GIFT-1, a phase IIa clinical trial to test the safety and efficacy of IFNγ administration in FRDA patients

Friedreich's ataxia is an autosomal recessive progressive degenerative disorder caused by deficiency of the protein frataxin. The most common genetic cause is a homozygotic expansion of GAA triplets within intron 1 of the frataxin gene leading to impaired transcription. Preclinical in vivo and in vitro studies have shown that interferon gamma (IFNγ) is able to up-regulate the expression of frataxin gene in multiple cell types. We designed a phase IIa clinical trial, the first in Italy, aimed at assessing both safety and tolerability of IFNγ in Friedreich's patients and ability to increase frataxin levels in peripheral blood mononuclear cells. Nine patients (6 female and 3 males aged 21-38 years) with genetically confirmed disease were given 3 subcutaneous escalating doses (100, 150 and 200 μg) of IFNγ (human recombinant interferon 1 b gamma, trade name IMUKIN(®)), over 4 weeks. The primary end-point was the assessment of the safety and tolerability of IFNγ by means of standard clinical and hematological criteria. The secondary end-point was the detection of changes of frataxin levels in peripheral blood mononuclear cells after each single escalating dose of the drug. IFNγ was generally well tolerated, the main adverse event was hyperthermia/fever. Although, increases in frataxin levels could be detected in a minority of patients, these changes were not significant. A large phase III multicenter, randomized clinical trial with IFNγ in Friedreich's ataxia patients is currently ongoing. This study is expected to conclusively address the clinical efficacy of IFNγ therapy in patients with Friedreich's ataxia.

Interferon gamma upregulates frataxin and corrects the functional deficits in a Friedreich ataxia model

Friedreich's ataxia (FRDA) is the most common hereditary ataxia, affecting ∼3 in 100 000 individuals in Caucasian populations. It is caused by intronic GAA repeat expansions that hinder the expression of the FXN gene, resulting in defective levels of the mitochondrial protein frataxin. Sensory neurons in dorsal root ganglia (DRG) are particularly damaged by frataxin deficiency. There is no specific therapy for FRDA. Here, we show that frataxin levels can be upregulated by interferon gamma (IFNγ) in a variety of cell types, including primary cells derived from FRDA patients. IFNγ appears to act largely through a transcriptional mechanism on the FXN gene. Importantly, in vivo treatment with IFNγ increases frataxin expression in DRG neurons, prevents their pathological changes and ameliorates the sensorimotor performance in FRDA mice. These results disclose new roles for IFNγ in cellular metabolism and have direct implications for the treatment of FRDA.

Frataxin participates to the hypoxia-induced response in tumors

Defective expression of frataxin is responsible for the degenerative disease Friedreich's ataxia. Frataxin is a protein required for cell survival since complete knockout is lethal. Frataxin protects tumor cells against oxidative stress and apoptosis but also acts as a tumor suppressor. The molecular bases of this apparent paradox are missing. We therefore sought to investigate the pathways through which frataxin enhances stress resistance in tumor cells. We found that frataxin expression is upregulated in several tumor cell lines in response to hypoxic stress, a condition often associated with tumor progression. Moreover, frataxin upregulation in response to hypoxia is dependent on hypoxia-inducible factors expression and modulates the activation of the tumor-suppressor p53. Importantly, we show for the first time that frataxin is in fact increased in human tumors in vivo. These results show that frataxin participates to the hypoxia-induced stress response in tumors, thus implying that modulation of its expression could have a critical role in tumor cell survival and/or progression.

In vivo maturation of human frataxin

The defective expression of frataxin causes the hereditary neurodegenerative disorder Friedreich's ataxia (FRDA). Human frataxin is synthesized as a 210 amino acid precursor protein, which needs proteolytic processing into mitochondria to be converted into the functional mature form. In vitro processing of human frataxin was previously described to yield a 155 amino acid mature form, corresponding to residues 56-210 (frataxin(56-210)). Here, we studied the maturation of frataxin by in vivo overexpression in human cells. Our data show that the main form of mature frataxin is generated by a proteolytic cleavage between Lys80 and Ser81, yielding a 130 amino acid protein (frataxin(81-210)). This maturation product corresponds to the endogenous frataxin detected in human heart, peripheral blood lymphocytes or dermal fibroblasts. Moreover, we demonstrate that frataxin(81-210) is biologically functional, as it rescues aconitase defects in frataxin-deficient cells derived from FRDA patients. Importantly, our data indicate that frataxin(56-210) can be produced in vivo when the primary 80-81 maturation site is unavailable, suggesting the existence of proteolytic mechanisms that can actively control the size of the mature product, with possible functional implications.

A pool of extramitochondrial frataxin that promotes cell survival

Frataxin is a mitochondrial protein involved in iron metabolism. Defective expression of frataxin causes Friedreich ataxia (FA), an inherited degenerative syndrome characterized by ataxia, cardiomyopathy, and high incidence of diabetes. Here we report that frataxin-deficient cells are more prone to undergo stress-induced mitochondrial damage and apoptosis, while the overexpression of frataxin confers protection to a variety of cell types. Moreover, we reveal the existence of an extramitochondrial pool of frataxin, which can efficiently prevent mitochondrial damage and apoptosis in different cellular systems. Remarkably, extramitochondrial frataxin can fully replace mitochondrial frataxin in promoting survival of FA cells.

Ceramide catabolism critically controls survival of human dendritic cells

The regulation of dendritic cell (DC) survival is crucial for the modulation of adaptive immunity. Ceramide is a lipid mediator of the stress response, which accumulates intracellularly during DC differentiation. We found that ceramide levels are tightly regulated in human DCs and that the pharmacological inhibition of enzymes responsible for ceramide catabolism, such as ceramidases and sphingosine kinases, sensitizes DCs to ceramide-induced cell death. It is important that inhibition of sphingosine kinases, during lipopolysaccharide stimulation, causes extensive ceramide accumulation and death of DCs. These data indicate that ceramide catabolism regulates survival of human DCs and reveal novel potential targets for the pharmacological manipulation of the immune response.

Calnexin suppresses GD3 synthase-induced apoptosis

An accelerated activity of the GD3 synthase (ST8), with consequent GD3 accumulation, is part of the response to environmental stressors in different cell types. Depending on specific, yet largely undefined, cellular settings, this can be followed by adaptation or apoptosis, the latter mostly due to GD3-induced mitochondrial damage. Here we show that subcellular localization of ST8 could significantly affect the biological outcome of GD3 accumulation. Binding to the molecular chaperone calnexin causes the retention of ST8 within the endoplasmic reticulum (ER) and prevents its relocalization to the Golgi. Calnexin-dependent ER retention does not affect the activity of ST8; yet the de novo synthesized GD3 largely fails to reach the mitochondria. Accordingly, overexpression of calnexin suppresses the pro-apoptotic activity of ST8, while the loss of calnexin sensitizes the cells to ST8-induced apoptosis. Reconstitution of calnexin confers protection to deficient cells. Thus, calnexin controls the biological outcome of GD3 accumulation and reveals a novel role in the stress response.

A caspaselike activity is triggered by LPS and is required for survival of human dendritic cells

Bacterial endotoxin (lipopolysaccharide [LPS]) is a potent inducer of human dendritic cell (DC) maturation and survival. Here we show that immature DCs exposed to LPS trigger an early and sustained caspase-like activity, which can be blocked by zVAD (z-Val-Ala-Asp), in the absence of detectable caspase 8 and caspase 10 activation, or poly(ADP-ribose) polymerase (PARP)-cleaving activity. Preventing LPS-induced caspase-like activation in DC results in massive cell death. Importantly, triggering of the caspase-like activity is required for LPS-induced activation of extracellular signal-regulated kinases (ERKs) and for LPS-induced up-regulation of cFLIP (Fas-associating protein with death domain-like interleukin-1 beta-converting enzyme [FLICE]-like inhibitory protein). Therefore, a caspase-dependent pathway initiated by LPS controls survival of human DCs.

Acetylation suppresses the proapoptotic activity of GD3 ganglioside

GD3 synthase is rapidly activated in different cell types after specific apoptotic stimuli. De novo synthesized GD3 accumulates and contributes to the apoptotic program by relocating to mitochondrial membranes and inducing the release of apoptogenic factors. We found that sialic acid acetylation suppresses the proapoptotic activity of GD3. In fact, unlike GD3, 9-O-acetyl-GD3 is completely ineffective in inducing cytochrome c release and caspase-9 activation on isolated mitochondria and fails to induce the collapse of mitochondrial transmembrane potential and cellular apoptosis. Moreover, cells which are resistant to the overexpression of the GD3 synthase, actively convert de novo synthesized GD3 to 9-O-acetyl-GD3. The coexpression of GD3 synthase with a viral 9-O-acetyl esterase, which prevents 9-O-acetyl-GD3 accumulation, reconstitutes GD3 responsiveness and apoptosis. Finally, the expression of the 9-O-acetyl esterase is sufficient to induce apoptosis of glioblastomas which express high levels of 9-O-acetyl-GD3. Thus, sialic acid acetylation critically controls the proapoptotic activity of GD3.

Mitochondria as sensors of sphingolipids

Much of the action in the mammalian apoptotic program takes place at the mitochondrial level. Physicochemical characteristics and integrity of mitochondrial membranes may play a crucial role in the recruitment and multimerization of pro-apoptotic Bcl-2 family members, opening of the permeability transition pore complex (PTPC) and the release of mitochondrial components which trigger the 'intrinsic' pathways of cellular apoptosis and activate executioner caspases. Recent evidence has accumulated pointing toward the mitochondrial membranes as the key targets for lipid and glycolipid mediators of stress-induced apoptosis. Mitochondrial membranes may thus act as 'sensors' of cellular stress by quantitating the local accumulation of specific lipids and glycolipids. Acute accumulation of ceramides, directly or indirectly, profoundly affects mitochondrial functions. GD3 ganglioside, a glycolipid which is actively synthesized and transiently accumulates in the early stages of apoptosis, relocates to the mitochondrial membranes causing the opening of the PTPC and the release of apoptogenic factors. Mitochondrial membranes appear to represent a common destination where protein and glycolipid mediators of stress converge and where crucial decisions about cellular adaptation or apoptotic cell death are taken.

UVB-induced apoptosis of human dendritic cells: contribution by caspase-dependent and caspase-independent pathways

Dendritic cells (DCs) play a central role in the initiation and regulation of the immune response. The modalities by which DCs are committed to undergo apoptosis are poorly defined. Here it is shown that, unlike death receptor ligands, UVB radiation triggers apoptosis of human DCs very efficiently. UVB exposure is followed by the activation of caspases 8, 9, and 3, by the loss of mitochondrial transmembrane potential (deltaPsim), and by cellular and nuclear fragmentation. Caspase inhibitors substantially prevented the occurrence of cellular and nuclear fragmentation but had no effect on UVB-induced deltaPsim dissipation. Importantly, mature DCs (MDCs) displayed relative resistance to UVB; UVB-induced caspase activation and apoptosis were substantially delayed compared to immature DCs (IDCs). Resistance correlated with the strong up-regulation of cellular FLIP and bcl2 observed in MDCs compared to IDCs.

GD3 ganglioside directly targets mitochondria in a bcl-2-controlled fashion

Lipid and glycolipid diffusible mediators are involved in the intracellular progression and amplification of apoptotic signals. GD3 ganglioside is rapidly synthesized from accumulated ceramide after the clustering of death-inducing receptors and triggers apoptosis. Here we show that GD3 induces dissipation of DeltaPsim and swelling of isolated mitochondria, which results in the mitochondrial release of cytochrome c, apoptosis inducing factor, and caspase 9. Soluble factors released from GD3-treated mitochondria are sufficient to trigger DNA fragmentation in isolated nuclei. All these effects can be blocked by cyclosporin A, suggesting that GD3 is acting at the level of the permeability transition pore complex. We found that endogenous GD3 accumulates within mitochondria of cells undergoing apoptosis after ceramide exposure. Accordingly, suppression of GD3 synthase (ST8) expression in intact cells substantially prevents ceramide-induced DeltaPsim dissipation, indicating that endogenously synthesized GD3 induces mitochondrial changes in vivo. Finally, enforced expression of bcl-2 significantly prevents GD3-induced mitochondrial changes, caspase 9 activation, and apoptosis. These results show that mitochondria are a key destination for apoptogenic GD3 ganglioside along the lipid pathway to programmed cell death and indicate that relevant GD3 targets are under bcl-2 control.

Caspases mediate retinoic acid-induced degradation of the acute promyelocytic leukemia PML/RARalpha fusion protein

All-trans-retinoic acid (RA) treatment induces morphological remission in acute promyelocytic leukemia (APL) patients carrying the t(15;17) and expressing the PML/RARalpha product by inducing terminal differentiation of the leukemic clone. RA treatment induces downregulation of PML/RARalpha and reorganization of the PML-nuclear bodies. These events have been proposed to be essential for the induction of APL cell differentiation by RA. Here, we show that in the APL-derived NB4 cell line as well as in myeloid precursor U937 cells expressing the PML/RARalpha (U937/PR9) and in blasts from APL patients, the PML/RARalpha fusion protein is cleaved by a caspase 3-like activity induced by RA treatment. In fact, a caspase 3-like activity is detectable in PML/RARalpha expressing cells after RA treatment, and selective caspase inhibitor peptides are able to prevent the RA-induced degradation of the fusion protein in vivo and in vitro. Using recombinant caspases and PML/RARalpha deletion mutants we mapped a caspase 3 cleavage site (Asp 522) within the alpha-helix region of the PML component of the fusion protein. The extent of PML/RARalpha cleavage directly correlates with the ability of RA to restore the normal PML nuclear bodies (NBs) pattern. However, RA-induced differentiation is not prevented by the persistence of the fusion product and occurs in the absence of normally structured PML NBs. These results indicate that PML/RARalpha is directly involved in conferring RA sensitivity of APL cells and that the RA-induced reassembly of PML NBs is the consequence of the disappearance of PML/RARalpha.

Requirement for GD3 ganglioside in CD95- and ceramide-induced apoptosis

Gangliosides participate in development and tissue differentiation. Cross-linking of the apoptosis-inducing CD95 protein (also called Fas or APO-1) in lymphoid and myeloid tumor cells triggered GD3 ganglioside synthesis and transient accumulation. CD95-induced GD3 accumulation depended on integral receptor "death domains" and on activation of a family of cysteine proteases called caspases. Cell-permeating ceramides, which are potent inducers of apoptosis, also triggered GD3 synthesis. GD3 disrupted mitochondrial transmembrane potential (DeltaPsim), and induced apoptosis, in a caspase-independent fashion. Transient overexpression of the GD3 synthase gene directly triggered apoptosis. Pharmacological inhibition of GD3 synthesis and exposure to GD3 synthase antisense oligodeoxynucleotides prevented CD95-induced apoptosis. Thus, GD3 ganglioside mediates the propagation of CD95-generated apoptotic signals in hematopoietic cells.

Reversal of Mu gem2ts-induced mutations

Mutations induced by the integration of a Mu gem2ts mutant prophage can revert at frequencies around 1 x 10(-6), more than 10(4)-fold higher than that obtained with Mu wild-type. Several aspects characterize Mu gem2ts precise excision: (i) the phage transposase is not involved; (ii) the RecA protein is not necessary; and (iii) revertants remain lysogenic with the prophage inserted elsewhere in the host genome. In addition, prophage re-integration seems to be non-randomly distributed, whereas Mu insertion into the host genome is a transposition event without any sequence specificity. In this paper, we describe that the site of re-integration somehow depends on the original site of insertion. Two alternative models are proposed to explain the strong correlation between donor and receptor sites.

[Mitochondrial disease and complete heart block. Kearns-Sayre syndrome. Description of a case]

Defects of the mitochondrial respiratory chain form a clinically and biochemically heterogeneous group of diseases. Mitochondrial diseases include myopathies and multisystem disorders that are defined either by biochemical abnormalities of the mitochondria or by the presence of "ragged red fibers" in muscle-biopsy specimens stained with modified Gomori's trichrome stain. Several syndromes have been identified. Typical Kearns-Sayre syndrome is a sporadic condition that is characterized by an onset before the age of 20, progressive external ophthalmoplegia, pigmentary retinopathy and cardiac disorders. Mitochondrial DNA deletions were found in patient with Kearns-Sayre syndrome. We report the case of a 33 year-old woman, with neuromuscular syndrome of the Kearns-Sayre type, insulin-sensitive diabetes and complete heart block, who was implanted a pacemaker.

[Primary malignant lymphoma of the heart. Description of a case and review of the literature]

Primary cardiac tumors are rare. Approximately 25% of primary cardiac tumors are malignant, with the majority of these being sarcomas. Primary lymphoma of the heart is a very rare malignancy, usually recognized at autopsy or fatal within a few weeks of diagnosis. we report the case of a patient with diffuse large uncleaved cell lymphoma of the heart who had dyspnea, distention of the neck veins, edema of the face and arms. The diagnosis in this patient was aided by 2D-echocardiography, CT scan of the chest and superior vena caval angiography. The diagnosis was confirmed at operation and by histological examination. Surgical procedures were only palliative and aimed at prolonging life. However, prognosis remained severe and unchanged.

[A left atrial myxoma. The clinical aspects]

The paper describes a case of left atrial myxoma, which was unidentified for many years after the onset of symptoms, with emphasis on the necessity for instrumental investigations (particularly M-mode and two-dimensional echocardiography) in order to obtain an accurate and prompt diagnosis of these affections when the patient's clinical history justifies the suspicion.

[Syncopal attacks caused by paroxysmal atrioventricular block in patients with systemic lupus erythematosus]

The case is described of a young woman with SLE and lipothymic and syncopal attacks during second degree paroxysmal AVB or low frequency junctional rhythm. The case was cured by the implantation of a permanent multi-programmable pace-maker.