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Altered adipose tissue may contribute to the longevity of Snell dwarf and growth hormone receptor (GHR) knock-out mice. We report here that white (WAT) and brown (BAT) fat have elevated UCP1 in both kinds of mice, and that adipocytes in WAT depots turn beige/brown. These imply increased thermogenesis and are expected to lead to improved glucose control. Both kinds of long-lived mice show lower levels of inflammatory M1 macrophages and higher levels of anti-inflammatory M2 macrophages in BAT and WAT, with correspondingly lower levels of TNFα, IL-6, and MCP1. Experiments with mice with tissue-specific disruption of GHR showed that these adipocyte and macrophage changes were not due to hepatic IGF1 production nor to direct GH effects on adipocytes, but instead reflect GH effects on muscle. Muscles deprived of GH signals, either globally (GKO) or in muscle only (MKO), produce higher levels of circulating irisin and its precursor FNDC5. The data thus suggest that the changes in adipose tissue differentiation and inflammatory status seen in long-lived mutant mice reflect interruption of GH-dependent irisin inhibition, with consequential effects on metabolism and thermogenesis.

In order to adapt to the low temperature environment, organisms transmit excitement to the central system through the thermal sensing system, which is a classic reflex reaction. The cold receptor GLR-3 perceives cold and pro duces cold avoidance behavior through peripheral sensory neurons ASER. In order to further understand the gene encoding of the cold sensing glr-3 gene and the evolution of its homologous gene group function and protein function, the nucleotide sequence and amino acid sequence of the glr-3 gene and its homologous gene in 24 species were obtained and compared. By clustering with the GRIK2 gene sequence of Rana chensinensis, the bio informatics method was used to predict and sequence analyze the change of gene, evolution rate, physical and chemical properties of protein, glycosyla tion sites, phosphorylation sites, secondary structure and tertiary structure of protein. The analysis results show that the glr-3 gene and its homologous gene have obvious positive selection effect. The protein prediction analysis showed that the glr-3 gene and its homologous genes encoded proteins in these 25 species were hydrophilic proteins, and the proportion of side chains of aliphatic amino acids was high. The transmembrane helix was widespread and there were more N-glycosylation sites and O-glycosylation sites. The protein phosphorylation sites encoded were serine, threonine and tyrosine phosphorylation sites. Secondary structure prediction showed that the secondary structure units of the encoded protein were α-helix, β-turn, random coil and extended chain, and the proportion of α-helix was the larg est. This study provides useful information on the evolution and function of the cold sensing gene glr-3 and its homologous genes.

To investigate the effect of miR-223 on thyroid cancer cells, further to study its potential mechanisms. The difference in miR-223 expression between normal thyroid Nthy-ori3-l cells and thyroid cancer SW579 cells was detected by PCR. The miR-223 overexpression and silencing vector transfection were verified by qRT-PCR. To further investigate the role of miR-223 in AQP-1, the AQP-1 siRNA vector was transfected on the basis of transfection of miR-223 inhibitor vector. The cell proliferation was detected by plate cloning, MTT, and cellular immunofluorescence assays. Cell cycle and apoptosis were detected by flow cytometry. Western blot was used to detect the expression of AQP-1 protein. The expression of miR-223 in SW579 cells was higher than that in normal cells. After transfection with miR-223 mimic, miR-223 expression was increased in SW579 cells. MiR-223 inhibitor transfection can inhibit SW579 cells proliferation, promote apoptosis, and inhibit cell cycle G0/G1 arrest. The SW579 cells proliferation was decreased, and the apoptosis rate was increased after transfection of AQP-1 silencing vector. Compared with the AQP-1 siRNA group, the SW579 cells proliferation rate was further reduced, and the apoptosis rate was significantly increased after co-transfection of miR-223 silencing vector and AQP-1 silencing vector. AQP-1 protein was highly expressed in SW579 cells, and miR-223 inhibitor can down-regulate the expression of APQ-1 protein. The expression AQP-1 protein was significantly reduced after transfected with AQP-1 silencing vector. Inhibition of miR-223 expression could suppress proliferation and promote apoptosis of SW579, and its mechanism is related to down-regulation of APQ-1 protein expression.

Cadmium (Cd) accumulates with aging and is elevated in long-lived species. Metallothioneins (MTs), small cysteine-rich proteins involved in metal homeostasis and Cd detoxification, are known to be related to longevity. However, the relationship between Cd accumulation, the role of MTs, and aging is currently unclear. Specifically, we do not know if long-lived species evolved an efficient metal stress response by upregulating their MT levels to reduce the toxic effects of environmental pollutants, such as Cd, that accumulate over their longer life span. It is also unknown if the number of MT genes, their expression, or both protect the organisms from potentially damaging effects during aging. To address these questions, we reanalyzed several cross-species studies and obtained data on MT expression and Cd accumulation in long-lived mouse models. We confirmed a relationship between species maximum life span in captive mammals and their Cd content in liver and kidney. We found that although the number of MT genes does not affect longevity, gene expression and protein amount of specific MT paralogs are strongly related to life span in mammals. MT expression rather than gene number may influence the high Cd levels and longevity of some species. In support of this, we found that overexpression of MT-1 accelerated Cd accumulation in mice and that tissue Cd was higher in long-lived mouse strains with high MT expression. We conclude that long-lived species have evolved a more efficient stress response by upregulating the expression of MT genes in presence of Cd, which contributes to elevated tissue Cd levels. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11357-021-00393-3.

Colorectal cancer (CRC) is one of the most prevalent cancers due to its frequency and high rate of mortality. Polyamine-vectorized anticancer drugs possess multiple biological properties. Of these drugs, 9F has been shown to inhibit tumor growth and the metastasis of hepatocellular carcinoma. This current study aims to investigate the effects of 9F on CRC and determine its molecular mechanisms of action. Our findings demonstrate that 9F inhibits CRC cell growth by inducing apoptosis and cell cycle arrest, and suppresses migration, invasion and angiogenesis in vitro, resulting in the inhibition of tumor growth and metastasis in vivo. Based on RNA-seq data, further bioinformatic analyses suggest that 9F exerts its anticancer activities through p53 signaling, which is responsible for the altered expression of key regulators of the cell cycle, apoptosis, the epithelial-to-mesenchymal transition (EMT), and angiogenesis. In addition, 9F is more effective than amonafide against CRC. These results show that 9F can be considered as a potential strategy for CRC treatment.

Background Colorectal cancer (CRC) is one of the most common malignancies worldwide. Metastasis is the major cause of death in patients with CRC. Lycorine, the phenanthridine alkaloid most commonly found in spp of the Amaryllidaceae family, has shown promising anticancer activities with minor side effects. However, the effects and the detailed mechanism of lycorine against metastasis of CRC remains unclear. Study design/methods The purpose of this study was to investigate the effects of lycorine on CRC and characterize the molecular mechanisms observed in lycorine-treated CRC cells using RNA-sequencing. MTT assay, colony formation assay, acridine orange/ethidium bromide (AO/EB) staining and Annexin V-FITC/Propidium iodide (PI) staining were conducted to examine the effects of lycorine on cell proliferation and apoptosis in CRC cells. RNA sequencing, real-time PCR assays and western blot were performed. Migration and invasion abilities of lycorine-treated CRC cells were investigated by wound healing and transwell invasion assays. The mouse CRC lung metastasis model was established and was used to detect the effect of lycorine on CRC in vivo. Results Our results demonstrated that lycorine inhibited the proliferation and colony formation of CRC cells in a concentration-dependent manner. AO/EB staining and Annexin V-FITC/PI staining showed that lycorine induced apoptosis in a concentration-dependent manner. Lycorine also reduced lung metastasis of CRC in vivo. Moreover, transcriptomic analysis suggested that lycorine regulated the expression of 3556 genes. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway was implicated according to the differentially expressed genes (DEGs), and multiple pathways including those of mitogen-activated protein kinase (MAPK), relaxin, Ras, phosphatidylinositol 3‑kinase (PI3K)-protein kinase B (Akt) and Wnt/β-catenin were selected by functional enrichment analyses. Furthermore, based on transcriptomic analysis, we found that the tumor necrosis factor (TNF) pathway and endoplasmic reticulum stress were responsible for lycorine-induced apoptosis. Conclusions These results obtained in this study demonstrated that lycorine has the potential to suppress CRC in vitro and in vivo through the lycorine-regulated multiple signaling pathways.

Biological aging is the dominant risk factor for most chronic diseases. Development of anti-aging interventions offers the promise of preventing many such illnesses simultaneously. Cellular stress resistance is an evolutionarily conserved feature of longevity. Here, we identify compounds that induced resistance to the superoxide generator paraquat (PQ), the heavy metal cadmium (Cd), and the DNA alkylator methyl methanesulfonate (MMS). Some rescue compounds conferred resistance to a single stressor, while others provoked multiplex resistance. Induction of stress resistance in fibroblasts was predictive of longevity extension in a published large-scale longevity screen in C. elegans. Transcriptomic analysis implicated Nrf2 signaling in stress resistance provided by two protective compounds, cardamonin and AEG 3482. Molecules that conferred stress resistance also induced cellular inflammatory pathways, and other core pathways such as AMPK signaling. Small molecules identified in this work may represent attractive candidates to evaluate for their potential pro-health and pro-longevity effects in mammals.

Naphthalenetetracarboxylic diimide (NDI) is widely used as a photoelectric material in the field of medicine. A series of asymmetric naphthalene diimide derivatives were synthesized and evaluated for their anticancer properties by various experimental assays. As the representative compound, 3c exerted significantly greater inhibitory effects on hepatoma cells SMMC-7721 and Hep G2 with an IC(50) value of 1.48 ± 0.43 μM and 1.70 ± 0.53 μM, respectively, than normal hepatocytes QSG-7701 with an IC(50) value of 7.11 ± 0.08 μM. Treatment with compound 3c (3 μM) for 48 h resulted in apoptosis of SMMC-7721 cells and Hep G2 cells with 52.1% and 67.8% apoptotic cells, respectively. Compound 3c induced autophagy and suppressed the migration of hepatoma cells in a concentration-dependent manner, resulting from the generation of reactive oxygen species (ROS). Based on its biological ability, compound 3c was considered as a potent anticancer agent.

ATF4, a DNA-binding factor that modulates responses to amino acid availability and ribosomal function, has been shown to be altered in both liver and fibroblasts from two strains of long-lived mice, i.e. Snell dwarf and PAPP-A knockout mice. New data now show elevated ATF4 levels, and elevation of ATF4-dependent proteins and mRNAs, in liver of mice treated with acarbose or rapamycin, calorically restricted mice, methionine-restricted mice, and mice subjected to litter crowding. Elevation of ATF4, at least in liver, thus seems to be a shared feature of diets, drugs, genes, and developmental alterations that extend maximum lifespan in mice.

Peritrophic membranes (PMs) are composed of chitin and protein. Chitin and protein play important roles in the structural formation and function of the PM. A new type I PM protein, HoCBP76, was identified from the Holotrichia oblita. HoCBP76 was shown as a 62.3 kDa protein by SDS-PAGE analysis and appeard to be associated with the PM throughout its entire length. In H. oblita larvae, the midgut is the only tissue where HoCBP76 could be detected during the feeding period of the larvae. The predicted amino acid sequence indicates that it contains seven tandem chitin binding domains belonging to the peritrophin-A family. HoCBP76 has chitin binding activity and is strongly associated with the PM. The HoCBP76 was not a mucin-like glycoprotein, and the consensus of conserved cysteines appeared to be CX13–17CX5CX9CX12CX7C. Western blot analysis showed that the abundance of HoCBP76 in the anterior, middle and posterior regions of the midgut was similar, indicating that HoCBP76 was secreted by the whole midgut epithelium, and confirmed the H. oblita PM belonged to the Type I PM. Immunolocalization analysis showed that HoCBP76 was mainly localized in the PM. The HoCBP76 is the first PM protein found in the H. oblita; however, its biochemical and physiological functions require further investigation.

In a previous study, we found that the global genome organizer Special AT-rich binding protein 1 (SATB1) is highly expressed in mesenchymal-derived human osteosarcoma U2OS cells and that the knock-down of SATB1 results in the inhibition of cell proliferation. The present study was aimed at investigating the effect of silencing SATB1 on cell migration, invasion, apoptosis and resistance to the chemotherapeutic drug arsenic trioxide. Cell migration and invasion were detected by wound-healing assays and trans-well invasion assays, respectively. Cell apoptosis was analyzed by an in situ Cell Death Detection POD Kit, based on terminal deoxynucleotydyl transferase mediated dUTP nick-end labeling (TUNEL) staining and mRNAs were analyzed by real time qRT-PCR. We found that cell migration and invasion were inhibited and that the proportion of apoptotic cells and sensitivities to the chemotherapeutic drug arsenic trioxide were enhanced by knockdown of SATB1 in U2OS cells. Furthermore, mRNA of ABCC1 and ABCG2 were decreased strikingly after SATB1 silencing. It was concluded that the elevated expression of SATB1 in U2OS cells contributes to maintenance of the malignant phenotype and resistance to chemotherapeutic drugs ATO, suggesting that silencing SATB1 in the cells might improve the effects of arsenic trioxides in the treatment of osteosarcoma in which SATB1 is over-expressed and that ABCC1 and ABCG2 were involved in SATB1 mediated resistance of U2OS cells to ATO.

Detoxification of ingested xenobiotic chemicals, and of potentially toxic endogenous metabolites, is carried out largely through a series of enzymes synthesized in the liver, sometimes called “xenobiotic metabolizing enzymes” (XME). Expression of these XME is sexually dimorphic in rodents and humans, with many of the XME expressed at higher levels in females. This expression pattern is thought to be regulated, in part, by the sex differences in circadian growth hormone (GH) pulsatility. We have evaluated mRNA, in the liver, for 52 XME genes in male and female mice of four mutant stocks, with diminished levels of GH receptor (GHR) either globally (GKO), or in liver (LKO), fat (FKO), or muscle (MKO) tissue specifically. The data show complex, sex-specific changes. For some XME, the expression pattern is consistent with direct control of hepatic mRNA by GHR in the liver. In contrast, other XME show evidence for indirect pathways in which hepatic XME expression is altered by GH signals in fat or skeletal muscle. The effects of GHR-null mutations on glucose control, responses to dietary interventions, steroid metabolism, detoxification pathways, and lifespan may depend on a mixture of direct hepatic effects and cross talk between different GH-responsive tissues.

There are multiple mechanisms that protect the intestine from an excessive inflammatory response to intestinal microorganisms. We report here that all four mammalian peptidoglycan recognition proteins (PGRPs or Pglyrps) protect the host from colitis induced by dextran sulfate sodium (DSS). Pglyrp1(-/-), Pglyrp2(-/-), Pglyrp3(-/-), and Pglyrp4(-/-) mice are all more sensitive than wild-type mice to DSS-induced colitis due to a more inflammatory gut microflora, higher production of interferon-gamma, higher expression of interferon-inducible genes, and an increased number of NK cells in the colon upon initial exposure to DSS, which leads to severe hyperplasia of the lamina propria, loss of epithelial cells, and ulceration in the colon. Thus, during experimental colitis, PGRPs protect the colon of wild-type mice from an early inflammatory response and the loss of the barrier function of intestinal epithelium by promoting normal bacterial flora and by preventing damaging production of interferon-gamma by NK cells in response to injury.

Mammals have four peptidoglycan recognition proteins (PGRPs or PGLYRPs), which are secreted innate immunity pattern recognition molecules with effector functions. In this study, we demonstrate that human PGLYRP-1, PGLYRP-3, PGLYRP-4, and PGLYRP-3:4 have Zn2+-dependent bactericidal activity against both Gram-positive and Gram-negative bacteria at physiologic Zn2+ concentrations found in serum, sweat, saliva, and other body fluids. The requirement for Zn2+ can only be partially replaced by Ca2+ for killing of Gram-positive bacteria but not for killing of Gram-negative bacteria. The bactericidal activity of PGLYRPs is salt insensitive and requires N-glycosylation of PGLYRPs. The LD99 of PGLYRPs for Gram-positive and Gram-negative bacteria is 0.3–1.7 μM, and killing of bacteria by PGLYRPs, in contrast to killing by antibacterial peptides, does not involve permeabilization of cytoplasmic membrane. PGLYRPs and antibacterial peptides (phospholipase A2, α- and β-defensins, and bactericidal permeability-increasing protein), at subbactericidal concentrations, synergistically kill Gram-positive and Gram-negative bacteria. These results demonstrate that PGLYRPs are a novel class of recognition and effector molecules with broad Zn2+-dependent bactericidal activity against both Gram-positive and Gram-negative bacteria that are synergistic with antibacterial peptides.

Skin and mucous membranes come in contact with external environment and protect tissues from infections by producing antimicrobial peptides. We report that human peptidoglycan recognition proteins 3 and 4 (PGLYRP3 and PGLYRP4) are secreted as 89-115-kDa disulfide-linked homo- and heterodimers and are bactericidal against several pathogenic and nonpathogenic transient, but not normal flora, Gram-positive bacteria. PGLYRP3 and PGLYRP4 are also bacteriostatic toward all other tested bacteria, which include Gram-negative bacteria and normal flora Gram-positive bacteria. PGLYRP3 and PGLYRP4 are also active in vivo and protect mice against experimental lung infection. In contrast to antimicrobial peptides, PGLYRPs kill bacteria by interacting with their cell wall peptidoglycan, rather than permeabilizing their membranes. PGLYRP3 and PGLYRP4 are expressed in the skin, eyes, salivary glands, throat, tongue, esophagus, stomach, and intestine. Thus, we have identified the function of mammalian PGLYRP3 and PGLYRP4, and show that they are a new class of bactericidal and bacteriostatic proteins that have different structures, mechanism of actions, and expression patterns than antimicrobial peptides.

Peptidoglycan recognition proteins (PGRPs) are pattern recognition molecules coded by up to 13 genes in insects and 4 genes in mammals. In insects PGRPs activate antimicrobial pathways in the hemolymph and cells, or are peptidoglycan (PGN)-lytic amidases. In mammals one PGRP is an antibacterial neutrophil protein. We report that human PGRP-L is a Zn2+-dependent N-acetylmuramoyl-l-alanine amidase (EC 3.5.1.28), an enzyme that hydrolyzes the amide bond between MurNAc and l-Ala of bacterial PGN. The minimum PGN fragment hydrolyzed by PGRP-L is MurNAc-tripeptide. PGRP-L has no direct bacteriolytic activity. The other members of the human PGRP family, PGRP-Ialpha, PGRP-Ibeta, and PGRP-S, do not have the amidase activity. The C-terminal region of PGRP-L, homologous to bacteriophage and bacterial amidases, is required and sufficient for the amidase activity of PGRP-L, although its activity (in the N-terminal delta1-343 deletion mutant) is reduced. The Zn2+ binding amino acids (conserved in PGRP-L and T7 amidase) and Cys-419 (not conserved in T7 amidase) are required for the amidase activity of PGRP-L, whereas three other amino acids, needed for the activity of T7 amidase, are not required for the activity of PGRP-L. These amino acids, although required, are not sufficient for the amidase activity, because changing them to the "active" configuration does not convert PGRP-S into an active amidase. In conclusion, human PGRP-L is an N-acetylmuramoyl-l-alanine amidase and this function is conserved in prokaryotes, insects, and mammals.

Greening of etiolated plants is predominantly stimulated by light but the complete molecular mechanism is still unknown. Multiple studies currently focus on the important physiological effects of heme oxygenase (HO)/carbon monoxide (CO) in plants. In this report, firstly, the role of HO/CO in light-induced de-etiolation process was investigated. We discovered that light could significantly increase HO activities, HO-1 gene expression, CO release, and chlorophyll accumulation, all of which were sensitive to zinc protoporphyrin (ZnPPIX), the potent inhibitor of HO-1, respectively. Both HO-1 inducer hematin (H) and CO aqueous solution were able to relieve etiolation in wheat seedling leaves under completely darkness by up-regulating endogenous HO/CO system, so as nitric oxide (NO) donor sodium nitroprusside (SNP) did. Similarly, endogenous NO production was also boost in response to light, SNP, hematin and CO aqueous solution in wheat seedling leaves. Additionally, the restoration of chlorophyll contents was blocked, when the inhibitor of mammalian nitric oxide synthase N(G)-nitro-L-arginine methylester hydrochloride (L-NAME) or the specific scavenger of NO 2-(4-carboxyphenyl)-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO) was added, respectively. Furthermore, the inducible effects of light were different from those of SNP, hematin, and CO on Pfr accumulation and PHYA transcripts. However, all of sodium nitroprusside (SNP), hematin, and CO could accelerate NO emission, which suggested that HO/CO in wheat seedlings de-etiolation under dark-light transition may have a cross talk with NO.

SummaryPeptidoglycan recognition proteins (PGRPs) are structurally conserved from insects to mammals. Insect PGRPs have diverse host-defense functions. Mammalian PGRPs PGLYRP-1, PGLYRP-3, and PGLYRP-4 have bactericidal activity, while PGLYRP-2 has amidase activity. To extend the known functions of mammalian PGRPs, we examined whether they have immunomodulating activities in peptidoglycan-induced arthritis in mice. We demonstrate that PGLYRP-2 and Nod2 are both required for arthritis in this model. The sequence of events in peptidoglycan-induced arthritis is activation of Nod2, local expression of PGLYRP-2, chemokine production, and recruitment of neutrophils into the limbs, which induces acute arthritis. Only PGLYRP-2 among the four mammalian PGRPs displays this proinflammatory function, and PGLYRP-1 is anti-inflammatory. Toll-like receptor 4 (TLR4) and MyD88 are required for maturation of neutrophils before peptidoglycan challenge. Our results demonstrate that PGRPs, Nod2, and TLR4, representing three different types of pattern-recognition molecules, play interdependent in vivo roles in local inflammation.

Peptidoglycan recognition proteins (PGRPs) are structurally conserved through evolution, but their functions in innate immunity are different in invertebrates and vertebrates. We asked what the functions of PGRPs in fish are and whether they are indispensable for defense against infection, because fish are the first vertebrates that developed adaptive immunity, but still rely solely on innate immunity during early development of embryos. We identified and cloned three zebrafish PGRPs, and showed that they are highly expressed in eggs, developing embryos, and in adult tissues that contact external environment. Zebrafish PGRPs have both peptidoglycan-lytic amidase activity and broad-spectrum bactericidal activity, which is a unique feature. Furthermore, we demonstrated that in the developing zebrafish embryo one of these PGRPs is essential for defense and survival during bacterial infections. This is the first demonstration of an absolute requirement for innate immunity in defense against infections in fish embryos and for a PGRP protein for survival in vertebrates.

Human peptidoglycan recognition protein 2 (PGLYRP2) is an N-acetylmuramoyl-L-alanine amidase that hydrolyzes bacterial peptidoglycan and is differentially expressed in the two major organs in the human body, liver and skin. PGLYRP2 has a high constitutive expression in the liver but is not expressed in healthy human skin. PGLYRP2 mRNA is also not expressed in cultured human keratinocytes but is highly induced upon exposure to bacteria. In this study we identified the transcription start site for pglyrp2 and demonstrated that the differential expression of PGLYRP2 in hepatocytes and keratinocytes is regulated by different transcription factors whose binding sequences are located in different regions of the pglyrp2 promoter. Induction of pglyrp2 in keratinocytes is regulated by sequences in the distal region of the promoter and requires transcription factors NF-kappaB and Sp1, whereas constitutive expression of pglyrp2 in a hepatocyte cell line is regulated by sequences in the proximal region of the promoter and requires transcription factors c-Jun and ATF2. Regulation of constitutive and inducible expression of pglyrp2 is important for systemic and local innate immune responses to bacterial infections.

Skin protects host tissues from invasion by microorganisms. Skin was once regarded as a merely mechanical barrier due to its thick layer of keratinized epithelium (49). While this function is important, in recent years it has become clear that skin is rich in antimicrobial peptides and proteins, such as β-defensins (20, 21, 45), dermcidin (44), cathelicidin (12, 48), RNases (22), psoriasin (18), bactericidal permeability-increasing protein (51), and others (32, 63, 64). Healthy intact skin contains low levels of antimicrobial peptides and proteins. Breakage of the keratinized layer, however, may expose keratinocytes to high numbers of microorganisms, which induce production of antimicrobial peptides and proteins. Antimicrobial peptides and proteins are also produced in the skin in response to proinflammatory cytokines released from macrophages and dendritic cells stimulated by microorganisms or in some inflammatory disease processes, such as psoriasis (6, 12, 13, 18, 22, 29, 38, 45, 48, 63, 64). In addition to antimicrobial peptides and proteins, body secretions, such as sweat and tears, contain a bacteriolytic enzyme, lysozyme (EC 3.2.1.17). Lysozyme hydrolyzes the glycosidic bond between β(1-4)-linked N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) of peptidoglycan, a polymer uniquely present in the cell walls of virtually all bacteria (3, 50). Lysozyme by itself is bacteriolytic for only some gram-positive bacteria, but it acts synergistically with antimicrobial peptides enhancing their antibacterial effect. Digestion of peptidoglycan by lysozyme is also important in reducing peptidoglycan's proinflammatory activity (14). Mammals also have another enzyme that digests peptidoglycan, N-acetylmuramoyl-l-alanine amidase (EC 3.5.1.28), which is primarily present in the serum and which hydrolyzes the amide bond between MurNAc and l-Ala and thus removes stem peptides from the peptidoglycan molecule (5, 24, 36, 56-58). Digestion of peptidoglycan with amidase reduces or eliminates biologic activities of polymeric peptidoglycan (23, 34). We have recently demonstrated that human peptidoglycan recognition protein L (PGRP L) has N-acetylmuramoyl-l-alanine amidase activity (60). PGRPs are a family of pattern recognition molecules that were discovered first in insects (27, 62, 66) and then in mammals (7, 9, 27, 31). Insects have up to 17 different PGRP proteins that recognize peptidoglycan and bacteria and have several functions. They initiate activation of the prophenoloxidase cascade (which generates antimicrobial melanin and reactive oxygen species), activate Toll and Imd pathways (which induce production of antimicrobial peptides), participate in phagocytosis of bacteria, and are peptidoglycan-lytic enzymes (2, 7, 9, 27, 52, 62). Mammals have a family of four PGRPs, which were initially named PGRP-S, PGRP-L, and PGRP-Iα and PGRP-Iβ, by analogy to insect PGRPs (31); they were recently renamed peptidoglycan recognition protein 1 (PGLYRP1) PGLYRP2, PGLYRP3, and PGLYRP4, respectively, by the Human Genome Organization Gene Nomenclature Committee. Although mammalian PGLYRPs were initially thought of as pattern recognition receptors similar to insect PGRPs (7, 31), it is now becoming clear that they do not function as cell-surface receptors but more likely as effector molecules. Mammalian PGLYRP1 is present in granulocyte granules and has antibacterial properties (10, 30, 55), and mammalian PGLYRP2 is an N-acetylmuramoyl-l-alanine amidase (15, 60). PGLYRP2 is constitutively produced in the liver (31, 60) and is secreted into the bloodstream (68) but is not constitutively produced in other tissues. The aim of this study was to determine whether production of PGLYRP2 could be induced in other tissues that come in contact with bacteria and especially in the skin and the eyes.