Fadogia agrestis (Schweinf. Ex Hiern) Stem Extract Restores Selected Biomolecules of Erectile Dysfunction in the Testicular and Penile Tissues of Paroxetine-Treated Wistar Rats.

Inadequate release of nitric oxide (NO) by the penile tissue impacts negatively on penile erection causing erectile dysfunction (ED). Fadogia agrestis has been implicated in the management of ED without information on key biomolecules associated with ED in male rats. Therefore, this study evaluated the influence of aqueous extract of Fadogia agrestis stem (AEFAS) on key biomolecules associated with ED in the penile and testicular tissues of male Wistar rats induced with ED by paroxetine. Thirty male rats were assigned into 6 groups (I, II, III, IV, V and VI) of 5. Group I (sham control, without ED) was administered distilled water orally. Paroxetine-induced ED rats in groups II (negative control), III (positive control), IV, V and VI received distilled water, sildenafil citrate (SC, 50 mg/kg body weight) and AEFAS at 18, 50 and 100 mg/kg body weight respectively. Paroxetine lowered/reduced (p < 0.05) the MF, IF, EF, NO, cGMP, catalase, SOD, T-SH, GSH and GST whilst it prolonged/increased ML, IL, EL, PEI, AChE, PDE5, arginase, ACE, TBARS and H2O2. Contrastingly, AEFAS like sildenafil citrate increased (p < 0.05) the penile and testicular NO, cGMP, catalase, SOD, T-SH, GSH and GST and reduced AChE, PDE5, arginase, ACE, TBARS and H2O2 to levels that compared favourably (p > 0.05) with those of sham control. The study concluded that AEFAS restored the NO/cGMP pathway and ED-associated key enzymes in the penile and testicular tissues of male rats via antioxidant means. The study recommended the use of aqueous extract of Fadogia agrestis stem in managing ED after clinical trials.

Rescue of the Functional Alterations of Motor Cortical Circuits in Arginase Deficiency by Neonatal Gene Therapy.

UNLABELLED: Arginase 1 deficiency is a urea cycle disorder associated with hyperargininemia, spastic diplegia, loss of ambulation, intellectual disability, and seizures. To gain insight on how loss of arginase expression affects the excitability and synaptic connectivity of the cortical neurons in the developing brain, we used anatomical, ultrastructural, and electrophysiological techniques to determine how single-copy and double-copy arginase deletion affects cortical circuits in mice. We find that the loss of arginase 1 expression results in decreased dendritic complexity, decreased excitatory and inhibitory synapse numbers, decreased intrinsic excitability, and altered synaptic transmission in layer 5 motor cortical neurons. Hepatic arginase 1 gene therapy using adeno-associated virus rescued nearly all these abnormalities when administered to neonatal homozygous knock-out animals. Therefore, gene therapeutic strategies can reverse physiological and anatomical markers of arginase 1 deficiency and therefore may be of therapeutic benefit for the neurological disabilities in this syndrome. SIGNIFICANCE STATEMENT: These studies are one of the few investigations to try to understand the underlying neurological dysfunction that occurs in urea cycle disorders and the only to examine arginase deficiency. We have demonstrated by multiple modalities that, in murine layer 5 cortical neurons, a gradation of abnormalities exists based on the functional copy number of arginase: intrinsic excitability is altered, there is decreased density in asymmetrical and perisomatic synapses, and analysis of the dendritic complexity is lowest in the homozygous knock-out. With neonatal administration of adeno-associated virus expressing arginase, there is near-total recovery of the abnormalities in neurons and cortical circuits, supporting the concept that neonatal gene therapy may prevent the functional abnormalities that occur in arginase deficiency.

Molecular basis and current strategies of therapeutic arginine depletion for cancer.

Renewed interest in the use of therapeutic enzymes combined with an improved knowledge of cancer cell metabolism, has led to the translation of several arginine depletion strategies into early phase clinical trials. Arginine auxotrophic tumors are reliant on extracellular arginine, due to the downregulation of arginosuccinate synthetase or ornithine transcarbamylase-key enzymes for intracellular arginine recycling. Engineered arginine catabolic enzymes such as recombinant human arginase (rh-Arg1-PEG) and arginine deiminase (ADI-PEG) have demonstrated cytotoxicity against arginine auxotrophic tumors. In this review, we discuss the molecular events triggered by extracellular arginine depletion that contribute to tumor cell death.

In-vivo evaluation of human recombinant Co-arginase against A375 melanoma xenografts.

Metastatic melanoma is a deadly form of cancer with few therapeutic options and the cause of more than 9480 deaths annually in the USA alone. Novel treatment options for this disease are urgently needed. Here we test the efficacy of a novel melanoma drug, the human recombinant Co-arginase (CoArgIPEG), against an aggressive A375 melanoma mouse model. CoArgIPEG is a modification of the naturally occurring human enzyme with improved stability, catalytic activity, and potentially lower immunogenicity compared with current amino acid-depleting drugs. Marked tumor growth reductions (mean P=0.0057) with apoptosis induction and proliferation inhibition are noted with CoArgIPEG treatment, both in the presence and in the absence of supplemental citrulline. Further, improved therapeutic efficacy has been noted against A375 xenografts relative to the naturally occurring human recombinant arginase enzyme at lower doses of CoArgIPEG. Unfortunately, after 1 month, half of the relapsing tumors showed argininosuccinate synthase induction, which correlated with Ser62-phosphorylated cMyc. Although argininosuccinate synthase induction could not be induced in vitro, a drug targeting pathway previously demonstrated to be associated with Ser62 cMyc phosphorylation - U0126 - in combination with CoArgIPEG demonstrated an in-vitro synergistic response (combination indices 0.13±0.10 and 0.14±0.10 with or without citrulline, respectively). Overall, favorable efficacy and potential synergy with other antimelanoma drugs support CoArgIPEG as a potent, novel cancer therapeutic.

Recombinant human arginase inhibits proliferation of human hepatocellular carcinoma by inducing cell cycle arrest.

Human hepatocellular carcinoma (HCC) has an elevated requirement for arginine in vitro, and pegylated recombinant human arginase I (rhArg-PEG), an arginine-depleting enzyme, can inhibit the growth of arginine-dependent tumors. While supplementation of the culture medium with ornithine failed to rescue Hep3B cells from growth inhibition induced by rhArg-PEG, citrulline successfully restored cell growth. The data support the roles previously proposed for ornithine transcarbamylase (OTC) in the arginine auxotrophy and rhArg-PEG sensitivity of HCC cells. Expression profiling of argininosuccinate synthetase (ASS), argininosuccinate lyase (ASL) and OTC in 40 HCC tumor biopsy specimens predicted that 16 of the patients would be rhArg-sensitive, compared with 5 who would be sensitive to arginine deiminase (ADI), another arginine-depleting enzyme with anti-tumor activity. Furthermore, rhArg-PEG-mediated deprivation of arginine from the culture medium of different HCC cell lines produced cell cycle arrests at the G(2)/M or S phase, possibly mediated by transcriptional modulation of cyclins and/or cyclin dependent kinases (CDKs). Based on these results, together with further validation of the in vivo efficacy of rhArg-PEG against HCC, we propose that the application of rhArg-PEG alone or in combination with existing chemotherapeutic drugs may represent a specific and effective therapeutic strategy against HCC.

Purification, modification, physico-chemical and pharmacokinetic characterization of arginase, an enzyme of potential use in therapy.

Beef liver arginase, an enzyme potentially useful in the therapy of arginine dependent tumors or of familial hyperargininemia, was purified to homogeneity by a procedure involving a key step of hydrophobic affinity chromatography. The enzyme was extensively modified by the covalent linking of monomethoxypolyethyleneglycol molecules according to a procedure recently proposed by the Authors (Veronese et al., Appl. Biochem. Biotecnol. 11, 869, 1985) without any significant loss of activity. The derivative enzyme presents more convenient properties for a therapeutic use, as compared to the native enzyme, such an increased structural stability, a decreased digestion by proteolytic enzymes and an expanded clearance time in rats.

A successful trial of enzyme replacement therapy in a case of argininemia.

A 5-year-old boy with severe mental retardation and spastic quadriplegia accompanied by tonic seizures and hyperammonemia was diagnosed as having argininemia due to an arginase deficiency in his erythrocytes. His motor and mental abilities began to deteriorate at the age of 3 years. Thereafter, he lost his ability to stand alone, to sit and even to crawl by himself. After he was diagnosed as argininemia , a protein restricted diet was given as therapy, which was accompanied with a supplement of essential amino acids. However, his clinical condition had not improved very much. The erythrocytes in a normal person was found to have the ability to decrease the patient's elevated plasma arginine level to normal when they are mixed in vitro. First we tried replacing his red cells by a blood transfusion. Then we replaced them with the aid of an IBM 2997 blood cell separator. Following this his clinical and biochemical condition improved, and as a result so did his sitting and crawling abilities. It appears that the replacement of red blood cells improves not only the clinical and biochemical conditions, but the general condition of the patient as well.

The significance of the arginine and arginase of tears in experimentally-induced herpes simplex corneae.

Experimental corneal herpes is always accompanied by the accumulation of arginine, the substrate of arginase, in tears, ensuring the multiplication of the herpes hominis virus. The main source of the large amount of arginine is the desquamating corneal epithelium, since after the epithelium of the cornea is abraded the arginine content of the tears again equals that of healthy tears. The low arginase content of rabbit tears can be supplemented by arginase applied as eyedrops, and this results in the cure of the herpetic process.