Lambertos Escudero, Ana

Person:
Lambertos Escudero, Ana

Name

Lambertos Escudero, Ana

publication.page.department

Universidad de Murcia. Departamento de Bioquímica y Biología Molecular"B" e Inmunología

Full item page

Search Results

Now showing 1 - 9 of 9

Open Access
Análisis de la expresión y función del inhibidor de antizimas 2 (AZIN2) en ratones transgénicos : estudio de nuevos ortólogos y parálogos de AZIN2
(2016-11-29) Lambertos Escudero, Ana; Peñafiel García, Rafael; Facultad de Medicina
BACKGROUND AND AIMS Polyamines are ubiquitous organic cations that play multiple essential roles in mammalian physiology. Ornithine decarboxylase (ODC) is the rate limiting enzyme in polyamine biosynthesis and it is regulated by antizymes, a family of small proteins whose synthesis is stimulated by high polyamine levels. AZs bind to ODC inhibiting its enzymatic activity and target it for degradation by the 26S proteasome. AZs are themselves regulated by another ODC-related family named antizyme inhibitors (AZINs), consisting of two members: AZIN1 and AZIN2. These proteins lack enzymatic activity but they bind to AZs with higher affinity than ODC, counteracting the effects of antizymes on ODC. AZIN1 is a ubiquitous protein that participates in the regulation of polyamine metabolism and cell growth and its disruption in mice causes death soon after birth. AZIN2 is mainly expressed in brain and testis, followed by other secretory tissues and cells. Although the physiological role of AZIN2 is mostly unknown, some data suggests that it is involved in cell growth, vesicular trafficking, secretion and spermiogenesis. In order to study the expression pattern of AZIN2 and its physiological role in mouse, AZIN2 KO mice were generated by the insertion of a beta geo cassette, resulting in a fused protein formed by the N-terminus extreme of AZIN2 and the reporter enzyme β-galactosidase. On the other hand, advances in genome sequencing revealed the existence of many orthologous of Azin2, and a new paralogue of Azin2 in mouse, named Gm853, whose study by transient transfected cells is a main aim of the present work. RESULTS AND CONCLUSIONS 1. Expression of the reporter gene lacZ in tissues of mice lacking Azin2. AZIN2 KO generated mice provide qualitative and quantitative information about the expression and function of AZIN2. Hystochemical and biochemical analysis of the reporter β-galactosidase activity in different tissues of AZIN2 KO mice confirmed significant expression of AZIN2 in epidydymis, adrenal glands, pancreas, heart, lung and eyes, in addition to testis and brain, pointing to secretory regions. However, none of the KO tissues examined showed significantly variation in polyamine content. Finally, the microarray analysis of gene differential expression between WT and KO mice did not show common changes, except the marked reduction of Azin2 expression. 2. The role of AZIN2 in male reproductive system. Hystological sections from testis and epididymis of AZIN2 KO and WT mice showed that AZIN2 was mainly expressed in haploid cells but also in Leydig cells, suggesting that AZIN2 is required not only for the synthesis but also for the function of mature sperm cells. Besides, the sperm motility test revealed that most AZIN2 KO sperm cells were not able to move across the test medium. However, this deficiency in motor skills did not have major consequences in male fertility, as AZIN2 KO mice demonstrated to be as fertile as their WT counterparts. Finally, the deprivation of AZIN2 in male reproductive system was also associated to decreased biosynthesis and secretion of testosterone. 3. Expression and function of AZIN2 in other secretory cells and tissues. Phenotypic analysis of AZIN2 KO mice. The role of AZIN2 in murine physiology was analysed in other secretory cells and tissues apart from testis by comparing the gain or the loss of functions in AZIN2 KO mice. In brain, AZIN2 prevails in the cerebellum and hippocampus areas and its disruption in these areas correlates with a deficient motor function in mice. The expression of AZIN2 in adrenal glands and pancreas was restricted to the adrenal medulla and to Langerhans islets, respectively. In other tissues such as heart, eyes, lung and kidney, the expression of AZIN2 was also restricted to specific types of cells. In pancreas, the absence of AZIN2 generates a slight hyperglycemia associated to impaired synthesis and secretion of insulin from β cells. 4. Structural and functional properties of Xenopus Azin2. Studies about ODC in Xenopus reveal the existence of two homologous proteins named XODC1 and XODC2, with different spatial and temporary patterns of expression. XODC2 appears on gene databases as XAZIN2, thus, it is considered an orthologous of mAZIN2 and hAZIN2. Unlike mAZIN2, the orthologous of AZIN2 in Xenopus laevis (xlAZIN2) is degraded by AZ1 and possesses decarboxylase activity of ornithine and lysine, showing higher affinity for lysine than for ornithine. The comparative analysis of xlAZIN2 with mODC and mAZIN2 revealed additional similarities with mODC, based on the cytosolic subcellular localization and the ability to form aggregates such as homotetramers. Similarly to mODC, xlAZIN2 stimulates agmatine uptake, decreases that of putrescine and spermidine and presents a short half-life, lower than 30 minutes. 5. Study of mouse Gm853, a new paralogue of Odc and Azin2. Comparative analysis of protein sequences from ODC paralogues revealed GM853 as a new homologue protein of ODC and AZINs in mouse, presenting all conserved residues for enzymatic activity. Experiments with transfected cells demonstrated that GM853 is not an antizyme inhibitor as it does not prevent the interaction between ODC and AZ1. Otherwise, it is a very stable protein mainly located in the cytosol and it is able to form homodimers and homotetramers but no heterodimers with other paralogues. Besides, GM853 presents enzymatic activity, being the first decarboxylase for L-Leucine described in mammals. The expression of GM853 in mice is restricted to renal tissue with higher representation in male kidneys, related to increased levels of testosterone. The product of Leucine decarboxylation is the isopenthylamine and it is rapidly excreted with urine. ANTECEDENTES Y OBJETIVOS Las poliaminas son cationes orgánicos presentes en todas las células con funciones esenciales en la fisiología de todos los mamíferos. Ornitina descarboxilasa (ODC) es la enzima limitante en la biosíntesis de poliaminas y está regulada por los antizimas (AZs), una familia de pequeñas proteínas cuya síntesis es estimulada por las propias poliaminas. Los AZs se unen a ODC inhibiendo su actividad enzimática y la conducen al proteasoma 26S para su degradación. Los AZs son a su vez regulados por otra familia de proteínas relacionadas con ODC, denominadas inhibidores de antizimas (AZINs), formada por dos miembros: AZIN1 y AZIN2. Estas proteínas carecen de actividad enzimática pero se unen a los AZs con más afinidad que ODC, contrarrestando los efectos de los antizimas sobre ODC. AZIN1 es una proteína ubicua que participa en la regulación del metabolismo de poliaminas y el crecimiento celular y su abatimiento en ratones causa la muerte poco después de nacer. AZIN2 se expresa fundamentalmente en cerebro y testículos, además de otros tejidos y células secretoras. Aunque el papel fisiológico de AZIN2 no se conoce con certeza, algunos experimentos sugieren que está implicado en el crecimiento celular, el tráfico vesicular, secreción y espermatogénesis. Con el fin de estudiar el patrón de expresión de AZIN2 y su implicación fisiológica en ratón, se generaron ratones KO de AZIN2 mediante la inserción de un cassette beta geo, que dio lugar a una proteína recombinante formada por el extremo N-terminal de AZIN2 y la enzima reportera β-galactosidasa. Por otro lado, los avances en el ámbito de la secuenciación de genomas, han revelado la existencia de un gran número de ortólogos de Azin2, así como un nuevo parálogo de Azin2 en ratón, denominado Gm853, cuyo estudio mediante células transfectadas también es objeto de esta tesis doctoral. RESULTADOS Y CONCLUSIONES 1. Expresión del gen reportero lacZ en tejidos de ratones con abatimiento de Azin2. El modelo de ratón transgénico con abatimiento del gen Azin2 generado, permitía el estudio de la expresión y posible función de la proteína AZIN2. El análisis histoquímico y bioquímico de la actividad β-galactosidasa en tejidos de ratones KO de AZIN2 confirmó la expresión de AZIN2 en epidídimo, glándula adrenal, páncreas, corazón, pulmón y ojos, aparte de testículo y cerebro, apuntando a células secretoras. Sin embargo, en ninguno de los tejidos estudiados en ratones deficientes en AZIN2 se observó reducción significativa de los niveles tisulares de poliaminas. Finalmente, el estudio comparativo de la expresión de genes entre ratones WT y KO mediante microarrays, no mostró cambios comunes en todos ellos salvo la marcada reducción de la expresión de Azin2. 2. The role of AZIN2 in male reproductive system. El análisis histoquímico de secciones de testículos y epidídimos WT y KO de AZIN2 mostró que AZIN2 se expresa fundamentalmente en células haploides, pero también en las células de Leydig, sugiriendo su participación no solo enla síntesis sino también en la maduración de los espermatozoides. Además, el test de movilidad espermática mostró que la mayoría de los espermatozoides KO de AZIN2 no eran capaces de desplazarse en el medio de ensayo. Sin embargo, esta deficiencia en la motilidad no tuvo consecuencias en la fertilidad de los ratones machos, demostrando ser tan fértiles como los WT. Finalmente, el abatimiento de AZIN2 en el aparato reproductor masculino se asoció a una disminución en la biosíntesis y la secreción de testosterona. 3. Expresión y función de AZIN2 en otros tejidos y células secretoras. Análisis fenotípico de los ratones KO de AZIN2. El papel de AZIN2 en la fisiología murina en otros tejidos que expresan AZIN2 se analizó comparando los cambios sobre la función en ratones KO de AZIN. En el cerebro de ratón, AZIN2 predomina en el cerebelo y en el hipocampo y su disrrupción en estas áreas está relacionada con un una función motora deficiente. La expression de AZIN2 en la glándula adrenal y el páncreas se limitó a la médula adrenal y a los islotes de Langerhans, respectivamente. En otros tejidos como corazón, ojos, pulmón y riñón, la expression de AZIN2 se concentró en tipos de células específicas. En páncreas, la ausencia de AZIN2 genera una ligera hiperglucemia porque afecta a la síntesis y secreción de insulina por las células β. 4. Propiedades estructurales y funcionales de Azin2 de Xenopus. El estudio de ODC en Xenopus reveló la existencia de dos proteínas homólogas denominadas XODC1 y XODC2, con diferente patró de expresión espacial y temporal. XODC2 aparece en las bancos de genes como XAZIN2, siendo considerado un ortólogo de mAZIN2 y hAZIN2. Al contrario que AZIN2 de ratón, su ortólogo en Xenopus (xlAZIN2) es degradado por AZ1 y presenta actividad descarboxilasa de ornitina y lisina, con una afinidad superior por lisina que por ornitina. El análisis comparativo de xlAZIN2 con mODC y mAZIN2 mostró una mayor semejanza con mODC, basándose en su localización subcelular citosólica y en la capacidad de ambas proteínas para formar oligómeros. Además, al igual que mODC, xlAZIN2 presenta una vida media muy corta (inferior a 30 minutos) y estimula la captación de agmatina en detrimento de la de putrescina y espermidina. 5. Estudio de Gm853, un nuevo parálogo de Odc y Azin2 en ratón. El análisis comparativo de la secuencia proteica de los distintos parálogos de ODC reveló la existencia de GM853, una nueva proteína homóloga de ODC y AZINs en ratón, que conserva todos los residuos relacionados con la actividad catalítica. Estudios con células transfectadas demostraron que GM853 no es un inhibidor de antizimas, ya que no evita la interacción entre ODC y AZ1. En cambio, es una proteína estable localizada fundamentalmente en el citosol y es capaz de formar homodímeros y homotetrámeros pero no heterodímeros con otros parálogos. GM853 presenta actividad enzimática, siendo la primera proteína descrita en mamíferos con actividad descarboxilasa de leucina. En ratón, GM853 se encuentra en el riñón y su expresión depende de los niveles de testosterona, predominando en el riñón de ratones machos. El producto de la descarboxilación de la leucina es la isopentilamina, una amina que es rápidamente eliminada a través de la orina.
Open Access
MGRN1 depletion promotes intercellular adhesion in melanoma by upregulation of E-cadherin and inhibition of CDC42.
(Elsevier, 2023-11-25) Abrisqueta, Marta; Sánchez-Beltrán, José; Muñoz, Cristina; Castejón Griñán, María; Cerdido Ochoa, Sonia; García-Borrón Martínez, José Carlos; Herraiz Serrano, Cecilia María; Jiménez-Cervantes Frigols, Celia; Lambertos Escudero, Ana; Olivares Sánchez, María Concepción; Bioquímica y Biología Molecular B e Inmunología
Open Access
Mahogunin Ring Finger 1 regulates pigmentation by controlling the pH of melanosomes in melanocytes and melanoma cells
(Springer Nature, 2021-12-18) Sirés-Campos, Julia; Delevoye, Cedric; Raposo, Graça; Bennett, Dorothy; Sviderskaya, Elena; Jiménez-Frigols, Celia; García-Borrón Martínez, José Carlos; Lambertos Escudero, Ana; Olivares Sánchez, María Concepción; Bioquímica y Biología Molecular B e Inmunología
Mahogunin Ring Finger 1 (MGRN1) is an E3-ubiquitin ligase absent in dark-furred mahoganoid mice. We investigated the mechanisms of hyperpigmentation in Mgrn1-null melan-md1 melanocytes, Mgrn1-KO cells obtained by CRISPR-Cas9-mediated knockdown of Mgrn1 in melan-a6 melanocytes, and melan-a6 cells depleted of MGRN1 by siRNA treatment. Mgrn1-deficient melanocytes showed higher melanin content associated with increased melanosome abundance and higher fraction of melanosomes in highly melanized maturation stages III-IV. Expression, post-translational processing and enzymatic activity of the rate-limiting melanogenic enzyme tyrosinase measured in cell-free extracts were comparable in control and MGRN1-depleted cells. However, tyrosinase activity measured in situ in live cells and expression of genes associated with regulation of pH increased upon MGRN1 repression. Using pH-sensitive fluorescent probes, we found that downregulation of MGRN1 expression in melanocytes and melanoma cells increased the pH of acidic organelles, including melanosomes, strongly suggesting a previously unknown role of MGRN1 in the regulation of melanosomal pH. Among the pH regulatory genes upregulated by Mgrn1 knockdown, we identified those encoding several subunits of the vacuolar adenosine triphosphatase V-ATPase (mostly Atp6v0d2) and a calcium channel of the transient receptor potential channel family, Mucolipin 3 (Mcoln3). Manipulation of expression of the Mcoln3 gene showed that overexpression of Mcoln3 played a significant role in neutralization of the pH of acidic organelles and activation of tyrosinase in MGRN1-depleted cells. Therefore, lack of MGRN1 led to cell-autonomous stimulation of pigment production in melanocytes mostly by increasing tyrosinase specific activity through neutralization of the melanosomal pH in a MCOLN3-dependent manner.
Open Access
Antizyme Inhibitor 2-Deficient Mice Exhibit Altered Brain Polyamine Levels and Reduced Locomotor Activity
(MDPI, 2023-12-21) Nuñez Sánchez, María Ángeles; López García, Carlos; López Contreras, Andrés Joaquín; Ramos-Molina, Bruno; Peñafiel, Rafael; Lambertos Escudero, Ana; Bioquímica y Biología Molecular B e Inmunología
Alterations in the neural polyamine system are known to be associated with different brain pathological conditions. In addition, the regulation of enzymes involved in polyamine metabolism such as ornithine decarboxylase (ODC), antizymes (AZs), and antizyme inhibitors (AZINs) is critical during brain development. However, while most studies focus on ODC and AZs, less is known about AZIN expression and function in the brain. Thus, our aim was to analyze the expression pattern of AZIN2 during postnatal development, its brain distribution, and its possible implication in phenotypical alterations. Methods: The expression pattern of Azin2 and other genes related to polyamine metabolism was analyzed by RT-qPCR. beta-D-galactosidase staining was used to determine the anatomical distribution of AZIN2 in a Azin2 knockout model containing the beta Geo marker. Brain polyamine content was determined by HPLC. The Rota-Rod and Pole functional tests were used to evaluate motor skills in Azin2-lacking mice. Results: Our results showed that expression of genes codifying for AZs and AZINs showed a similar increasing pattern over time that coincided with a decrease in ODC activity and putrescine levels. The analysis of AZIN2 distribution demonstrated that it is strongly expressed in the cerebellum and distributed along the neuron body and dendrites. The ablation of Azin2 showed a decrease in putrescine levels and is related to reduced motor skills. Conclusions: Our study revealed that AZIN2 expression in the brain is particularly limited to the cerebellum. In addition, the ablation of Azin2 leads to a reduction in putrescine that relates to alterations in motor function, suggesting the role of AZIN2 in the functioning of dopaminergic neurons.
Open Access
Melanoma-associated melanocortin 1 receptor variants confer redox signaling-dependent protection against oxidative DNA damage.
(Elsevier, 2024-03-26) Sánchez-Beltrán, José; Abrisqueta, Marta; Castejón Griñán, María; Cerdido Ochoa, Sonia; García-Borrón Martínez, José Carlos; Herraiz Serrano, Cecilia María; Jiménez-Cervantes Frigols, Celia; Lambertos Escudero, Ana; Bioquímica y Biología Molecular B e Inmunología
Cutaneous melanoma, a lethal skin cancer, arises from malignant transformation of melanocytes. Solar ultraviolet radiation (UVR) is a major environmental risk factor for melanoma since its interaction with the skin generates DNA damage, either directly or indirectly via oxidative stress. Pheomelanin pigments exacerbate oxidative stress in melanocytes by UVR-dependent and independent mechanisms. Thus, oxidative stress is considered to contribute to melanomagenesis, particularly in people with pheomelanic pigmentation. The melanocortin 1 receptor gene (MC1R) is a major melanoma susceptibility gene. Frequent MC1R variants (varMC1R) associated with fair skin and red or yellow hair color display hypomorphic signaling to the cAMP pathway and are associated with higher melanoma risk. This association is thought to be due to production of photosensitizing pheomelanins as well as deficient induction of DNA damage repair downstream of varMC1R. However, the data on modulation of oxidative DNA damage repair by MC1R remain scarce. We recently demonstrated that varMC1R accelerates clearance of reactive oxygen species (ROS)-induced DNA strand breaks in an AKT-dependent manner. Here we show that varMC1R also protects against ROS-dependent formation of 8- oxodG, the most frequent oxidative DNA lesion. Since the base excision repair (BER) pathway mediates clearance of these DNA lesions, we analyzed induction of BER enzymes in human melanoma cells of varMC1R genotype. Agonist-mediated activation of both wildtype (wtMC1R) and varMC1R significantly induced OGG and APE-1/Ref1, the rate-limiting BER enzymes responsible for repair of 8-oxodG. Moreover, we found that NADPH oxidase (NOX)-dependent generation of ROS was responsible for AKT activation and oxidative DNA damage repair downstream of varMC1R. These observations provide a better understanding of the functional properties of melanoma-associated MC1R alleles and may be useful for the rational development of strategies to correct defective varMC1R responses for efficient photoprotection and melanoma prevention in fair-skinned individuals.
Open Access
A Side-by-Side comparison of wildtype and variant melanocortin 1 receptor signaling with emphasis on protection against oxidative damage to DNA.
(MDPI, 2023-09-21) Sánchez-Beltrán, José; Abrisqueta, Marta; Padilla, Lidia; Herraiz Serrano, Cecilia María; Cerdido Ochoa, Sonia; García-Borrón Martínez, José Carlos; Herraiz Serrano, Cecilia María; Jiménez-Cervantes Frigols, Celia; Lambertos Escudero, Ana; Olivares Sánchez, María Concepción; Bioquímica y Biología Molecular B e Inmunología
Common variants of the MC1R gene coding the α-melanocyte stimulating hormone receptor are associated with light skin, poor tanning, blond or red hair, and increased melanoma risk, due to pigment-dependent and -independent effects. This complex phenotype is usually attributed to impaired activation of cAMP signaling. However, several MC1R variants show significant residual coupling to cAMP and efficiently activate mitogenic extracellular signal-regulated kinase 1 and 2 (ERK1/2) signaling. Yet, residual signaling and the key actions of wildtype and variant MC1R have never been assessed under strictly comparable conditions in melanocytic cells of identical genetic background. We devised a strategy based on CRISPR-Cas9 knockout of endogenous MC1R in a human melanoma cell line wildtype for BRAF, NRAS and NF1, followed by reconstitution with epitope-labeled MC1R constructs, and functional analysis of clones expressing comparable levels of wildtype, R151C or D294H MC1R. The proliferation rate, shape, adhesion, motility and sensitivity to oxidative DNA damage were compared. The R151C and D294H RHC variants displayed impaired cAMP signaling, intracellular stability similar to the wildtype, triggered ERK1/2 activation as effectively as the wildtype, and afforded partial protection against oxidative DNA damage, although less efficiently than the wildtype. Therefore, common melanoma-associated MC1R variants display biased signaling and significant genoprotective activity.
Open Access
MGRN1 as a phenotypic determinant of human melanoma cells and a potential biomarker.
(MDPI, 2022-07-26) Abrisqueta, Marta; Sánchez-Beltrán, José; Martínez-Vicente, Idoya; Sevilla, Arrate; Alonso, Santos; Boyano, María Dolores; Cerdido Ochoa, Sonia; García-Borrón Martínez, José Carlos; Herraiz Serrano, Cecilia María; Jiménez-Cervantes Frigols, Celia; Lambertos Escudero, Ana; Olivares Sánchez, María Concepción; Bioquímica y Biología Molecular B e Inmunología
Mahogunin Ring Finger 1 (MGRN1), a ubiquitin ligase expressed in melanocytes, interacts with the α melanocyte-stimulating hormone receptor, a well-known melanoma susceptibility gene. Previous studies showed that MGRN1 modulates the phenotype of mouse melanocytes and melanoma cells, with effects on pigmentation, shape, and motility. Moreover, MGRN1 knockdown augmented the burden of DNA breaks in mouse cells, indicating that loss of MGRN1 promoted genomic instability. However, data concerning the roles of MGRN1 in human melanoma cells remain scarce. We analyzed MGRN1 knockdown in human melanoma cells. Transient MGRN1 depletion with siRNA or permanent knockdown in human melanoma cells by CRISPR/Cas9 caused an apparently MITF-independent switch to a more dendritic phenotype. Lack of MGRN1 also increased the fraction of human cells in the S phase of the cell cycle and the burden of DNA breaks but did not significantly impair proliferation. Moreover, in silico analysis of publicly available melanoma datasets and estimation of MGRN1 in a cohort of clinical specimens provided preliminary evidence that MGRN1 expression is higher in human melanomas than in normal skin or nevi and pointed to an inverse correlation of MGRN1 expression in human melanoma with patient survival, thus suggesting potential use of MGRN1 as a melanoma biomarker.
Open Access
Polyamine biosynthesis in Xenopus laevis: the xlAZIN2/xlODC2 gene encodes a lysine/ornithine decarboxylase
(2019-09-11) Peñafiel, Rafael; Lambertos Escudero, Ana; Bioquímica y Biología Molecular B e Inmunología
Ornithine decarboxylase (ODC) is a key enzyme in the biosynthesis of polyamines, organic cations that are implicated in many cellular processes. The enzyme is regulated at the post-translational level by an unusual system that includes antizymes (AZs) and antizyme inhibitors (AZINs). Most studies on this complex regulatory mechanism have been focused on human and rodent cells, showing that AZINs (AZIN1 and AZIN2) are homologues of ODC but devoid of enzymatic activity. Little is known about Xenopus ODC and its paralogues, in spite of the relevance of Xenopus as a model organism for biomedical research. We have used the information existing in different genomic databases to compare the functional properties of the amphibian ODC1, AZIN1 and AZIN2/ODC2, by means of transient transfection experiments of HEK293T cells. Whereas the properties of xlODC1 and xlAZIN1 were similar to those reported for their mammalian orthologues, the former catalyzing the decarboxylation of L-ornithine preferentially to that of L-lysine, xlAZIN2/xlODC2 showed important differences with respect to human and mouse AZIN2. xlAZIN2 did not behave as an antizyme inhibitor, but it rather acts as an authentic decarboxylase forming cadaverine, due to its higher affinity to L-lysine than to L-ornithine as substrate; so, in accordance with this, it should be named as lysine decarboxylase (LDC) or lysine/ornithine decarboxylase (LODC). In addition, AZ1 stimulated the degradation of xlAZIN2 by the proteasome, but the removal of the 21 amino acid C-terminal tail, with a sequence quite different to that of mouse or human ODC, made the protein resistant to degradation. Collectively, our results indicate that in Xenopus there is only one antizyme inhibitor (xlAZIN1) and two decarboxylases, xlODC1 and xlLDC, with clear preferences for L-ornithine and L-lysine, respectively.
Open Access
Increased hepatic putrescine levels as a new potential factor related to the progression of metabolic dysfunction-associated steatotic liver disease.
(WILEY, 2024-07-18) Nuñez-Sanchez, Maria Ángeles; Martinez-Sanchez, María Antonia; Sierra-Cruz, Marta; Rico-Chazarra, Sara; Oliva-Bolarín, Alba; Balaguer-Román, Andrés; Yuste, José Enrique; Mika, Adriana; Frutos, María Dolores; Ramos-Molina, Bruno; Martínez Cáceres, Carlos Manuel; Lambertos Escudero, Ana; Bioquímica y Biología Molecular B e Inmunología
Metabolic dysfunction-associated steatotic liver disease (MASLD) is a chronic liver condition that often progresses to more advanced stages, such as metabolic dysfunction-associated steatohepatitis (MASH). MASH is characterized by inflammation and hepatocellular ballooning, in addition to hepatic steatosis. Despite the relatively high incidence of MASH in the population and its potential detrimental effects on human health, this liver disease is still not fully understood from a pathophysiological perspective. Deregulation of polyamine levels has been detected in various pathological conditions, including neurodegenerative diseases, inflammation, and cancer. However, the role of the polyamine pathway in chronic liver disorders such as MASLD has not been explored. In this study, we measured the expression of liver ornithine decarboxylase (ODC1), the rate-limiting enzyme responsible for the production of putrescine, and the hepatic levels of putrescine, in a preclinical model of MASH as well as in liver biopsies of patients with obesity undergoing bariatric surgery. Our findings reveal that expression of ODC1 and the levels of putrescine, but not spermidine nor spermine, are elevated in hepatic tissue of both diet-induced MASH mice and patients with biopsy-proven MASH compared with control mice and patients without MASH, respectively. Furthermore, we found that the levels of putrescine were positively associated with higher aspartate aminotransferase concentrations in serum and an increased SAF score (steatosis, activity, fibrosis). Additionally, in in vitro assays using human HepG2 cells, we demonstrate that elevated levels of putrescine exacerbate the cellular response to palmitic acid, leading to decreased cell viability and increased release of CK-18. Our results support an association between the expression of ODC1 and the progression of MASLD, which could have translational relevance in understanding the onset of this disease. (c) 2024 The Pathological Society of Great Britain and Ireland.