Functionality of bone marrow mesenchymal stromal cells derived from head and neck cancer patients - A FDA-IND enabling study regarding MSC-based treatments for radiation-induced xerostomia

PURPOSE

Salivary dysfunction is a significant side effect of radiation therapy for head and neck cancer (HNC). Preliminary data suggests that mesenchymal stromal cells (MSCs) can improve salivary function. Whether MSCs from HNC patients who have completed chemoradiation are functionally similar to those from healthy patients is unknown. We performed a pilot clinical study to determine whether bone marrow-derived MSCs [MSC(M)] from HNC patients could be used for the treatment of RT-induced salivary dysfunction.

METHODS

An IRB-approved pilot clinical study was undertaken on HNC patients with xerostomia who had completed treatment two or more years prior. Patients underwent iliac crest bone marrow aspirate and MSC(M) were isolated and cultured. Culture-expanded MSC(M) were stimulated with IFNγ and cryopreserved prior to reanimation and profiling for functional markers by flow cytometry and ELISA. MSC(M) were additionally injected into mice with radiation-induced xerostomia and the changes in salivary gland histology and salivary production were examined.

RESULTS

A total of six subjects were enrolled. MSC(M) from all subjects were culture expanded to > 20 million cells in a median of 15.5 days (range 8-20 days). Flow cytometry confirmed that cultured cells from HNC patients were MSC(M). Functional flow cytometry demonstrated that these IFNγ-stimulated MSC(M) acquired an immunosuppressive phenotype. IFNγ-stimulated MSC(M) from HNC patients were found to express GDNF, WNT1, and R-spondin 1 as well as pro-angiogenesis and immunomodulatory cytokines. In mice, IFNγ-stimulated MSC(M) injection after radiation decreased the loss of acinar cells, decreased the formation of fibrosis, and increased salivary production.

CONCLUSIONS

MSC (M) from previously treated HNC patients can be expanded for auto-transplantation and are functionally active. Furthermore IFNγ-stimulated MSC(M) express proteins implicated in salivary gland regeneration. This study provides preliminary data supporting the feasibility of using autologous MSC(M) from HNC patients to treat RT-induced salivary dysfunction.

Ruxolitinib inhibits IFNγ-stimulated Sjögren's salivary gland MSC HLA-DR expression and chemokine-dependent T cell migration

OBJECTIVES

Sjögren's disease (SjD) is a systemic autoimmune disease characterized by focal lymphocytic infiltrate of salivary glands (SGs) and high SG IFNγ, both of which are associated with elevated lymphoma risk. IFNγ is also biologically relevant to mesenchymal stromal cells (MSCs), a SG resident cell with unique niche regenerative and immunoregulatory capacities. In contrast to the role of IFNγ in SjD, IFNγ promotes an anti-inflammatory MSC phenotype in other diseases. The objective of this study was to define the immunobiology of IFNγ-exposed SG-MSCs with and without the JAK1 & 2 inhibitor, ruxolitinib.

METHODS

SG-MSCs were isolated from SjD and controls human subjects. SG-MSCs were treated with 10 ng/ml IFNγ +/- 1000 nM ruxolitinib. Experimental methods included flow cytometry, RNA-sequencing, chemokine array, ELISA and transwell chemotaxis experiments.

RESULTS

We found that IFNγ promoted expression of SG-MSC immunomodulatory markers, including HLA-DR, and this expression was inhibited by ruxolitinib. We confirmed the differential expression of CXCL9, CXCL10, CXCL11, CCL2 and CCL7, initially identified with RNA sequencing. SG-MSCs promoted CD4+ T cell chemotaxis when pre-stimulated with IFNγ. Ruxolitinib blocks chemotaxis through inhibition of SG-MSC production of CXCL9, CXCL10 and CXCL11.

CONCLUSIONS

These findings establish that ruxolitinib inhibits IFNγ-induced expression of SG-MSC immunomodulatory markers and chemokines. Ruxolitinib also reverses IFNγ-induced CD4+ T cell chemotaxis, through inhibition of CXCL9, -10 and -11. Because IFNγ is higher in SjD than control SGs, we have identified SG-MSCs as a plausible pathogenic cell type in SjD. We provide proof of concept supporting further study of ruxolitinib to treat SjD.

Minor salivary gland mesenchymal stromal cells derived from patients with Sjӧgren's syndrome deploy intact immune plasticity

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) provide minor salivary glands (MSGs) with support and niche cells for epithelial glandular tissue. Little is known about resident MSG-derived MSCs (MSG-MSCs) in primary Sjӧgren's syndrome (PSS). The authors' objective is to define the immunobiology of endogenous PSS MSG-MSCs.

METHODS

Using culture-adapted MSG-MSCs isolated from consenting PSS subjects (n = 13), the authors performed in vitro interrogation of PSS MSG-MSC immunobiology and global gene expression compared with controls. To this end, the authors performed phenotypic and immune functional analysis of indoleamine 2,3-dioxygenase (IDO), programmed death ligand 1 (PD-L1) and intercellular adhesion marker 1 (ICAM-1) before and after interferon γ (IFNγ) licensing as well as the effect of MSG-MSCs on T-cell proliferation. Considering the female predominance of PSS, the authors also addressed the influence of 17-β-estradiol on estrogen receptor α-positive-related MSC function.

RESULTS

The authors found that MSG-MSCs deployed normal immune regulatory functionality after IFNγ stimulation, as demonstrated by increased protein-level expression of IDO, PD-L1 and ICAM-1. The authors also found that MSG-MSCs suppressed T-cell proliferation in a dose-dependent manner independent of 17-β-estradiol exposure. Gene ontology and pathway analysis highlighted extracellular matrix deposition as a possible difference between PSS and control MSG-MSCs. MSG-MSCs demonstrated increased α-smooth muscle actin expression in PSS, indicating a partial myofibroblast-like adaptation.

CONCLUSIONS

These findings establish similar immune regulatory function of MSG-MSCs in both PSS and control patients, precluding intrinsic MSC immune regulatory defects in PSS. PSS MSG-MSCs show a partial imprinted myofibroblast-like phenotype that may arise in the setting of chronic inflammation, providing a plausible etiology for PSS-related glandular fibrosis.

Washed Equine Platelet Extract as an Anti-Inflammatory Biologic Pharmaceutical

Mammalian platelets participate in the immediate tissue injury response by initiating coagulation and further promoting tissue injury mitigation and repair. The latter properties are deployed following platelet release of presynthetized morphogens, cytokines, and growth and chemotactic factors, which launch a tissue regenerative, angiogenic, and anti-inflammatory program. Several blood-derived biologic products, like platelet-rich plasma (PRP) and platelet lysate (PL), are currently on the market to allow proper healing and tissue regeneration. However, not all growth factors are released from the platelets and the final products contain plasma proteins such as albumin, fibrinogen, complement, and immunoglobulins, increasing the risks of serum sickness or allergic reaction. To address this problem, we developed a new platelet extract where equine blood platelets are concentrated, washed, and thereafter lysed by detergent Triton X-114. Distinct from PRP, this extract is devoid of albumin, fibrinogen, and immunoglobulins and is 266-fold enriched in platelet-derived growth factor content relative to PRP. Washed equine platelet extract (WEPLEX) is amenable to lyophilization without loss of biological activity. In vitro, WEPLEX significantly inhibits human and equine T cell proliferative response to phytohemagglutinin and also polarizes murine CD45⁺/CD11b⁺ peritoneal macrophages to an IL-10⁺ M2-like phenotype. In vivo, WEPLEX substantially improves clinical outcome of murine experimental dextran sulfate sodium colitis. We propose that equine-sourced, zoonosis-free WEPLEX may serve as an anti-inflammatory biological therapy across mammalian species.

A systems pharmacology-based approach to identify novel Kv1.3 channel-dependent mechanisms in microglial activation

BACKGROUND

Kv1.3 potassium channels regulate microglial functions and are overexpressed in neuroinflammatory diseases. Kv1.3 blockade may selectively inhibit pro-inflammatory microglia in neurological diseases but the molecular and cellular mechanisms regulated by Kv1.3 channels are poorly defined.

METHODS

We performed immunoblotting and flow cytometry to confirm Kv1.3 channel upregulation in lipopolysaccharide (LPS)-activated BV2 microglia and in brain mononuclear phagocytes freshly isolated from LPS-treated mice. Quantitative proteomics was performed on BV2 microglia treated with control, LPS, ShK-223 (highly selective Kv1.3 blocker), and LPS+ShK-223. Gene ontology (GO) analyses of Kv1.3-dependent LPS-regulated proteins were performed, and the most representative proteins and GO terms were validated. Effects of Kv1.3-blockade on LPS-activated BV2 microglia were studied in migration, focal adhesion formation, reactive oxygen species production, and phagocytosis assays. In vivo validation of protein changes and predicted molecular pathways were performed in a model of systemic LPS-induced neuroinflammation, employing antigen presentation and T cell proliferation assays. Informed by pathway analyses of proteomic data, additional mechanistic experiments were performed to identify early Kv1.3-dependent signaling and transcriptional events.

RESULTS

LPS-upregulated cell surface Kv1.3 channels in BV2 microglia and in microglia and CNS-infiltrating macrophages isolated from LPS-treated mice. Of 144 proteins differentially regulated by LPS (of 3141 proteins), 21 proteins showed rectification by ShK-223. Enriched cellular processes included MHCI-mediated antigen presentation (TAP1, EHD1), cell motility, and focal adhesion formation. In vitro, ShK-223 decreased LPS-induced focal adhesion formation, reversed LPS-induced inhibition of migration, and inhibited LPS-induced upregulation of EHD1, a protein involved in MHCI trafficking. In vivo, intra-peritoneal ShK-223 inhibited LPS-induced MHCI expression by CD11b⁺CD45^low microglia without affecting MHCI expression or trafficking of CD11b⁺CD45^high macrophages. ShK-223 inhibited LPS-induced MHCI-restricted antigen presentation to ovalbumin-specific CD8⁺ T cells both in vitro and in vivo. Kv1.3 co-localized with the LPS receptor complex and regulated LPS-induced early serine (S727) STAT1 phosphorylation.

CONCLUSIONS

We have unraveled novel molecular and functional roles for Kv1.3 channels in pro-inflammatory microglial activation, including a Kv1.3 channel-regulated pathway that facilitates MHCI expression and MHCI-dependent antigen presentation by microglia to CD8⁺ T cells. We also provide evidence for neuro-immunomodulation by systemically administered ShK peptides. Our results further strengthen the therapeutic candidacy of microglial Kv1.3 channels in neurologic diseases.

Stimulation of Natural Killer Cell-Mediated Tumor Immunity by an IL15/TGFβ-Neutralizing Fusion Protein

The clinical efficacy of immune cytokines used for cancer therapy is hampered by elements of the immunosuppressive tumor microenvironment such as TGFβ. Here we demonstrate that FIST15, a recombinant chimeric protein composed of the T-cell-stimulatory cytokine IL15, the sushi domain of IL15Rα and a TGFβ ligand trap, can overcome immunosuppressive TGFβ to effectively stimulate the proliferation and activation of natural killer (NK) and CD8⁺ T cells with potent antitumor properties. FIST15-treated NK and CD8⁺ T cells produced more IFNγ and TNFα compared with treatment with IL15 and a commercially available TGFβ receptor-Fc fusion protein (sTβRII) in the presence of TGFβ. Murine B16 melanoma cells, which overproduce TGFβ, were lysed by FIST15-treated NK cells in vitro at doses approximately 10-fold lower than NK cells treated with IL15 and sTβRII. Melanoma cells transduced to express FIST15 failed to establish tumors in vivo in immunocompetent murine hosts and could only form tumors in beige mice lacking NK cells. Mice injected with the same cells were also protected from subsequent challenge by unmodified B16 melanoma cells. Finally, mice with pre-established B16 melanoma tumors responded to FIST15 treatment more strongly compared with tumors treated with control cytokines. Taken together, our results offer a preclinical proof of concept for the use of FIST15 as a new class of biological therapeutics that can coordinately neutralize the effects of immunosuppressive TGFβ in the tumor microenvironment while empowering tumor immunity. Cancer Res; 76(19); 5683-95. ©2016 AACR.

GIFT4 fusokine converts leukemic B cells into immune helper cells

Background

Chronic lymphocytic leukemia (CLL) remains incurable with standard therapy, and is characterized by excessive expansion of monoclonal abnormal mature B cells and more regulatory immune properties of T cell compartment. Thus, developing novel strategies to enhance immune function merits further investigation as a possible therapy for CLL.

Methods

We generated a fusion cytokine (fusokine) arising from the combination of human GM-CSF and IL-4 (named GIFT4). Primary CLL cells were treated with GIFT4 or GM-CSG and IL-4 in vitro. GIFT4-triggered STAT5 signaling in CLL cells was examined by Western blot. The phenotype and secretome of GIFT4-treated CLL cells (GIFT4-CLL cells), and the immune stimulatory function of GIFT4-CLL cells on autologous T cells were analyzed by flow cytometry and luminex assay.

Results

GIFT4-CLL up-regulated the expression of co-stimulatory molecules CD40, CD80 and CD86 and adhesion molecule CD54. GIFT4-CLL cells secreted IL-1β, IL-6, ICAM-1 and substantial IL-2 relative to unstimulated CLL cells. GIFT4 treatment led to JAK1, JAK2 and JAK3-mediated hyper-phosphorylation of STAT5 in primary CLL cells, which is essential for GIFT4-triggered conversion of CLL cells. GIFT4-CLL cells directly propelled the expansion of autologous IFN-γ-producing CD314⁺ cytotoxic T cells in vitro, and that these could lyse autologous CLL cells. Furthermore, administration of GIFT4 protein promoted the expansion of human T cells in NOD-scid IL2Rγ^null immune deficient mice adoptively pre-transferred with peripheral blood mononuclear cells from subjects with CLL.

Conclusion

GIFT4 has potent capability to converts primary CLL cells into APC-like immune helper cells that initiate a T cell driven anti-CLL immune response.

Abstract A11: GIFT4-reprogrammed leukemic B cells for CLL immunotherapy

Chronic lymphocytic leukemia (CLL) is characterized by the clonal proliferation and accumulation of typically CD5 positive B cells. Recently, we have developed a novel GM-CSF and IL-4 Fusion Transgene (named GIFT4), and found that GIFT4 protein triggers a robust anti-tumor B cell response (Deng et al. Cancer Research 2014). Considering CLL B cells broadly express the IL-4 receptor, we tested the immune function of human GIFT4 on CLL B cells, and discovered that GIFT4 protein possess a unique pharmaceutical property and reprograms leukemic B cells into anti-CLL effectors with T-helper features. We showed that GIFT4 protein led to hyper-phosphorylation of STAT5 in primary human CLL cells, which involed cluster of JAK1, JAK2 and JAK3 signaling. GIFT4 treated CLL B-cells up-regulated the expression of co-stimulatory molecules CD40, CD80 and CD86. Inhibition of JAK signaling with specific inhibitors suppressed the expression of the co-stimulatory molecules. GIFT4-reprogrammed CLL cells secreted IL-1β, IL-6, ICAM1 and substantial IL-2. GIFT4-CLL B cells further propelled the expansion of IFN-γ-producing autologous cytotoxic T cells and NK cells in vitro. Administration of GIFT4 protein in immune deficient NSG mice decreased the survival of primary CLL cells from patients in murine circulation. Altogether, our data demonstrate that GIFT4 has potent anti-CLL immune function by reprograming leukemic B cells into anti-CLL helper cells. We propose that the newly bio-engineered fusokine GIFT4 could serve as a potential therapeutic for CLL treatment, and GIFT4-reprogrammed leukemic B cells could provide an entirely novel B-cell driven therapeutic strategy for the potential personalized cellular immunotherapy for individuals with CLL.

Citation Format: Jiusheng Deng, Jonathon Cohen, Andrea Pennati, Yuanqiang Wu, Shala Yuan, Christopher Flowers, Jacques Galipeau. GIFT4-reprogrammed leukemic B cells for CLL immunotherapy. [abstract]. In: Proceedings of the AACR Special Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(17 Suppl):Abstract nr A11.

Engineered fusokine GIFT4 licenses the ability of B cells to trigger a tumoricidal T-cell response

Engineered chimeric cytokines can generate gain-of-function activity in immune cells. Here, we report potent antitumor activity for a novel fusion cytokine generated by N-terminal coupling of GM-CSF to IL4, generating a fusokine termed GIFT4. B cells treated with GIFT4 clustered GM-CSF and IL4 receptors on the cell surface and displayed a pan-STAT hyperphosphorylation associated with acquisition of a distinct phenotype and function described to date. In C57BL/6J mice, administration of GIFT4 expanded endogenous B cells and suppressed the growth of B16F0 melanoma cells. Furthermore, B16F0 melanoma cells engineered to secrete GIFT4 were rejected immunologically in a B-cell-dependent manner. This effect was abolished when GIFT4-expressing B16F0 cells were implanted in B-cell-deficient mice, confirming a B-cell-dependent antitumor effect. Human GIFT4-licensed B cells primed cytotoxic T cells and specifically killed melanoma cells in vitro and in vivo. Taken together, our results demonstrated that GIFT4 could mediate expansion of B cells with potent antigen-specific effector function. GIFT4 may offer a novel immunotherapeutic tool and define a previously unrecognized potential for B cells in melanoma immunotherapy.

Kinetics of heme transfer by the Shr NEAT domains of Group A Streptococcus

The hemolytic Group A Streptococcus (GAS) is a notorious human pathogen. Shr protein of GAS participates in iron acquisition by obtaining heme from host hemoglobin and delivering it to the adjacent receptor on the surface, Shp. Heme is then conveyed to the SiaABC proteins for transport across the membrane. Using rapid kinetic studies, we investigated the role of the two heme binding NEAT modules of Shr. Stopped-flow analysis showed that holoNEAT1 quickly delivered heme to apoShp. HoloNEAT2 did not exhibit such activity; only little and slow transfer of heme from NEAT2 to apoShp was seen, suggesting that Shr NEAT domains have distinctive roles in heme transport. HoloNEAT1 also provided heme to apoNEAT2, by a fast and reversible process. To the best of our knowledge this is the first transfer observed between isolated NEAT domains of the same receptor. Sequence alignment revealed that Shr NEAT domains belong to two families of NEAT domains that are conserved in Shr orthologs from several species. Based on the heme transfer kinetics, we propose that Shr proteins modulate heme uptake according to heme availability by a mechanism where NEAT1 facilitates fast heme delivery to Shp, whereas NEAT2 serves as a temporary storage for heme on the bacterial surface.

Involvement of ionizable groups in catalysis of human liver glycolate oxidase

Glycolate oxidase is a flavin-dependent, peroxisomal enzyme that oxidizes alpha-hydroxy acids to the corresponding alpha-keto acids, with reduction of oxygen to H(2)O(2). In plants, the enzyme participates in photorespiration. In humans, it is a potential drug target for treatment of primary hyperoxaluria, a genetic disorder where overproduction of oxalate results in the formation of kidney stones. In this study, steady-state and pre-steady-state kinetic approaches have been used to determine how pH affects the kinetic steps of the catalytic mechanism of human glycolate oxidase. The enzyme showed a Ping-Pong Bi-Bi kinetic mechanism between pH 6.0 and 10.0. Both the overall turnover of the enzyme (k(cat)) and the rate constant for anaerobic substrate reduction of the flavin were pH-independent at pH values above 7.0 and decreased slightly at lower pH, suggesting the involvement of an unprotonated group acting as a base in the chemical step of glycolate oxidation. The second-order rate constant for capture of glycolate (k(cat)/K(glycolate)) and the K(d)((app)) for the formation of the enzyme-substrate complex suggested the presence of a protonated group with apparent pK(a) of 8.5 participating in substrate binding. The k(cat)/K(oxygen) values were an order of magnitude faster when a group with pK(a) of 6.8 was unprotonated. These results are discussed in the context of the available three-dimensional structure of GOX.

The ferredoxin-NADP+ reductase/ferredoxin electron transfer system of Plasmodium falciparum

In the apicoplast of apicomplexan parasites, plastidic-type ferredoxin and ferredoxin-NADP(+) reductase (FNR) form a short electron transport chain that provides reducing power for the synthesis of isoprenoid precursors. These proteins are attractive targets for the development of novel drugs against diseases such as malaria, toxoplasmosis, and coccidiosis. We have obtained ferredoxin and FNR of both Toxoplasma gondii and Plasmodium falciparum in recombinant form, and recently we solved the crystal structure of the P. falciparum reductase. Here we report on the functional properties of the latter enzyme, which differ markedly from those of homologous FNRs. In the physiological reaction, P. falciparum FNR displays a k(cat) five-fold lower than those usually determined for plastidic-type FNRs. By rapid kinetics, we found that hydride transfer between NADPH and protein-bound FAD is slower in the P. falciparum enzyme. The redox properties of the enzyme were determined, and showed that the FAD semiquinone species is highly destabilized. We propose that these two features, i.e. slow hydride transfer and unstable FAD semiquinone, are responsible for the poor catalytic efficiency of the P. falciparum enzyme. Another unprecedented feature of the malarial parasite FNR is its ability to yield, under oxidizing conditions, an inactive dimeric form stabilized by an intermolecular disulfide bond. Here we show that the monomerdimer interconversion can be controlled by oxidizing and reducing agents that are possibly present within the apicoplast, such as H(2)O(2), glutathione, and lipoate. This finding suggests that modulation of the quaternary structure of P. falciparum FNR might represent a regulatory mechanism, although this needs to be verified in vivo.

Effect of salt and pH on the reductive half-reaction of Mycobacterium tuberculosis FprA with NADPH

Despite a number of studies, the formation of the Michaelis complexes between ferredoxin-NADP (+) reductases and NADP(H) eluded detailed investigations by rapid kinetic techniques because of their high formation rates. Moreover, the reversible nature of the reaction of hydride ion transfer between these enzymes and NADPH prevented the obtainment of reliable estimates of the rate constant of the hydride transfer step. Here we show that by working at a high salt concentration, the mechanism of the reaction with NADPH of FprA, a Mycobacterium tuberculosis homologue of adrenodoxin reductase, is greatly simplified, making it amenable to investigation by rapid reaction techniques. The approach presented herein allowed for the first time the observation of the formation of the Michaelis complex between an adrenodoxin reductase-like enzyme and NADPH, and the determination of the related rate constants for association and dissociation. Furthermore, the rate constant for the reaction of hydride ion transfer between NADPH and FAD could be unambiguously assessed. It is proposed that the approach described should be applicable to other ferredoxin reductase enzymes, providing a valuable experimental tool for the study of their kinetic properties.

Structural and functional diversity of ferredoxin-NADP(+) reductases

Although all ferredoxin-NADP(+) reductases (FNRs) catalyze the same reaction, i.e. the transfer of reducing equivalents between NADP(H) and ferredoxin, they belong to two unrelated families of proteins: the plant-type and the glutathione reductase-type of FNRs. Aim of this review is to provide a general classification scheme for these enzymes, to be used as a framework for the comparison of their properties. Furthermore, we report on some recent findings, which significantly increased the understanding of the structure-function relationships of FNRs, i.e. the ability of adrenodoxin reductase and its homologs to catalyze the oxidation of NADP(+) to its 4-oxo derivative, and the properties of plant-type FNRs from non-photosynthetic organisms. Plant-type FNRs from bacteria and Apicomplexan parasites provide examples of novel ways of FAD- and NADP(H)-binding. The recent characterization of an FNR from Plasmodium falciparum brings these enzymes into the field of drug design.

Enzymatic oxidation of NADP+ to its 4-oxo derivative is a side-reaction displayed only by the adrenodoxin reductase type of ferredoxin-NADP+ reductases

We have previously shown that Mycobacterium tuberculosis FprA, an NADPH-ferredoxin reductase homologous to mammalian adrenodoxin reductase, promotes the oxidation of NADP(+) to its 4-oxo derivative 3-carboxamide-4-pyridone adenine dinucleotide phosphate [Bossi RT, Aliverti A, Raimondi D, Fischer F, Zanetti G, Ferrari D, Tahallah N, Maier CS, Heck AJ, Rizzi M et al. (2002) Biochemistry41, 8807-8818]. Here, we provide a detailed study of this unusual enzyme reaction, showing that it occurs at a very slow rate (0.14 h(-1)), requires the participation of the enzyme-bound FAD, and is regiospecific in affecting only the C4 of the NADP nicotinamide ring. By protein engineering, we excluded the involvement in catalysis of residues Glu214 and His57, previously suggested to be implicated on the basis of their localization in the three-dimensional structure of the enzyme. Our results substantiate a catalytic mechanism for 3-carboxamide-4-pyridone adenine dinucleotide phosphate formation in which the initial and rate-determining step is the nucleophilic attack of the nicotinamide moiety by an active site water molecule. Whereas plant-type ferredoxin reductases were unable to oxidize NADP(+), the mammalian adrenodoxin reductase also catalyzed this unusual reaction. Thus, the 3-carboxamide-4-pyridone adenine dinucleotide phosphate formation reaction seems to be a peculiar feature of the mitochondrial type of ferredoxin reductases, possibly reflecting conserved properties of their active sites. Furthermore, we showed that 3-carboxamide-4-pyridone adenine dinucleotide phosphate is good ligand and a competitive inhibitor of various dehydrogenases, making this nucleotide analog a useful tool for the characterization of the cosubstrate-binding site of NADPH-dependent enzymes.

Role of the His57-Glu214 ionic couple located in the active site of Mycobacterium tuberculosis FprA

Mycobacterium tuberculosis FprA is a NADPH-ferredoxin reductase, functionally and structurally similar to the mammalian adrenodoxin reductase. It is presumably involved in supplying electrons to one or more of the pathogen's cytochrome P450s through reduced ferredoxins. It has been proposed on the basis of crystallographic data (Bossi, R. T., et al. (2002) Biochemistry 41, 8807-8818) that the highly conserved His57 and Glu214 whose side chains are H-bonded are involved in catalysis. Both residues were individually changed to nonionizable amino acyl residues through site-directed mutagenesis. Steady-state kinetics showed that the role of Glu214 in catalysis is negligible. On the contrary, the substitutions of His57 markedly impaired the catalytic efficiency of FprA for ferredoxin in the physiological reaction. Furthemore, they decreased the k(cat)/K(m) value for NADPH in the ferricyanide reduction. Rapid-reaction (stopped-flow) kinetic analysis of the isolated reductive half-reaction of wild-type and His57Gln forms of FprA with NADPH and NADH allowed a detailed description of the mechanism of enzyme-bound FAD reduction, with the identification of the intermediates involved. The His57Gln mutation caused a 6-fold decrease in the rate of hydride transfer from either NADPH or NADH to the enzyme-bound FAD cofactor. The 3D structure of FprA-H57Q, obtained at 1.8 A resolution, explains the inefficient hydride transfer of the mutant in terms of a suboptimal geometry of the nicotinamide-isoalloxazine interaction in the active site. These data demonstrate the role of His57 in the correct binding of NADPH to FprA for the subsequent steps of the catalytic cycle to proceed at a high rate.

Easy Oxidation and Nitration of Human Myoglobin by Nitrite and Hydrogen Peroxide

The modification of human myoglobin (HMb) by reaction with nitrite and hydrogen peroxide has been investigated. This reaction is important because NO(2) (-) and H(2)O(2) are formed in vivo under conditions of oxidative and nitrative stress, where protein derivatization has been often observed. The abundance of HMb in tissues and in the heart makes it a potential source and target of reactive species generated in the body. The oxidant and nitrating species produced by HMb/H(2)O(2)/NO(2) (-) are nitrogen dioxide and peroxynitrite, which can react with exogenous substrates and endogenous protein residues. Tandem mass analysis of HMb modified by stoichiometric amounts of H(2)O(2) and NO(2) (-) indicated the presence of two endogenous derivatizations: oxidation of C110 to sulfinic acid (76 %) and nitration of Y103 to 3-nitrotyrosine (44 %). When higher concentrations of NO(2) (-) and H(2)O(2) were used, nitration of Y146 and of the heme were also observed. The two-dimensional gel-electrophoretic analysis of the modified HMbs showed spots more acidic than that of wild-type HMb, a result in agreement with the formation of sulfinic acid and nitrotyrosine residues. By contrast, the reaction showed no evidence for the formation of protein homodimers, as observed in the reaction of HMb with H(2)O(2) alone. Both HMb and the modified HMb are active in the H(2)O(2)/NO(2) (-)-dependent nitration of exogenous phenols. Their catalytic activity is quite similar and the endogenous modifications of HMb therefore have little effect on the reactivity of the protein intermediates.

Engineering peroxidase activity in myoglobin: the haem cavity structure and peroxide activation in the T67R/S92D mutant and its derivative reconstituted with protohaemin-l-histidine

Atomic co-ordinates and structure factors for the T67R/S92D metMbCN mutant have been deposited with the Protein Data Bank, under accession codes 1h1x and r1h1xsf, respectively. Protein engineering and cofactor replacement have been employed as tools to introduce/modulate peroxidase activity in sperm whale Mb (myoglobin). Based on the rationale that haem peroxidase active sites are characterized by specific charged residues, the Mb haem crevice has been modified to host a haem-distalpropionate Arg residue and a proximal Asp, yielding the T67R/S92D Mb mutant. To code extra conformational mobility around the haem, and to increase the peroxidase catalytic efficiency, the T67R/S92D Mb mutant has been subsequently reconstituted with protohaem-L-histidine methyl ester, yielding a stable derivative, T67R/S92D Mb-H. The crystal structure of T67R/S92D cyano-metMb (1.4 A resolution; R factor, 0.12) highlights a regular haem-cyanide binding mode, and the role for the mutated residues in affecting the haem propionates as well as the neighbouring water structure. The conformational disorder of the haem propionate-7 is evidenced by the NMR spectrum of the mutant. Ligand-binding studies show that the iron(III) centres of T67R/S92D Mb, and especially of T67R/S92D Mb-H, exhibit higher affinity for azide and imidazole than wild-type Mb. In addition, both protein derivatives react faster than wild-type Mb with hydrogen peroxide, showing higher peroxidase-like activity towards phenolic substrates. The catalytic efficiency of T67R/S92D Mb-H in these reactions is the highest so far reported for Mb derivatives. A model for the protein-substrate interaction is deduced based on the crystal structure and on the NMR spectra of protein-phenol complexes.

Celibacy and fertility rates in patients with major affective disorders: the relevance of delusional symptoms and suicidal behaviour

The celibacy and fertility rates of 186 patients with major affective disorders were analysed as a function of the presence or absence of histories of mood congruent delusions or suicidal behaviour in the depressive phases of the disease. Both delusional and suicidal histories were irrelevant to celibacy rates. On the contrary, delusional depressives had a reduced incidence of cases with 2 or more children and suicide attempters had both a lower frequency of high-fertility cases and a smaller mean number of children than nonattempters. The differences were apparently not attributable to the length of the fertile period of life spent in illness.

Heterogeneity of major affective disorders. Biological and clinical evidence

In this paper we summarize the results of our recent and present research focused on analyzing the correlations between neurochemical, pharmacological and clinical parameters in patients with Major Depression. There is evidence that: a) pretreatment urinary MHPG is a useful predictor for clinical response to tricyclic antidepressants and to long-term lithium treatment; b) urinary MHPG is positively correlated to the age at onset of the disease; c) previous responses to tricyclics and age at onset of affective illness are supplementary tools for predicting the effectiveness of lithium and antidepressant drugs; d) platelet alpha-2-adrenoceptor density is inversely correlated with both urinary MHPG and age at onset; e) cerebral ventricular size is positively correlated with urinary MHPG and age at onset and may discriminate between patients with different outcomes on lithium prophylaxis; f) low MHPG excretors are more likely to have suffered from stressful life events in early childhood than normal-to-high excretors. Taken together, these results lend strong support to the hypothesis that Major Affective Disorder is a heterogeneous illness and that inherently different subgroups of affective patients can be recognized.

Platelet alpha 2-adrenoceptors in major depression: relationship with urinary 4-hydroxy-3-methoxyphenylglycol and age at onset

Platelet alpha 2-adrenoceptor number and affinity were measured in 31 drug-free patients with major depressive illness utilizing 3H-clonidine as ligand. A significant negative correlation was found between number of alpha 2-adrenoceptors, baseline urinary 4-hydroxy-3-methoxyphenylglycol (MHPG) excretion, present age and age at onset of the disease. Kd did not correlate with any of these variables not with the Bmax of platelet alpha 2-adrenergic binding. Multiple regression analysis, with MHPG and age at onset as independent variables, explained variance for alpha 2-adrenoceptor density better than single regression (from 19% for MHPG and 30% for age at onset to 40%), with the addition of both these variables being significant.