflammatory cytokines, components of the extracellular matrix which regulate cell differentiation, proliferation and apoptosis, viral proteins, and parasite surface proteins potentially involved in host infection.

Suppression of oxidative stress-induced hepatocyte injury by calpain antisense

BACKGROUND

Calpain, a cytosolic Ca(2+)-dependent proteinase, plays a pivotal role in cell injury. In this study, we investigated the effect of calpain-mu antisense oligonucleotide on oxidative stress induced-hepatocyte injury.

MATERIALS AND METHODS

Hemagglutinating virus of Japan liposome complex with one of three types of antisense oligonucleotide (AS-1, AS-2, AS-3) or scramble oligonucleotide was added to the culture medium of HuH7 cells and incubated for 6 days. The expression of calpain-mu protein was examined by Western blotting. After the addition of tert-butyl hydroperoxide, bleb formation was examined by phase contrast microscopy, and cell viability was assessed by the release of lactate dehydrogenase.

RESULTS

Incubation of HuH7 cells with AS-2 resulted in a decrease in the amount of calpain on day 4 and a further decrease to almost undetectable levels on day 6, whereas scramble oligonucleotide had no effect. Bleb formation was observed 120 min after the addition of tert-butyl hydroperoxide in scramble oligonucleotide-treated cells as in untreated cells. In contrast, it was rarely observed in AS-2-treated cells. Lactate dehydrogenase release was significantly suppressed in AS-2-treated cells, compared with that in scramble oligonucleotide treated-cells.

CONCLUSIONS

Our findings suggest that calpain activation is involved in the pathogenesis of oxidative stress injury and that transfection of calpain antisense may potentially protect against ischemia/reperfusion liver injury.

Intracellular interleukin-1 receptor antagonist in osteoarthritis chondrocytes

The objective of the current study was to determine whether the balance of interleukin-1 and intracellular interleukin-1 receptor antagonist in chondrocytes in osteoarthritic human joints favors agonist action. Chondrocytes were isolated from cartilage specimens taken at the time of joint arthroplasty. Interleukin-1alpha, interleukin-1beta, and intracellular interleukin-1 receptor antagonist messenger ribonucleic acids were assessed by reverse transcriptase-polymerase chain reaction, and chondrocyte lysates were analyzed by enzyme-linked immunosorbent assay for the respective proteins. Type I intracellular interleukin receptor antagonist transcripts were the only intracellular variant detected in osteoarthritis chondrocytes. In cartilage graded as advanced osteoarthritis both interleukin proteins in chondrocyte lysates decreased, correlating with decreased interleukin-1alpha and beta messenger ribonucleic acids. Interleukin-1 receptor antagonist exceeded interleukin-1alpha in chondrocyte lysates by one order of magnitude except that in moderate osteoarthritis, antagonist was only two- to fourfold in excess. Interleukin-1alpha and interleukin-1beta proteins were correlated closely in individual lysates, with interleukin-1beta exceeding interleukin-1beta by one order of magnitude. In moderately degenerated cartilage, intracellular antagonist may not be sufficiently abundant to block postulated intracellular functions of precursor interleukin-1alpha. Furthermore, if stored interleukin-1alpha, interleukin-1beta, and interleukin receptor antagonist are released from chondrocytes, the localized antagonist would be insufficient to prevent signaling through cell surface receptors. Chondrocyte-derived interleukin-1alpha and interleukin-1beta may locally overwhelm inhibition by interleukin receptor antagonist to promote the early degenerative changes in osteoarthritis.

Inflammatory mechanisms associated with brain damage induced by kainic acid with special reference to the interleukin-1 system

The evidence of inflammatory processes in the clinical manifestations and neuropathological sequelae of epilepsy have accumulated in the last decade. Administration of kainic acid, an analogue of the excitatory amino acid glutamate, induces a characteristic behavioural syndrome and a reproducible pattern of neurodegeneration in several brain areas, closely resembling human temporal lobe epilepsy. Results from studies using the kainic acid model indicate that manipulation of pro- and anti-inflammatory cytokines can modify the outcome with regard to the behavioural syndrome as well as the neuropathological consequences. Interleukin-1 is one of the most important cytokines and has several actions in the brain that are critical for the host defense against injury and infection, and it is involved in the initiation of early stages of inflammation. It is believed that interleukin-1 plays a pivotal role in the neuroinflammation associated with certain forms of neurodegeneration, including cerebral ischemia, trauma and excitotoxic brain injury. In this review, we have summarized the experimental data available with regard to the involvement of the interleukin-1 system in kainic acid-induced changes in the brain and emphasized the modulatory role of interleukin-1beta in this model of epilepsy

Expression and regulation of the prointerleukin-1alpha processing enzymes calpain I and II in the rat testis

Interleukin-1alpha (IL-1alpha) is constitutively expressed in an age- and stage-dependent manner by rat Sertoli cells. However, the mechanism of regulation of IL-1alpha is unclear in testis. We studied this regulation at the level of the enzyme calpain, a potential regulator that cleaves 32 kDa proIL-1alpha to produce mature 17 kDa IL-1alpha. Both calpain I and II were found to cleave recombinant rat testis 32proIL-1alpha in vitro. A temporary age-related increase in messenger RNA (mRNA) levels of calpain I was found in testis of 20- and 25-day-old rats, coinciding with important events of spermatogenesis and a gradual increase in IL-1alpha, while calpain II expression was constant. In response to lipopolysaccharide (LPS), calpain I protein levels were down-regulated in the seminiferous tubules, while calpain II was less affected. By contrast, the liver after LPS treatment showed up-regulated calpain I and II immunoreactive protein and reverse transcriptase chain reaction (RT-PCR) signal. Depleting Leydig cells by ethane 1,2-dimethane sulphonate treatment resulted in down-regulated calpain I mRNA and protein expression, whereas calpain II remained unchanged. In summary, there is a differential expression of calpain I and II under pathological conditions induced either by endotoxin stimuli or Leydig cell depletion, which may produce a differential effect on IL-1alpha processing.

Evolution of interleukin-1beta

All jawed vertebrates possess a complex immune system, which is capable of anticipatory and innate immune responses. Jawless vertebrates possess an equally complex immune system but with no evidence of an anticipatory immune response. From these findings it has been speculated that the initiation and regulation of the immune system within vertebrates will be equally complex, although very little has been done to look at the evolution of cytokine genes, despite well-known biological activities within vertebrates. In recent years, cytokines, which have been well characterised within mammals, have begun to be cloned and sequenced within non-mammalian vertebrates, with the number of cytokine sequences available from primitive vertebrates growing rapidly. The identification of cytokines, which are mammalian homologues, will give a better insight into where immune system communicators arose and may also reveal molecules, which are unique to certain organisms. Work has focussed on interleukin-1 (IL-1), a major mediator of inflammation which initiates and/or increases a wide variety of non-structural, function associated genes that are characteristically expressed during inflammation. Other than mammalian IL-1beta sequences there are now full cDNA sequences and genomic organisations available from bird, amphibian, bony fish and cartilaginous fish, with many of these genes having been obtained using an homology cloning approach. This review considers how the IL-1beta gene has changed through vertebrate evolution and whether its role and regulation are conserved within selected non-mammalian vertebrates.

Induction of thermal and chemical stability of O6-methylguanine-DNA methyltransferase by Ca2+

Divalent cations stabilized rat recombinant O6-methylguanine-DNA methyltransferase (rMGMT) protein against heat treatment. Activity of rMGMT was completely abolished by incubating at 45 degrees C for 30 min, however, addition of 1.0 mM Mg2+, Ca2+ or Mn2+ significantly protected heat-induced inactivation of MGMT activity (50-60% vs. 97% inactivation). Protective effect of Ca2+ on the MGMT activity was concentration-dependent up to 3 mM, and the thermal protection was effective up to 45 degrees C. In order to investigate Ca2+ binding site in rMGMT protein, truncated GST-rMGMT proteins containing N-terminal 39 amino acids (GST-rMGMT39), 70 amino acids (GST-rMGMT70) and full-length protein (GST-rMGMT) were prepared. Radiolabeled calcium ion [45Ca2+] was bound only to the GST-rMGMT70 and GST-rMGMT, but not to the GST-rMGMT39, indicating that divalent cations could bind the residues between 40th and 70th of the rMGMT protein. Calcium binding was not observed in the site-directed mutant rMGMT proteins (rMGMT(D42A) and rMGMT(E45A)), confirmed by autoradiography using [45Ca2+] after nondenaturing gel electrophoresis; however, the above two mutants had the same catalytic activity as well as proteolytic sensitivity as the wild MGMT protein. Analysis by equilibrium dialysis revealed stoichiometric binding of one molecule of Ca2+ to one molecule of the protein. Since circular dichroism (CD) spectra indicated no discernible difference before and after Ca2+ binding, the above results suggested that neutralization of two negative charges of Asp42 and Glu45 by Ca2+ resulted in thermal stabilization of the protein with minimum perturbation of its tertiary structure.

Alternative splice variants of doublecortin-like kinase are differentially expressed and have different kinase activities

Alternative splicing of mRNA transcripts expands the range of protein products from a single gene locus. Several splice variants of DCLK (doublecortin-like kinase) have previously been reported. Here, we report the genomic organization underlying the splice variants of DCLK and examine the expression profile of two splice variants affecting the kinase domain of DCLK and CPG16 (candidate plasticity gene 16), one containing an Arg-rich domain and the other affecting the C terminus of the protein. These splice alternatives were differentially expressed in embryonic and adult brain. Both splice variants disrupted DCLK PEST domains; however, all splice variants remained sensitive to proteolysis by calpain. The adult-specific C-terminal splice variant of DCLK had reduced autophosphorylation activity, but similar kinase activity for myelin basic protein relative to the embryonic splice variant. The splice variant adding an Arg-rich domain gained an autophosphorylation site at Ser-382. Although this protein isoform was expressed mainly in the adult brain, the phosphorylated form was strongly enriched in embryonic brain and adult olfactory bulb, suggesting a possible role in migrating neurons.

The role of calpain in caspase activation during etoposide induced apoptosis in T cells

T cells treated with the drug etoposide undergo apoptotic death characterized by early evidence of nuclear damage followed by loss of mitochondrial integrity and cell lysis. Calpains and caspases are cytoplasmic proteases and there is increasing evidence of cross-talk between these proteases in death pathways. In this study we have investigated the role of calpain, in etoposide-triggered apoptosis in the 2B4 murine T cell hybridoma. Cell permeable inhibitors of calpain, ALLnM, E64 and calpeptin that block Fas ligand-Fas-mediated death in T cells, blocked etoposide-induced nuclear damage, loss of mitochondrial integrity and cell lysis. A broad spectrum peptide inhibitor of caspases, ZVAD-fmk, partially blocked nuclear damage but poorly inhibited mitochondrial damage or cell lysis triggered by etoposide. Etoposide-induced expression of the cleaved, proteolytically active form of caspase 3, and DEVD-ase activity, detected prior to nuclear damage, were blocked in the presence of calpain inhibitors. Collectively, these data describe a role for calpain in regulating etoposide-induced apoptosis via a caspase-dependent pathway in T cells.