ABSTRACT Background: in advanced stages of non-small cell lung cancer, treatment is fundamentally based on polychemotherapy. Previous studies relate the development of resistance to cisplatin with increased levels of cellular glutathione, while depletion of this tripeptide has been associated with greater sensitivity to this drug. Objective: to evaluate the effect of polychemotherapy with cisplatin and vinblastine on intracellular glutathione levels and cellular redox status in patients with non-small cell lung cancer in advanced stages. Methods: a case-control study was carried out that included 38 patients with non-small cell lung cancer in stages IIIb-IV, who completed the treatment scheme with cisplatin and vinblastine, and 25 apparently healthy individuals as a control group from May 2016 to May 2018 at the Benéfico Jurídico Pneumological Hospital in Havana. The intraerythrocyte concentrations of reduced and oxidized glutathione were determined by an HPLC-UV method. The cellular redox state was calculated using the Nerst equation. The results were expressed as means and standard deviation. The non-parametric U-Mann Whitney test was used to compare the arithmetic means of the response variables. Results: after treatment, a decrease in reduced glutathione concentrations (920 µM vs. 1252 µM; p=0.036) was observed, as well as changes in the cellular redox state (-338.4 mV vs.-53.2 mV; p=0.029) in contrast to controls. Conclusions: chemotherapy combined with cisplatin induces a decrease in reduced glutathione levels and changes in the cellular redox state. These effects may contribute to increased survival in patients who respond to treatment.

RESUMEN Fundamento: en estadios avanzados del cáncer de pulmón de células no pequeñas el tratamiento se basa fundamentalmente en la poliquimioterapia. Estudios previos relacionan el desarrollo de resistencia al cisplatino con el aumento de los niveles del glutatión celular, mientras que, la depleción de este tripéptido se ha asociado con una mayor sensibilidad a este fármaco. Objetivo: evaluar el efecto de la poliquimioterapia con cisplatino y vinblastina en los niveles intracelulares de glutatión y en el estado redox celular en pacientes con cáncer de pulmón de células no pequeñas en estadios avanzados. Métodos: se realizó un estudio de casos y controles en el que se incluyeron 38 pacientes con cáncer de pulmón de células no pequeñas en estadios IIIb-IV, que concluyeron el esquema de tratamiento con cisplatino y vinblastina y 25 individuos aparentemente sanos como grupo control en el período correspondiente al período de mayo del 2016 a mayo del 2018 en el Hospital Neumológico Benéfico Jurídico de la Habana. Las concentraciones intraeritrocitarias del glutatión reducido y oxidado fueron determinadas mediante un método de HPLC-UV. El estado redox celular se calculó mediante la ecuación de Nerst. Los resultados se expresaron como medias y desviación estándar. Se utilizó la prueba no paramétrica U-Mann Whitney para la comparación de las medias aritméticas de las variables de respuesta. Resultados: después del tratamiento se apreció una disminución de las concentraciones de glutatión reducido (920 µM vs. 1252 µM; p=0,036) así como, cambios en el estado redox celular (-338,4 mV vs. -353,2 mV; p=0,029) en contraste con los controles. Conclusiones: la quimioterapia combinada con cisplatino induce una disminución de los niveles glutatión reducido y cambios en el estado redox celular. Estos efectos pueden contribuir a una mayor supervivencia en los pacientes que responden al tratamiento.

INTRODUCTION Hyperphenylalaninemias are inborn errors of phenylalanine metabolism caused by deficiency of L-phenylalanine hydroxylase (the enzyme that converts phenylalanine to tyrosine), resulting in increased serum phenylalanine (>4 mg/dL or 240 μmol/L). Phenylketonuria, or PKU, is the most common form. Untreated PKU is associated with progressive neurodevelopmental delay, evolving towards intellectual impairment. Cuba introduced a national newborn screening program for PKU in 1986. It has enabled early diagnosis and initiation of dietary treatment, reducing appearance of intellectual impairment in these patients. Originally, confirmatory diagnosis was done only by quantifying serum phenylalanine. In 2010, however, an HPLC method for quantifying serum phenylalanine and tyrosine simultaneously was validated at the National Medical Genetics Center, to perform confirmatory and differential diagnosis of hyperphenylalaninemias, as well as biochemical monitoring of patients diagnosed. OBJECTIVES Describe experience using HPLC confirmatory diagnosis for positive cases from the National Neonatal Screening Program for Phenylketonuria and in biochemical monitoring of diagnosed patients after initiation of dietary treatment. METHODS A descriptive retrospective case-series study was conducted from June 2010 through June 2012. The study population comprised 531 infants who tested positive in the National Neonatal Screening Program for Phenylketonuria. Variables used were serum phenylalanine concentration (first criterion of positivity) and tyrosine, phenylalanine/tyrosine ratio (second criterion, both detected by reverse-phase HPLC with direct fluorescence), hyperphenylalaninemia classification, year of diagnosis, sex, and province of origin. RESULTS Of the samples, 97.7% (519/531) were confirmed as false positives, and 10.4% (55/531) had transient neonatal tyrosinemia. Hyperphenylalaninemia was diagnosed in 12 infants (2.2%): 1.3% (7/531) presented classical PKU, with 34.7 ± 14.7 mg/dL phenylalanine in serum and phenylalanine/tyrosine ratio of 18.9 ± 12.7; and 0.9% (5/531) had persistent hyperphenylalaninemia, with 8.9 ± 3.4 mg/dL of phenylalanine and phenylalanine/tyrosine ratio of 4.5 ± 1.6. Matanzas Province contributed more cases than any of Cuba's 14 other provinces (3/12, 25%) and there was a slight predominance of male sex (7/12, 58.3%). During biochemical monitoring, 83.3% of patients (10/12) reduced their levels of phenylalanine (<5 mg/dL or 300 μmol/L): 5 with classical PKU and all 5 with persistent hyperphenylalaninemia. The incidence of neonatal hyperphenylalaninemias was 1/22,503 live births and 1/38,577 for classical PKU. CONCLUSIONS HPLC for simultaneous quantification of phenylalanine and tyrosine in serum meets the needs of a confirmatory test for patients testing positive in Cuba's National Neonatal Screening Program for Phenylketonuria (which has high false positive rates). It has enabled introduction in Cuba of a second PKU diagnostic criterion of positivity for both the classification of hyperphenylalaninemias and the biochemical monitoring of diagnosed patients.

Inborn purine metabolism errors are complex inherited disorders of great clinical impact that present with variable symptoms according to the type of disease. It might occur renal problems of unknown origin, metal retardation with neurological manifestations, retarded growth, recurrent infections, self-mutilation, immunodeficiencies, unexplainable haemolytic anemia, gout-related arthritis, family history, consanguinity and adverse reactions to those drugs that are analogous of purines. The study of these diseases generally begins by quantifying serum uric acid and uric acid present in the urine which is the final product of purine metabolism in human beings. Diet and drug consumption are among the pathological, physiological and clinical conditions capable of changing the level of this compound. This review was intended to disseminate information on the inborn purine metabolism errors as well as to facilitate the interpretation of the uric acid levels and other biochemical markers making the diagnosis of these diseases possible. The tables relating these diseases to the excretory levels of uric acid and other biochemical markers, the altered enzymes, the clinical symptoms, the model of inheritance, and in some cases, the suggested treatment. This paper allowed us to affirm that variations in the uric acid levels and the presence of other biochemical markers in urine are important tools in screening some inborn purine metabolism errors, and also other related pathological conditions.

Los errores innatos en el metabolismo de las purinas son trastornos hereditarios complejos de gran impacto clínico, que presentan síntomas variables de acuerdo con el tipo de enfermedad. Pueden presentarse problemas renales de origen desconocido, retardo mental con manifestaciones neurológicas, retardo del crecimiento, infecciones recurrentes, automutilación, inmunodeficiencias, anemia hemolítica inexplicable, artritis gotosa, historia familiar, consanguinidad y reacciones adversas a fármacos que son análogos de las purinas. Las investigaciones de estas enfermedades comienzan generalmente con la cuantificación del ácido úrico en suero y en orina, por ser el producto final del metabolismo de las purinas en humanos. La dieta y el consumo de medicamentos, entre otras condiciones patológicas, fisiológicas y clínicas, también pueden modificar los niveles de este compuesto. Esta revisión pretende divulgar información de los errores innatos en el metabolismo de las purinas, y facilitar la interpretación de los niveles del ácido úrico y otros marcadores bioquímicos útiles en el diagnóstico de estas enfermedades. Se incluyen tablas que relacionan estas enfermedades con los niveles de excreción de ácido úrico y otros marcadores bioquímicos, las enzimas alteradas, los síntomas clínicos, el modo de herencia y, en algunos casos, el tratamiento propuesto. Este trabajo nos permite afirmar que las variaciones en los niveles del ácido úrico y la presencia de otros marcadores bioquímicos en orina, constituyen una herramienta importante en la pesquisa de algunos errores innatos en el metabolismo de las purinas, así como de otras condiciones patológicas relacionadas.