STIM-mediated calcium influx regulates maintenance and selection of germinal center B cells

Positive selection of high-affinity germinal center (GC) B cells is driven by antigen internalization through their B cell receptor (BCR) and presentation to follicular helper T cells. However, the requirements of BCR signaling in GC B cells remain poorly understood. Store-operated Ca2+ entry, mediated by stromal interacting molecule 1 (STIM1) and STIM2, is the main Ca2+ influx pathway triggered by BCR engagement. Here, we showed that STIM-deficient B cells have reduced B cell competitiveness compared with wild-type B cells during GC responses. B cell-specific deletion of STIM proteins decreased the number of high-affinity B cells in the late phase of GC formation. STIM deficiency did not affect GC B cell proliferation and antigen presentation but led to the enhancement of apoptosis due to the impaired upregulation of anti-apoptotic Bcl2a1. STIM-mediated activation of NFAT was required for the expression of Bcl2a1 after BCR stimulation. These findings suggest that STIM-mediated survival signals after antigen capture regulate the optimal selection and maintenance of GC B cells.

Post-transplant Schizophyllum commune abscess in a pediatric patient with chronic granulomatous disease

Schizophyllum commune is a widely distributed basidiomycete fungus that occasionally causes sinusitis or allergic bronchopulmonary mycosis. The invasive infection mostly occurs in immunocompromised adults. The number of reports on S. commune infection have increased in this decade due to the expansion of diagnostic techniques and awareness in clinical practice. However, S.commune infection in patients with primary immunodeficiencies has not been reported yet. Here, we described S. commune-abscesses developed in the brain and lung of a boy with chronic granulomatous disease (CGD) after allogenic hematopoietic cell transplantation (HCT). A 12-year-old CGD patient developed febrile neutropenia from day 4 after HCT, followed by chest pain on day 23. He had no obvious infection before HCT. Diagnostic imaging revealed disseminated lung and brain abscesses. He received administration of voriconazole, and his symptoms improved after engraftment. Chronic administration of voriconazole had also a favorable therapeutic response to brain lesion. A part of the fungus ball exhaled by the patient was cultured to develop a filamentous fungus. S. commune was identified by the analysis of the 28S rRNA gene. The catalase test was positive for S. commune, indicating that S. commune had virulence in this patient with CGD. The assessment of specific-IgG to S. commune suggested peri-transplant infection, although colonization was not excluded. This rare pediatric case of S. commune infection highlights that CGD patients are vulnerable to invasive infection, especially when undergoing HCT.

Critical vitamin deficiencies in autism spectrum disorder: Reversible and irreversible outcomes

Vitamin deficiencies are an emerging concern in the management of children with autism spectrum disorder (ASD). Particular attention is required for recognizing the variable signs caused by unbalanced food intakes. We herein report two patients with multiple vitamin deficiencies who needed critical care showing different prognoses. Patient 1 with 'Shoshin' beriberi presenting with cardiac arrest had thiamine deficiency developed severe neurological sequelae despite rapid vitamin supplementation. Patient 2, who had leg pain and a limping gait, showed a rapid recovery with intravenous infusion and tube feeding after being diagnosed with scurvy. A literature search revealed several children with ASD with critically ill thiamine deficiency, but few reports documented a life-threatening condition in the form of cardiac arrest at the onset. Considering the high observation rate of food selectivity in children with ASD, early intervention is required to prevent the exacerbation of vitamin deficiencies to severe neurological disabilities.

Progressive B cell depletion in human MALT1 deficiency

Mucosa-associated lymphoid tissue lymphoma-translocation gene 1 (MALT1)-deficiency is a rare combined immunodeficiency characterized by recurrent infections, dermatitis and enteropathy. We herein investigate the immunological profiles of our patient and previously reported children with MALT1-deficiency. A mutation analysis was performed by targeted panel sequencing for primary immunodeficiency. Lymphocyte subset, activation and B cell differentiation were analyzed by flow cytometry and t-distributed stochastic neighbor embedding. Pneumocystis pneumonia developed in a 6-month-old Japanese infant with atopic dermatitis, enteritis and growth restriction. This infant showed agammaglobulinemia without lymphopenia. At 8 years of age, the genetic diagnosis of MALT1-deficiency was confirmed on a novel homozygous mutation of c.1102G>T, p.E368X. T cell stimulation tests showed impairments in the production of interleukin-2, phosphorylation of nuclear factor kappa B (NF-κB) p65 and differentiation of B cells. In combination with the literature data, we found that the number of circulatory B cells, but not T cells, were inversely correlated with the age of patients. The hematopoietic cell transplantation (HCT) successfully reconstituted the differentiation of mature B cells and T cells. These data conceptualize that patients with complete MALT1-deficiency show aberrant differentiation and depletion of B cells. The early diagnosis and HCT lead to a cure of the disease phenotype associated with the loss-of-function mutations in human CARD11.

Brain-sparing cord blood transplantation for the borderline stage of adrenoleukodystrophy

Background

Adrenoleukodystrophy (ALD) is an X-linked disorder characterized by rapidly progressive deterioration of neurocognitive functions and premature death. In addition to the difficulty in identifying the earliest signs of ALD, treatment-associated exacerbation of neurological symptoms has been an obstacle to achieve successful hematopoietic cell transplantation (HCT) for affected children.

Case report

We report a 9-year-boy with ALD. He presented with impairment in social skills compatible to the diagnosis of autism spectrum disorder from 3 years of age. He showed progressive strabismus, slurred speech and dysmetria at 6 years of age. The head MRI showed symmetrical T2-hyperintense lesions in the occipital white matters with a gadolinium enhancement, which extended to the internal capsules. The Loes score was thus calculated as 13. Very-long-chain-fatty-acids were increased to 1.800 (C24:0/C22:0) and 0.077 (C26:0/C22:0) in leukocytes. Sanger sequencing confirmed the pathogenic variant in ABCD1 (NM_000033.4:p.Gly512Ser). After multidisciplinary discussions over the treatment options, we performed a cord blood HCT with a reduced intensity conditioning (fludarabine, melphalan and brain-sparing total body irradiation). He was fully recovered with >90% chimerism of donor leukocytes at 55 days after HCT. He experienced three times of generalized seizures after discharge, that has been well controlled for 2 years without other complications or neurocognitive deteriorations.

Conclusion

For patients with ALD on a borderline indication for HCT, brain-sparing irradiation might be an alternative option in reduced intensity conditioning. Careful decision-making process and tailored conditioning are critical for the successful outcome of HCT for children with ALD.

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Therapeutic strategies remain to be established for adrenoleukodystrophy.

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Multidisciplinary discussions are necessary for making a decision of treatment.

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A 6-year-old boy achieved a successful engraftment after the transplantation.

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The brain-sparing method might provide favorable outcomes for adrenoleukodystrophy.

Cytomegalovirus-Associated Hemolytic Anemia in an Infant Born to a Mother with Lupus

A 31-day-old infant was admitted to the pediatric intensive care unit due to shock and anemia. The mother had systemic lupus erythematosus and direct antiglobulin test (DAT)-positive hemolytic anemia. The perinatal course of this infant and the mother was uneventful. Regular health check screenings revealed that activity, growth, and development were unremarkable at birth, 5, and 28 days of life. Passive immune hemolytic anemia due to neonatal lupus erythematosus was diagnosed based on a positive DAT for warm-type IgG antibodies, reticulocytosis, and lupus-specific antibodies at rehospitalization. It was complicated by cytomegalovirus (CMV) antigenemia. Umbilical cord blood and peripheral blood samples obtained from the infant at 5 days after birth were negative for CMV DNA. The infant was curatively treated by intensive care with repeated blood transfusions and antiviral therapy. This is the first report indicating that CMV infection exacerbates hemolytic anemia in patients with maternal red blood cell alloantibodies.

Developmental outcome of very low birth weight twins conceived by assisted reproduction techniques

OBJECTIVE

To evaluate the differences in developmental outcomes between very low birth weight twins conceived by assisted reproduction techniques and those conceived spontaneously.

STUDY DESIGN

Twenty-two sets of very low birth weight twins were evaluated by the Kyoto Scale for Psychological Development at 36 months of corrected age. Total developmental quotient and developmental quotient (DQ) for three subscales, posture-motor, cognition-adaptation and language-social, were evaluated.

RESULTS

Twins conceived with medical assistance demonstrated a higher incidence of total DQ below 85 with lower DQ for cognition-adaptation and language-social skills than spontaneously conceived twins, whereas the quotient for posture-motor skills in medically assisted twins was comparable to that of spontaneously conceived twins.

CONCLUSION

At 3 years of age very low birth weight twins conceived by assisted reproduction techniques demonstrated lower cognitive and language skills than twins conceived naturally.

A spontaneous mouse mutation, mesenchymal dysplasia (mes), is caused by a deletion of the most C-terminal cytoplasmic domain of patched (ptc)

A recessive mouse mutation, mesenchymal dysplasia (mes), which arose spontaneously on Chromosome 13, causes excess skin, increased body weight, and mild preaxial polydactyly. Fine gene mapping in this study indicated that mes is tightly linked to patched (ptc) that encodes a transmembrane receptor protein for Shh. Molecular characterization of the ptc gene of the mes mutant and an allelism test using a ptc knockout allele (ptc(-)) demonstrated that mes is caused by a deletion of the most C-terminal cytoplasmic domain of the ptc gene. Since mes homozygous embryos exhibit normal spinal cord development as compared with ptc(-) homozygotes, which die around 10 dpc with severe neural tube defects, the C-terminal cytoplasmic domain lost in mes mutation is dispensable for inhibition of Shh signaling in early embryogenesis. However, compound heterozygotes of ptc(-) and mes alleles, which survive up to birth and die neonatally, had increased body weight and exhibited abnormal anteroposterior axis formation of the limb buds. These findings indicate that Ptc is a negative regulator of body weight and ectopic activation of Shh signaling in the anterior mesenchyme of the limb buds, and that the C-terminal cytoplasmic domain of Ptc is involved in its repressive action.

Sphingosylphosphorylcholine is an activator of transglutaminase activity in human keratinocytes

We characterize functional roles of a newly discovered chemical, sphingosylphosphorylcholine (SPC), in the epidermis by elucidating the biological effect of SPC on human keratinocytes in culture. The intracellular calcium level of human keratinocytes was increased by incubation with SPC, but not with sphingosine (SS) or sphingomyelin (SM). The addition of SPC, sphingosine 1-phosphate (SSP), or SS to human keratinocytes at 10 microM concentrations also significantly suppressed DNA synthesis, and SPC, but not SSP, or SS increased the activities of membrane-bound and soluble transglutaminases (TGases). Reverse transcription polymerase chain reaction (RT-PCR) of TGase transcripts revealed that SPC treatment at 10 microM concentrations increased the expression of TGase 1 mRNA. The increased activity of soluble TGase was accompanied by the concomitant activation of cathepsin D as revealed by the increased ratio of mature active form to inactive intermediate form of the protease. Pretreatment of human keratinocytes with pepstatin, a protease inhibitor, blocked the increase in soluble TGase activity induced by treatment with SPC. Consistently, SPC treatment at 1-10 microM concentrations stimulated the cornified envelope formation. These findings suggest that SPC plays an important role in the altered keratinization process of epidermis in skin diseases with high expression of sphingomyelin deacylase, such as atopic dermatitis.

Development of a new instrument to measure oxygen saturation and total hemoglobin volume in local skin by near-infrared spectroscopy and its clinical application

The oxygen saturation (StO2) and total hemoglobin volume in cutaneous blood are closely related to cutaneous metabolism and are important factors in determining the skin color. Most conventional apparatuses for the measurement of cutaneous metabolism have been designed to evaluate qualitative changes in the oxyhemoglobin volume, deoxyhemoglobin volume, and their sum (total Hb volume) relative to their baseline values. In this study, we developed an instrument for non-invasive evaluation of individual and regional differences in StO2 and Hb volume, a system unaffected by melanin (Kao PSA system model III), and examined the validity of its application. First, changes in StO2 and total Hb volume in the antebrachial region during venous occlusion and devascularization by compression of the brachial region were evaluated. Changes in total Hb volume following venous occlusion were found to reflect the cutaneous blood flow. Also, StO2 was considered to reflect the state of oxygen consumption by the skin, because it was markedly reduced during devascularization. Next, the subjects were exposed to graded hypobaric conditions, and the relationships among StO2, arterial blood oxygen saturation (SaO2), and venous blood oxygen saturation (SvO2) were studied. StO2 showed significant positive correlations with SaO2 (r=0.811, P<0.001) and SvO2 (r=0.966, P<0.001), and its correlation with SvO2 was particularly strong. Therefore, StO2 was found to be closely dependent on SvO2. Lastly, StO2, total Hb volume, and other parameters were measured in healthy women (aged 20-69 years), and their regional differences and age-associated changes were evaluated. These regional differences (angle of mouth > cheek > forehead) and age-associated decreases in StO2 are considered to be caused by the age-associated decreases in the cutaneous blood flow.

Sphingosylphosphorylcholine is a potent inducer of intercellular adhesion molecule-1 expression in human keratinocytes

We recently reported that the epidermis of patients with atopic dermatitis contains an abnormally expressed sphingomyelin deacylase that yields a large amount of sphingosylphosphorylcholine (SPC) rather than ceramide. In this study, we characterize inflammatory roles of newly discovered chemicals in the epidermis by elucidating biologic effects of SPC on intercellular adhesion molecules-1 (ICAM-I) expression by human keratinocytes in culture in comparison with other sphingolipids. Using fluorescence-activated cell sorter analysis, we found that SPC treatment at concentrations of 10-20 microM significantly enhanced the expression of ICAM-I by cultured human keratinocytes in a dose-dependent manner after incubation for 15-24 h, and, using northern blot analysis, that this was accompanied by increased expression of ICAM-1 mRNA within 4 h of incubation. Transforming necrosis factor-alpha (TNF-alpha) levels in the medium of keratinocytes treated at a 10 microM concentration of SPC were significantly increased by 200%. Furthermore, the SPC-induced ICAM-1 expression was partially abolished by the concomitant addition of anti-TNF-alpha, suggesting a partial autocrine involvement of TNF-alpha in ICAM-1 expression. Assay of mitogen-activated protein kinase revealed that 10 microM SPC induced a rapid activation of mitogen-activated protein kinase in human keratinocytes, including an increase in its phosphorylation within 5 min, which then declined to the baseline control level after 30 min. In contrast, sphingomyelin or sphingosine had no significant potential to activate mitogen-activated protein kinase at the same concentration. These findings suggest that SPC plays an important role in the inflammatory process of epidermis in skin diseases, such as atopic dermatitis, with high expression of sphingomyelin deacylase.

Biological characterization of human fibroblast-derived mitogenic factors for human melanocytes

To clarify the paracrine linkage between human fibroblasts and melanocytes in cutaneous pigmentation, we studied the effects of human fibroblast-derived factors on the proliferation of human melanocytes. In medium conditioned for 4 days with human fibroblast culture, factors were produced that markedly stimulated DNA synthesis of human melanocytes. The stimulatory effect was higher in medium conditioned with fibroblasts from aged skin than in medium conditioned with fibroblasts from young skin, and was interrupted by inhibitors of tyrosine kinase, such as tyrphostin, genistein and herbimycin, but not by inhibitors of protein kinases C and A, such as H-7 and phloretin. The conditioned medium was also capable of activating mitogen-activated protein kinase of human melanocytes, with old fibroblasts being more effective than young ones. Analysis of factors released into the conditioned medium revealed that levels of hepatocyte growth factor (HGF) and stem cell factor (SCF) were increased in old-fibroblast-conditioned medium compared with young-fibroblast-conditioned medium. In contrast, levels of basic fibroblast growth factor (bFGF) were similar in both media. When the conditioned medium was treated with HGF antibody with or without SCF antibody, the increase in DNA synthesis by human melanocytes was decreased to 20% of the elevated level, whereas antibodies to bFGF had no effect. Analysis of the medium conditioned for 4 days after cytokine application demonstrated that, of the cytokines tested, interleukin 1alpha and tumour necrosis factor alpha are highly effective in stimulating HGF secretion by old fibroblasts. HGF and SCF, but not bFGF, were markedly increased in culture medium in the presence of IL-1alpha, and this stimulatory effect was confined to young human fibroblasts. These findings suggest that SCF and HGF derived from human fibroblasts may play a part in regulating cutaneous pigmentation during inflammation and aging.

Purification and characterization of an allergy-induced melanogenic stimulating factor in brownish guinea pig skin

We have demonstrated recently that phenylazonaphthol (PAN) allergy-induced hyperpigmentation in brownish guinea pig skin is associated with the concomitant appearance of a melanogenic soluble factor(s) that activates the intracellular signal transduction system, including phosphatidylinositol turnover subsequent to ligand-receptor binding in cultured guinea pig melanocytes. In this study we have purified and characterized the PAN-induced melanogenic stimulating factor (PIMSF) that occurs in allergy-associated hyperpigmented skin. By successive column chromatography on TSK 2000SW, Mono Q, and octadecyl-NPR, the PIMSF was purified to homogeneity with a single band of apparent molecular mass of 7.9 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The specific bioactivity of PIMSF increased by 5,195-fold over the original skin homogenate. In cultured guinea pig melanocytes, this purified PIMSF had the potential of activating an intracellular signal transduction system such as inositol 1,4,5-trisphosphate formation and intracellular calcium levels through a pertussis toxin-sensitive G protein-coupled receptor. PIMSF consistently caused a rapid translocation of cytosolic protein kinase C (PKC) to membrane-bound PKC within 5 min of treatment with a return to the basal level after 120 min. The stimulating effects of PIMSF on proliferation and melanization of cultured guinea pig melanocytes were abolished completely by a PKC down-regulating agent (phorbol 12,13-dibutyrate). PIMSF was similar in molecular mass to rat growth-related oncogene alpha (GRO-alpha; molecular mass of 7.9 kDa) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and had immunocross-reactivity with GRO-alpha upon Western immune blotting analysis. Further, the stimulatory effect of purified PIMSF on DNA synthesis of cultured guinea pig melanocytes was suppressed markedly by the addition of anti-rat GRO-alpha antibody, implying that the PIMSF is apparently identical to GRO-alpha. These findings suggest that PAN allergy provides a new mechanism of hyperpigmentation in which biological factors such as the GRO-alpha superfamily generated within allergy-induced skin stimulate melanocytes through activation of the PKC-related signal transduction pathway.

The role of endothelin-1 in epidermal hyperpigmentation and signaling mechanisms of mitogenesis and melanogenesis

The paracrine linkage of endothelins (ET) between keratinocytes and melanocytes suggested that ETs are intrinsic mediators for human melanocytes in UVB-induced pigmentation. In this study, the role of ET-1 in the epidermal hyperpigmentation was investigated in vivo and in vitro. The addition of 10 nM ET-1 induced a H-7 (10 microM) suppressible-increase in tyrosinase activity in cultured human melanocytes and was accompanied by elevated levels of tyrosinase and tyrosinase-related protein-1 mRNA expression as shown by Northern blotting. Analysis of signaling mechanisms leading to tyrosinase activation demonstrated the involvements of quick translocation of PKC, the H-7 (10 microM) suppressible-phosphorylation of the threonine residue of several proteins, and highly elevated level of cyclic AMP (4-fold over control). Reverse transcription polymerase chain reaction (RT-PCR) of RNA isolated from the epidermis of human skin exposed to UVB revealed that UVB irradiation with a dose of 2 MED caused a significant increase in the expressions of ET-1, IL-1 alpha, and tyrosinase mRNA signals 5 days after irradiation. The involvement of ET-1 in UVB-pigmentation was also corroborated by the experiments that the extracts of M. Chamomilla, which can act as an antagonist for ET-receptor binding-mediated signaling but has no inhibitory effect on tyrosinase activity in culture, had a significant inhibitory effect on UVB-induced pigmentation in vivo when daily applied immediately after UVB exposure to human skin. These findings suggest that ET-1 is an important mediator in the epidermis for UVB-induced pigmentation in vivo.

Abnormal expression of sphingomyelin acylase in atopic dermatitis: an etiologic factor for ceramide deficiency?

Previously, we demonstrated that there is a marked reduction in the amount of ceramide in the stratum corneum of both lesional and nonlesional forearms in atopic dermatitis (AD), suggesting that an insufficiency of ceramides in the stratum corneum is an etiologic factor in atopic dry and barrier-disrupted skin. In this study, we investigated, as a possible mechanism involved in the ceramide deficiency, whether sphingomyelin (SM) metabolism is altered in AD as compared to normal controls. In stripped stratum corneum and biopsied whole epidermis of patients with AD, SM hydrolysis as measured at pH 4.7 using [choline-methyl-14C]sphingomyelin as a substrate were markedly increased by 27- and 7-fold, respectively. Radio-thin-layer chromatography of the reaction products revealed that, whereas the SM hydrolysis in age-matched normal controls were associated with sphingomyelinase (SMase) that degrades SM to yield ceramides and phosphorylcholine (PC), most of the SM hydrolysis detected in AD were attributable not to the SMase but to a hitherto undiscovered epidermal enzyme, SM acylase, which releases free fatty acid and sphingosyl-PC (Sph-PC) instead of ceramides. The potential of this acylase-like enzyme to generate Sph-PC through SM hydrolysis was corroborated by thin-layer chromatographic analysis of the reaction products obtained using porcine kidney acylase, followed by high-performance liquid chromatography-mass spectrometry. Furthermore, Sph-PC was also detected by high-performance liquid chromatography-mass spectrometry after incubation of SM with atopic stratum corneum samples. On the other hand, the stratum corneum of patients with contact dermatitis or chronic eczema exhibited neither increased SM hydrolysis nor the generation of Sph-PC upon radio-thin-layer chromatographic analysis. These findings suggest that SM metabolism is altered in AD, resulting in a decrease in levels of ceramides, which could be an etiologic factor in the continuous generation of atopic dry and barrier disrupted skin observed in AD.

Signalling mechanisms of endothelin-induced mitogenesis and melanogenesis in human melanocytes

To understand the signalling mechanisms involved in the dual stimulatory effects of endothelin-1 (ET-1) on DNA synthesis and melanization in cultured human melanocytes, we analysed the biological profile of ET-1 receptor and determined the effects of ET-1 on the protein kinase C, cyclic AMP system and mitogen-activated protein kinase (MAP kinase) in comparison with their relevant stimulants. The photoaffinity labelling of ET-1 receptors with Denny-Jaff reagents revealed an ET-1 receptor with a molecular mass of 51 kDa in human melanocytes. The ET(A) receptor subtype-sensitive antagonist BQ123(50 nM) or pertussis toxin (100 ng/ml) significantly suppressed the ET-1-induced intracellular calcium mobilization, indicating the presence of pertussis toxin-sensitive G-protein-coupled ET(A) receptors. An assay of protein kinase C activity revealed that 10nM ET-1 translocated cytosolic protein kinase C to membrane-bound protein kinase C within 5 min of the start of incubation. In contrast, receptor-mediated melanocyte activation by ET-1 was accompanied by an elevated level of cyclic AMP (4-fold over control) after 10-60 min of incubation, whereas 60 min of incubation of human melanocytes with c-Kit or c-Met ligands such as stem cell factor (10 nM) or basic fibroblast growth factor (10 nM) did not elevate the cyclic AMP level. We have also demonstrated that a specific tyrosine kinase inhibitor, tyrphostin B-42 (10 microM), inhibited the ET-1-induced growth stimulation, suggesting the involvement of the tyrosine kinase pathway in growth stimulation. Consistently, an assay of MAP kinase revealed that ET-1 caused a 10-fold activation of MAP kinase after 5 min of incubation with human melanocytes in a similar way to tyrosine kinase ligands such as stem cell factor and hepatocyte growth factor. Further, the DNA synthesis stimulated by the c-Kit ligand stem cell factor at a concentration of 1 nM was synergistically enhanced by 5 nM ET-1. These results suggest that ET-induced dual cellular events in human melanocytes are closely associated with cross-talk between the protein kinase C and A and tyrosine kinase pathways.

Granulocyte/macrophage colony-stimulating factor is an intrinsic keratinocyte-derived growth factor for human melanocytes in UVA-induced melanosis

Recently we demonstrated that endothelins secreted from human keratinocytes act as intrinsic mitogens and melanogens for human melanocytes in UVB-induced melanosis. We show here that UVA-induced melanosis is associated with other keratinocyte-derived growth factors, secretion of which is specifically stimulated after exposure of human keratinocytes to UVA. Medium conditioned by UVA-exposed human keratinocytes elicited a significant increase in DNA synthesis by cultured human melanocytes in a UVA dose-dependent manner. Analysis of endothelin-1 and interleukin (IL)-1 alpha in the conditioned medium by ELISA, both of which are major keratinocyte-derived cytokines involved in UVB-associated melanocyte activation, revealed that UVA exposure did not cause human keratinocytes to stimulate the secretion of the two cytokines. In contrast, the levels of several other cytokines such as IL-6, IL-8 and granulocyte/macrophage colony-stimulating factor (GM-CSF) were significantly increased in the conditioned medium of human keratinocytes after exposure to UVA at a dose of 1.0 J/cm2. The gel chromatographic profile of UVA-exposed keratinocyte-conditioned medium demonstrated that there were two factors (P-1 and P-2) with molecular masses of approx. 20 and 1 kDa respectively that stimulate DNA synthesis in human melanocytes, and the larger species (P-1) also increased melanization as assessed by [14C]thiouracil incorporation. Quantitative analysis of cytokines in chromatographic fractions by ELISA revealed the P-1 fraction to be consistent with the molecular mass profile of GM-CSF. Furthermore the stimulatory effect of the P-1 fraction on DNA synthesis in human melanocytes was neutralized by antibodies to GM-CSF, but not to basic fibroblast growth factor or stem cell factor. Binding and proliferation assays with recombinant GM-CSF demonstrated that human melanocytes possess specific binding sites for GM-CSF(Kd 2.11 nM; binding sites, 2.5-3.5 x 10(4) per cell), and recombinant GM-CSF at concentrations of more than 10 nM significantly stimulated DNA synthesis and melanization. These findings suggest that GM-CSF secreted by keratinocytes plays an essential role in the maintenance of melanocyte proliferation and UVA-induced pigmentation in the epidermis.

High thoracic neurinoma mimicking femoral neuralgia

We report a case of spinal neurinoma at a high thoracic level, whose main presentation was intractable pain in a body part innervated by the right femoral nerve. Sensations of pain and temperature were impaired in the right thigh, but usual symptoms of myelopathy were undetectable. In conjunction with the other reports, this case suggests that spinal tumors at high thoracic levels can produce remote symptoms mimicking peripheral neuropathy such as femoral or sciatic neuralgia.

Endothelin-1 as a new melanogen: coordinated expression of its gene and the tyrosinase gene in UVB-exposed human epidermis

We previously demonstrated that human keratinocytes produce and secrete endothelins (ET), which can be strong mitogens for human melanocytes. Ultraviolet B (UVB) exposure highly stimulated the paracrine linkage of endothelins between keratinocytes and melanocytes, indicating that they are keratinocyte-derived intrinsic mitogens in UVB-induced pigmentation. In this study, the role of ET-1 as a melanogen in UVB melanogenesis was investigated in vitro and in vivo. In the conditioned medium of keratinocytes exposed to UVB, melanin synthesis by human melanocytes, as measured by 14C-thiouracil incorporation, was significantly accentuated. This stimulatory effect was reduced by anti-ET-1 to the level of that in the non-UVB-exposed control, suggesting an essential role of ET-1 as an intrinsic melanogen in UVB-induced melanogenesis. In a parallel study, the addition of 10 nM ET-1 induced an increase in tyrosinase activity in cultured human melanocytes and was accompanied by elevated levels of tyrosinase and tyrosinase-related protein-1 mRNA expression as shown by Northern blotting. Reverse transcription-polymerase chain reaction of RNA isolated from the epidermis of human skin exposed to UVB revealed that, whereas in non-exposed sites ET-1, IL-1 alpha, and tyrosinase mRNA signals were scarcely detected, UVB-irradiation, with a dose of twice the minimal erythema dose, caused a significant increase in the expressions of the three genes 5 d after irradiation. These findings suggest that ET-1 is an important mediator for UVB-induced pigmentation in the epidermis in vivo.

Purification and biochemical characterization of membrane-bound epidermal ceramidases from guinea pig skin

Ceramidase (CDase) catalyzes the hydrolysis of ceramides to yield sphingosine and fatty acid. In this paper, two forms of membrane-bound alkaline ceramidase, have been, for the first time, purified from guinea pig epidermis by chromatography on DEAE-cellulose, phenyl-Superose, HCA-hyroxyapatite, isoelectric focusing, Mono Q, and TSK-3000SW column. One species (CDase-I) migrated upon SDS-polyacrylamide gel electrophoresis as a single band with an apparent molecular mass of 60 kDa; the other (CDase-II) was only partially purified with apparent M(r) of about 148,000 estimated by gel filtration. The specific activities of the two species increased by 1.130- (for CDase-I) and 400-fold (for CDase-II) over the original tissue extract. The activity of both enzymes for ceramide species decreased in the order of linoleoyl > oleoyl > palmitoylsphingosine. The optimal pH for enzyme activity was approximately 7.0-9.0 for CDase-I and 7.5-8.5 for CDase-II. Interestingly, both enzymes were inhibited by the reaction product sphingosine with a concentration for half-maximal inhibition (ID50) of 100-130 microM, compared to the apparent kinetic parameters with CDase-I (Km = 90 microM, Vmax = 0.62 unit) and CDase-II (Km = 140 microM, Vmax = 0.50 units). Some lipids, such as phosphatidylcholine and sphingomyelin, are also inhibitory with IC50 values of 50-250 microM, suggesting well controlled CDase activity by sphingolipid metabolites. These studies begin to elucidate a regulatory mechanism for the balance of the ratio of ceramide/sphingosine which can serve as an intracellular effector molecule in epidermis.

Analysis of beta-glucocerebrosidase and ceramidase activities in atopic and aged dry skin

To elucidate the mechanisms that are involved in the decrease of ceramide levels in atopic dry skin and in aged skin, we examined both the activities of beta-glucocerebrosidase, which is a major enzyme in ceramide production, and of ceramidase, which is an essential enzyme in ceramide degradation, in the stratum corneum of atopic dry skin and aged skin. The specimens of the stratum corneum of forearm skin were obtained by tape-stripping from 61 healthy volunteers and 23 patients with atopic uninvolved skin. The beta-glucocerebrosidase activity in the stratum corneum extracts was estimated using fluorescent 4-methylumbelliferyl-beta-D-glucopyranoside as the substrate. Ceramidase activity was determined using 14C-palmitoylsphingosine as the substrate. Among the atopic skin samples, neither beta-glucocerebrosidase nor ceramidase activities were different from those of age-matched healthy controls. Nor was the beta-glucocerebrosidase activity deficient in the aged skin samples as compared to that seen in samples from the young, healthy group. In contrast, there was an age-related upregulation in ceramidase activity. The results indicate that the decrease of ceramides in atopic dry skin may not be accompanied by reduced synthesis or by enhanced degradation, each of which is primarily attributable to the above two enzymes, respectively. The pathogenesis of aged dry skin can be explained, at least partially, in terms of elevated ceramidase activity, which results in a disturbance of the lamellar structure of the stratum corneum lipids.

[Survival of patients with gastric cancer treated with intra-lymph nodal injection of activated carbon particles absorbed mitomycin C]

We studied the efficacy of the intra-lymph nodal injection of the activated carbon particle absorbed mitomycin C (MMC-CH40) for gastric cancer. Ninety-five patients with gastric cancer underwent gastrectomy with D1 or D2 lymph node dissection. Of these, 38 patients were treated with intra-lymph nodal injection of MMC-CH 40 (MMC-CH 40 group). The other 57 patients were classified into the control group. The survival of MMC-CH group was significantly higher than that of the control group using generalized Wilcoxon method. However, since the percentage of stage IV was higher in the control group than in MMC-CH 40 group, the survivals of subgroups of stage I-III were compared. Although the percentage of the early gastric cancer was higher in the control group of stage I-III (n = 35) than in the MMC-CH group of stage I-III (n = 38), the survival curves of MMC-CH group were higher than in the control group. The difference in survival between the two groups was significant at 8 months after surgery. These results indicate that this new therapy improves survival in patients with stage I-III gastric cancer.

Pseudo-acylceramide with linoleic acid produces selective recovery of diminished cutaneous barrier function in essential fatty acid-deficient rats and has an inhibitory effect on epidermal hyperplasia

Pseudo-acylceramides with different acyl properties were investigated for their capacity to restore diminished barrier function in essential fatty acid-deficient rats. Daily topical applications of synthetic pseudo-acylceramides containing ester-linked linoleic acid caused a dose-dependent, significant reduction of transepidermal water loss (TEWL). Both other pseudo-acylceramides with ester-linked oleic acid or saturated alkyl chains and ordinary ceramides exhibited a poor effect on recovery of TEWL. Furthermore, pseudoceramide containing ether-linked linoleic acid, which is biologically inactive in terms of degradation by hydrolytic enzymes, also induced a significant and similar increase in the barrier function. This restoration of barrier function by pseudo-acylceramides with linoleic acid was accompanied by suppressed DNA synthesis in the EFAD rat epidermis. In UVB-irradiated guinea pig skin, topical applications of the pseudo-acylceramides with linoleic acid immediately after the exposure significantly reduced epidermal hyperplasia, secondary to markedly diminished barrier disruption, whereas linoleic acid itself did not. A comparison of both the anti-hyperplasia and the barrier recovery effects in the series of pseudo-ceramide derivatives examined revealed that the suppressive effect on the induced epidermal hyperplasia was paralleled by the recovery of the barrier defect in EFAD rats. These findings directly suggest that acylceramide with an ester-linked linoleic acid has an essential role in the epidermal permeability barrier.

[A severe case of reexpansion pulmonary edema in an asthmatic patient]

A 60-year-old man with poorly controlled bronchial asthma was proposed for an emergency appendectomy. His preoperative chest X-P revealed that his left lung was completely collapsed with pneumothorax, but its onset was unclear. Following the left thoracocentesis, appendectomy was performed under general anesthesia (oxygen-halothane). About one hour after the thoracocentesis, pinkish foamy tracheal secretion was massively drained and its protein concentration was 3.8 g.dl-1.PaCO2 was 95 mmHg and PaO2 was 69 mmHg (FIO2 1.0). His chest X-P showed signs of pulmonary edema in his left lung and infiltrating shadow was observed in his right lung. IMV with PEEP, aminophylline and prednisolone improved his respiratory status and on the 11 th day he was weaned from the respirator. In a case of pneumothorax with unclear duration like ours, it is necessary to consider the possibility of the reexpansion pulmonary edema.

Protein kinase C-dependent expression of type I transglutaminase mRNA in ganglioside GQ1b- and calcium-stimulated human keratinocytes

Ganglioside GQ1b was found to induce terminal differentiation in normal epidermal keratinocytes (Yada et al. (1991) Biochem. J. 279, 665-670). In GQ1b-stimulated human keratinocytes, the increase in mRNA expression of Type I TGase preceded the increases in the TGase activity. The enhancement of its mRNA expression was inhibited when protein kinase C (PKC) was suppressed by pretreatment with an inhibitor, H-7, or down-regulation by long-term preincubation with phorbol dibutyrate. These results indicate that PKC is involved in the activation of TGase probably via gene expression of TGase mRNA in GQ1b-induced human keratinocyte differentiation. Similar results were also obtained in Ca(2+)-induced differentiation.

Endothelins secreted from human keratinocytes are intrinsic mitogens for human melanocytes

We recently demonstrated that human melanocyte proliferation and differentiation could be stimulated by endothelin (ET) derivatives via a receptor-mediated signal transduction pathway (Yada, Y., Higuchi, K., and Imokawa, G. (1991) J. Biol. Chem. 266, 18352-18357). We show here that the growth factors for human melanocytes are produced and secreted by the surrounding cells, namely human keratinocytes for ET-1 and Big-ET-1. Northern blots have revealed the presence of ET-1 gene transcripts in proliferating human keratinocytes. The ET-1 production by human keratinocytes increased after irradiation with ultraviolet B (UVB) in a dose-dependent manner, accompanied by the significant secretion of interleukin 1 alpha (IL-1 alpha). Among the cytokines related to UVB-induced cellular reactions and keratinocyte growth, only IL-1 alpha and -1 beta stimulated the secretion of ET-1 and Big-ET-1 but not of ET-3 and Big-ET-3 in a time-dependent manner. Northern blots for IL-1 alpha-stimulated or UVB-exposed human keratinocytes revealed that production of ET-1 gene transcripts markedly increased (by about 300 or 1,200%) with constant levels of beta-actin gene transcripts. In a parallel study, the medium conditioned by UVB-exposed human keratinocytes elicited a significant anti-ET-1 antibody-suppressible increase in DNA synthesis by cultured human melanocytes in a UV dose-dependent manner, which was associated with a marked and rapid (80 s) increase in the intracellular calcium level upon incubation with human melanocytes. These studies suggest that ETs produced and secreted by keratinocytes play an essential role in the maintenance of melanocyte proliferation and UV hyperpigmentation in the epidermis.

Allergic contact dermatitis releases soluble factors that stimulate melanogenesis through activation of protein kinase C-related signal-transduction pathway

Phenylazo-naphthol (PAN) allergy induces visibly well-defined and late-appearing hyperpigmentation of brownish yellow guinea pig skin in clear contrast to dinitrochlorobenzene (DNCB) allergy, which has very low incidence of hyperpigmentation. Skin extract from PAN allergy at 20-29 d post-challenge exhibited marked melanogenic stimulatory effects (3H2O release and 14C-thiouracil incorporation) when added to cultured guinea pig melanocytes. The time course in the appearance of melanogenic factor was definitely consistent with the induction pattern of visible pigmentation. By contrast, the addition of DNCB-challenged skin extract demonstrated no significant stimulating effect on melanogenesis in either assay system on any of the post-challenge days tested. Assay of intracellular inositol 1,4,5-trisphosphate formed through incubation with the melanocytes demonstrated that the PAN-allergy skin extract at day 28, which contains definite melanogenic factors, stimulated the formation of inositol 1,4,5-trisphosphate that occurs around 50 seconds in contrast to no or little increase with extracts obtained at days 0 and 1 post-challenge. Gel chromatographic analysis revealed that the PAN-allergy skin extract at day 28 contained a newly generated melanogenic fraction with a molecular weight of approximately 9000 Da which was also capable of stimulating DNA synthesis and activating the signal-transduction process (inositol trisphosphate formation) when added to guinea pig melanocytes. Both stimulations of melanogenesis and DNA synthesis by the 9000 Da fraction were completely abolished by the prior and simultaneous addition of protein kinase C (PKC) inhibitor (H-7) or its down-regulatory agent, phorbol 12,13-dibutyrate (PdBu). Taken together, these results suggest that PAN allergy provides a new mechanism of hypermelanization in which endogenous factors synthesized within skin induce the activation of signal-transduction pathways such as phosphoinositide turnover through ligands-receptor binding, resulting in the stimulation of melanocytes possibly through the activation of PKC.

Ganglioside GQ1b-induced terminal differentiation in cultured mouse keratinocytes. Phosphoinositide turnover forms the onset signal

Investigations were undertaken to see whether mouse keratinocyte differentiation was elicited by gangliosides. Among the gangliosides tested only GQ1b, a tetrasialoganglioside containing two disialosyl residues, induced keratinocyte differentiation, as indicated by the formation of cornified envelopes, enhancement of transglutaminase activity and suppression of DNA synthesis. Upon stimulation with GQ1b the mass content of Ins(1,4,5)P3 and the intracellular Ca2+ levels were markedly enhanced in a time- and dose-dependent manner, whereas no significant changes were observed with other gangliosides, thereby indicating activation of phospholipase C for the onset of keratinocyte differentiation. Furthermore, only GQ1b promoted the translocation of protein kinase C (PKC) from cytosol to membrane. Inhibition of PKC with H-7 or down-regulation of the enzyme by prolonged pre-treatment with phorbol 12,13-dibutyrate greatly suppressed transglutaminase activity and formation of cornified envelopes induced by GQ1b. These results demonstrate that the tetrasialoganglioside GQ1b generates the initial differentiation signal in mouse keratinocytes through phosphoinositide turnover, and also suggest that PKC activation may act at certain, as yet unidentified, stages of differentiation processes.

Effects of endothelins on signal transduction and proliferation in human melanocytes

We demonstrate here that human melanocytes could be regulated by endothelin (ET) derivatives, potent vasoconstrictive peptides synthesized by endothelial cells, to stimulate their proliferation and melanization via a receptor-mediated signal transduction pathway. Receptor-binding assay using [125I]ET indicated that unlabeled ET-1 or ET-2 competitively inhibited each binding of labeled ETs to melanocytes with a concentration for half-maximal inhibition (IC50) of 0.7 or 0.9 nM, respectively. The dissociation constant (Kd) and the number of sites of the specific bindings of ET-1 and those of ET-2 were almost the same (Kd: 1.81 nM, binding sites: 7.0-8.0 x 10(4) per cell). Upon incubation with cultured cells, the mass contents of inositol 1,4,5-trisphosphate and intracellular calcium level were substantially increased by 10 nM ET-1, ET-2, and ET-3, but not by big-ET with maximal response at 80-130-s postincubation. The addition of ET-1 and ET-2 at 1-50 nM concentrations caused human melanocytes to significantly stimulate DNA [( 3H]thymidine incorporation) and melanin synthesis (3H2O release and [14C] thiouracil incorporation). Furthermore, ETs exhibited an additive stimulatory effect on basic fibroblast growth factor-stimulated DNA synthesis. In a long-term serum-free culture system, the strongest stimulation of growth by 10 nM ET-1 or ET-2 was observed in the presence of 10 nM cholera toxin and 0.2% bovine pituitary extract, resulting in a 4.5-fold increase in cell number for 12 culture days. These findings strongly suggest involvement of ET in the mechanism regulating proliferation and melanization of human melanocytes.

Purification and characterization of cytosolic diacylglycerol kinases of human platelets

Three isozymes of diacylglycerol kinase (DGK), DGK-I, DGK-II, and DGK-III, were purified from the cytosol of human platelets by successive chromatography on DEAE-cellulose, Ultrogel AcA34, heparin-Sepharose, ATP-agarose, Mono Q, phenyl-Superose, HCA-hydroxyapatite, Wakopak G40, and TSK-3000SW columns. Two DGK species (DGK-I and DGK-III) were purified to apparent homogeneity, and upon SDS-polyacrylamide gel electrophoresis, they showed a single band of apparent molecular mass of 152 kDa (DGK-I) or 58 kDa (DGK-III). The peptide mapping analysis showed that DGK-I and DGK-III are structurally different. DGK-II was only partially purified, and its apparent Mr was estimated to be 75,000 by gel filtration. The specific enzyme activities of the three isozymes were increased 1,480-fold (DGK-I), 690-fold (DGK-II) and 2,100-fold (DGK-III) over original platelet cytosol. The activities of DGK-II and DGK-III were markedly enhanced by the presence of deoxycholate or phosphatidylserine, whereas DGK-I activity was not much affected by the anionic compounds. All of the three activities were strongly suppressed by phosphatidylcholine. Triton X-100 and octyl glucoside were strongly inhibitory to all of the enzymes, although to different extents. The DGK inhibitor, R59022, inhibited DGK-II and to a lesser extent DGK-III, but little affected DGK-I activity. DGK-I was much more heat-stable than DGK-II and DGK-III. The Km values for ATP were 150 microM for DGK-I, 245 microM for DGK-II, and 450 microM for DGK-III. The apparent Km values for suspended diolein were not much different among the DGKs and were in the range of 50-80 microM. These observations indicate that human platelet cytosol contains DGK isozymes with different enzymological properties. Furthermore, the three DGKs isolated from human platelets were found not to cross-react with the antibody raised against porcine brain 80-kDa DGK, thus indicating that human platelets contain novel species of DGK.

Enhancement of GTP gamma S-binding activity by cAMP-dependent phosphorylation of a filamin-like 250 kDa membrane protein in human platelets

The treatment of human platelets with the dibutyryl cyclic AMP (dbcAMP) revealed the presence of a 250 kDa protein which enhanced its GTP-binding activity. This protein was purified from platelet membranes by successive chromatographies on DEAE-cellulose, Ultrogel AcA34, Mono Q, HCA-hydroxyapatite, and TSK-3000SW columns. The positive cross-reaction of the 250 kDa protein with the anti-filamin antibody indicated that this protein is filamin or very close to it. The GTP gamma S-binding activity of this protein, when phosphorylated with cyclic AMP-dependent protein kinase (A-kinase), showed an over tenfold increase, with the specific activity being 3.6 nmol/mg protein. Dephosphorylation of the phosphorylated protein with alkaline phosphatase reduced the GTP gamma S-binding activity to the control untreated level.

Bradykinin induces inositol 1,4,5-trisphosphate-dependent hyperpolarization in K+ M-current-deficient hybrid NL308 cells: comparison with NG108-15 neuroblastoma x glioma hybrid cells

External application of bradykinin (BK) to mouse neuroblastoma X mouse fibroblast hybrid NL308 cells and mouse neuroblastoma X rat glioma hybrid NG108-15 cells produced a transient outward (hyperpolarizing) current. In NG108-15 cells, BK also induced an inward (depolarizing) current associated with a decrease in input membrane conductance, which results from the inhibition of a voltage-sensitive potassium current, the M-current. However, in NL308 cells, either no depolarization was elicited by BK or, even if the BK-induced depolarization was evoked, it was associated with an increased conductance. To explain the above difference, the intracellular second messenger system of NL308 cells was examined in detail. BK induced the rapid accumulation (three- to fivefold higher than the control level) of inositol 1,4,5-trisphosphate (InsP3) in NL308 cells. The cytosolic Ca2+ concentration was also elevated to 540 nM from 180 nM at a basal level. This seems to be enough to activate a voltage-independent and Ca2(+)-sensitive K+ current, resulting in the hyperpolarization. Intracellular injection of InsP3 replicated the hyperpolarization. NL308 cells possess protein kinase C (C-kinase), with specific activities of C-kinase in cytosolic and membrane fractions being 233 and 24 pmol/min/mg protein, respectively. The activity associated with particulates became higher after phorbol dibutyrate (PDBu) treatment. But NL308 cells did not show the characteristic inward relaxation by step hyperpolarizations and the outward rectification in the current-voltage relationship, indicating that the M current is deficient in NL308 cells. Therefore, application of PDBu failed to mimic the inward current. The results suggest the role of InsP3 and C-kinase in controlling two K+ currents.

Signal transduction in the onset of terminal keratinocyte differentiation induced by 1 alpha,25-dihydroxyvitamin D3: role of protein kinase C translocation

We have investigated the possible involvement of phosphoinositide turnover in the keratinocyte differentiation induced by 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25(OH)2D3]. The mass contents of inositol 1,4,5-trisphosphate and 1,2-diacylglycerol and intracellular calcium level were measured in murine keratinocytes stimulated with 1 alpha,25(OH)2D3 or its derivatives. Although production of these second messengers was enhanced, there were no significant differences in time- and dose-dependences between 1 alpha,25(OH)2D3 and its derivatives. These vitamin D3 compounds promoted the translocation from the cytosol to membrane of protein kinase C (PKC). Despite such common profiles in the early signal transduction parameters, only 1 alpha,25(OH)2D3 induced formation of a cornified envelope characteristic of keratinocyte differentiation. Down-regulation of PKC by prolonged pretreatment with PDBu or inhibition of the enzyme with H-7 caused marked suppression of 1 alpha,25(OH)2D3-induced formation of cornified envelopes. These findings imply that PKC is necessary but not sufficient for the onset of terminal differentiation by 1 alpha,25(OH)2D3, and also that another as yet unspecified signal generated specifically by the active vitamin D3 is required for keratinocyte differentiation.

Inhibition by cyclic AMP of guanine nucleotide-induced activation of phosphoinositide-specific phospholipase C in human platelets

Phosphoinositide-specific phospholipase C (PLC) activity of human platelet membranes was activated by the nonhydrolyzable guanine nucleotide GTP gamma S. This activation did not occur in either membranes prepared from dibutyryl cyclic AMP-pretreated platelets (A-membranes) or those prepared from untreated cells and subsequently incubated with cyclic AMP (cAMP) (B-membranes). This cAMP-mediated inhibition was abolished in the presence of inhibitors of cAMP-dependent protein kinase (A-kinase), suggesting that the inhibition was due to phosphorylation of (a) protein component(s). No significant differences were observed in the basal PLC activity and the extent of pertussis toxin-catalyzed ADP-ribosylation among control membranes and the two types of phosphorylated membranes (A- and B-membranes). GTP-binding activities of Gs, Gi and GTP-binding proteins of lower molecular masses were not altered by the phosphorylation of the membranes. These findings suggest that a GTP-binding protein is involved in the GTP gamma S-mediated activation of PLC and that cAMP (plus A-kinase) inhibits this activation by phosphorylating a membrane protein (probably a 240-kDa protein), rather than the GTP-binding protein or PLC itself. It is likely that this phosphorylation uncouples the GTP-binding protein from PLC.

Phosphoinositide-specific phospholipase C of a cloned mast cell line, mastocytoma P-815: purification and some characterization

1. Multiple forms of phosphoinositide-phospholipase C (PLC) were isolated from mastocytoma; two cytosolic forms (cPLC-I, Mr 150,000; cPLC-II, Mr 110,000) and two membrane-associated forms (mPLC-I, Mr 85,000; mPLC-II, Mr 85,000). 2. Four PLC forms differently behaved in substrate specificity and effect of GTP-binding proteins.

Defective formation of inositol 1,4,5-trisphosphate in bradykinin-stimulated fibroblasts from progressive systemic sclerotic patients

The effect of bradykinin on inositol 1,4,5-trisphosphate (1,4,5-IP3) formation was investigated in fibroblasts from normal subjects and patients with progressive systemic sclerosis (PSS). 1,4,5-IP3 in both PSS and normal fibroblasts reached peak levels at 15 sec after stimulation with bradykinin, though this level was significantly lower in PSS fibroblasts than in normal cells. There was no difference in 1,4,5-IP3 content between islet-activating protein (IAP)-treated and untreated cells in either PSS or normal fibroblasts. These findings suggest that bradykinin stimulates phosphoinositide hydrolysis by phospholipase C in human fibroblasts via IAP-insensitive pathway, and that PSS fibroblasts appear to be defective in the pathway.

Purification and characterization of membrane-bound phospholipase C specific for phosphoinositides from human platelets

Two peaks (mPLC-I and mPLC-II) of phosphatidylinositol 4,5-bisphosphate (PIP2)-hydrolyzing activity were resolved when 1% sodium cholate extract from particulate fractions of human platelet was chromatographed on a heparin-Sepharose column. The major peak of enzyme activity (mPLC-II) was purified to homogeneity by a combination of Fast Q-Sepharose, heparin-Sepharose, Ultrogel AcA-44, Mono Q, Superose 6-12 combination column, and Superose 12 column chromatographies. The specific activity increased 2,700-fold as compared with that of the starting particulate fraction. The purified mPLC-II had an estimated molecular weight of 61,000 on sodium dodecyl sulfate-polyacrylamide gels. The minor peak of enzyme activity (mPLC-I) was partially purified to 430-fold. Both enzymes hydrolyzed PIP2 at low Ca2+ concentration (0.1-10 microM) and exhibited higher Vmax for PIP2 than for phosphatidylinositol. PIP2-hydrolyzing activities of both enzymes were enhanced by various detergents and lipids, such as deoxycholate, cholate, phosphatidylethanolamine, and dimyristoylphosphatidylcholine. The mPLC-I and mPLC-II activities were increased by Ca2+, but not by Mg2+, while Hg2+, Fe2+, Cu2+, and La3+ were inhibitory. GTP-binding proteins (Gi, Go, and Ki-ras protein) had no significant effects on the mPLC-II activity.

Induction of melanization within hair bulb melanocytes in chinchilla mutant by melanogenic stimulants

In an attempt to clarify the mechanisms underlying the lack of melanin formation in hair bulb melanocytes of chinchilla mice (genotype a/a, cch/cch, strain PW), we studied the effect of exogenous melanogenic stimulants such as theophylline (Tp), dibutyryl cyclic AMP (db-cAMP), and alpha-melanocyte-stimulating hormone (alpha-MSH) on the induction of melanization. Skin explants excised from the dorsa of chinchilla or lethal yellow C57BL/6J, Ay/a) mice at 7 to 9 days of age were cultured in the presence of Tp (2 mM), db-cAMP (2 mM), or alpha-MSH (1.0 microgram/ml). After 2 to 5 days, melanin formation was induced in hair bulb melanocytes of chinchilla mutant in response to both Tp and db-cAMP, but alpha-MSH did not produce new melanin formation. In contrast, yellow mutant increased the melanin formation in response to all stimulants. Electron microscopic studies demonstrated that while non-treated hair bulb melanocytes of chinchilla mutant contain a large number of stage II-III melanosomes without melanin deposition, a hair bulb treated with Tp exhibits the new formation of melanin within melanosomes that appears both as typical eumelanosomes with striated longitudinal matrices and as pheomelanosomes with vacuolar melanization. Quantitative analysis of melanin has revealed that in chinchilla mutant, Tp and db-cAMP induce a severalfold increase in the formation of both eumelanin [pyrrole-2,3,5-tricarboxylic acid (PTCA)] and pheomelanin (aminohydroxyphenylalanine), whereas alpha-MSH does not stimulate production of either melanin. In yellow mutant, db-cAMP induced a remarkable increase in eumelanin (PTCA), in contrast to the fewfold increase induced by alpha-MSH and Tp. All stimulants induced a slight increase in pheomelanin to a similar extent. These different reactions to melanogenic stimulation suggest a possible defect in the tyrosinase activation system within hair bulb melanocytes in chinchilla mutants.