PPA Treatment Research Articles

Abstract 1410: An effect of Phenylalanine hydroxylase (PAH) deficiency on cancer development in kidney

Abstract Several studies have noted the importance of amino acid metabolism in cancer progression. Preliminary research using public cancer multi-omics data has revealed associations between heterozygous germline mutations in genes associated with amino acid metabolism and cancer development. In particular, the heterozygous status of the PAH gene enhances the risk of developing kidney cancer by more than three times. Phenylalanine hydroxylase (PAH) is an enzyme that converts phenylalanine to tyrosine. It is highly expressed in the liver and kidneys. Analysis of the blood metabolome in prospectively collected PAH heterozygous carriers indicates that heterozygous status causes metabolome fluctuations in the body. By the way, renal cell carcinoma (RCC) is an immunogenic tumor mainly infiltrated by T cells. Accordingly, we suggest that defects in the PAH gene change the metabolites in the body, leading to a reduction in immune function and an increased risk of developing kidney cancer. First, the expression of the PAH protein was confirmed through immunohistochemistry in a tissue microarray from RCC patients, and the results were then compared with clinical information. Next, we simulated the environment of PAH deficiency in vitro by treating the cells with phenylalanine (Phe) and its metabolite, phenylpyruvate (PRA), which accumulates during PAH dysfunction. The cytotoxicity of Phe and PPA was investigated using the WST assay. The Jurkat T cell line was cultured long-term in a medium containing Phe or PPA and then stimulated with PHA/PMA. Cytokine secretion was confirmed in these supernatants. In addition, purified primary human pan T cells were stimulated with Anti-CD3/CD28 in the medium containing either Phe or PPA. Proliferation was evaluated using CFSE staining. The IHC was performed on 467 tissues from RCC patients aged 29 to 101 years. We classified the cases into three scale scores based on the percentage of PAH intensity. Approximately 73% of cases were PAH-negative, and only 27% were positive (score 1+ or 2+). A comparison of IHC results with clinical information showed that lower PAH expression was associated with a lower relapse-free survival rate. Next, Phe and PPA exhibited minimal cytotoxicity. The secretion of representative proinflammatory cytokines IL-2 and TNF- α were dose-dependent and significantly decreased with Phe and PPA treatment. Additionally, cell proliferation, a critical step in acquiring effector functions of T cells, was inhibited by treatment with Phe and PPA, particularly in the CD8+ T cell population compared to CD4+ T cells. These results suggest that metabolite changes within the tissue microenvironment of the kidney, caused by Pah defects, may suppress anti-tumor immunity by impairing the function of immune cells. This novel discovery may contribute to the importance of the PAH gene as a new biomarker for diagnosing kidney cancer and to the development of kidney cancer therapy. Citation Format: Seojeong Kim, Jihyun Park, Jeongmin Park, Chaelin Kang, Kyung Chul Moon, Seung Seok Han, Youngil Koh, Sung-Soo Yoon. An effect of Phenylalanine hydroxylase (PAH) deficiency on cancer development in kidney [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1410.

Analysis of endogenous hormones in different organs reveals the critical role of phthalanilic acid in the yield and quality of pepper (Capsicum annuum) fruits

Phthalanilic acid (PPA), a plant growth regulator, has advantageous biological effects on fruit trees. However, little is known about its effects on vegetables. Thus, field trials were conducted on pepper (Capsicum annuum) plants by spraying with PPA at concentrations of 133.3, 200.0, and 266.7 mg·L−1. The key physiological indicators of peppers were investigated, including the number of flowers and fruits, yield, yield components, quality, and endogenous hormones. Results showed that PPA greatly boosted the number of flowers and fruits on pepper plants. The fruit shape index, dry matter content, single fruit weight, and yield in the PPA treatment of 133.3 mg·L−1 were particularly higher than those of the control, with increasing rates of 28.73%, 22.97%, 26.85%, and 35.75%, respectively. PPA considerably decreased the levels of titratable acid and nitrate while noticeably increasing the levels of soluble protein, soluble sugar, l-ascorbic acid, and capsaicin in mature green or red pepper fruits. PPA may also increase the levels of indole-3-acetic acid (IAA) in flowers, buds, and leaves, elevate the levels of abscisic acid (ABA) in leaves, raise the levels of zeatin riboside (ZR) in young fruits, but decrease the ABA content in buds. PPA actively controls fruit quality and yield in the concentration range of 133.3–200.0 mg·L−1. This beneficial outcome might ultimately be connected to the regulation of endogenous hormones.

Peracetic Acid Treatment as an Effective Method to Protect Wood Discoloration by UV Light

Wood has always been used for various day-to-day applications such as interior or exterior construction materials, and household products. However, it can undergo photodegradation and discoloration by environmental factors including ultraviolet (UV) light, and thus has shortened its service life. Bleaching or delignification of wood surfaces is a suitable solution to stabilize wood against weathering by UV because these techniques can alter or remove the chromophores in lignin, which is a main factor of wood discoloration. To improve the color stability of wood surface according to the lifespan, surface delignification was conducted using peracetic acid (PAA) and hydrogen peroxide (HP) on the woods of Larix kaempferi and Quercus mongolica. After the PAA treatment, L* increased considerably from 60–70 to 90–95. Furthermore, wood surface color did not change significantly after UV exposure. The color differences (ΔE*) between before and after PPA treatment of wood showed the 4.8–12.2 of L. kaempferi, and 1.7–3.7 of Q. mongolica, respectively. The lignin-related peaks in Fourier transform infrared spectroscopy (FT-IR) spectra disappeared with increased duration of PAA treatment. These results confirmed that the lignin component was partially or completely removed after the PAA treatment; the color differences (ΔE*) clearly showed that there was a reduction in redness (a*) and yellowness (b*), and an increase in lightness (L*) owing to the removal of lignin. Based on these results, this study demonstrated that the partial removal of lignin from wood surfaces is a fundamental method for resolving photo-degradation.

Mediation of oxidative stress in hypothalamic ghrelin-associated appetite control in rats treated with phenylpropanolamine

Phenylpropanolamine (PPA)-induced appetite control is associated with oxidative stress in the hypothalamus. This study explored whether hypothalamic antioxidants participated in hypothalamic ghrelin system-associated appetite control in PPA-treated rats. Rats were given PPA daily for 4 days, and changes in food intake and the expression of neuropeptide Y (NPY), the cocaine- and amphetamine-regulated transcript (CART), superoxide dismutase, catalase, ghrelin, acyl ghrelin (AG), ghrelin O-acyltransferase (GOAT) and the ghrelin receptor (GHSR1a) were examined and compared. Results showed that both food intake and the expression of NPY and ghrelin/AG/GOAT/GHSR1a decreased in response to PPA treatment with maximum decrease on Day 2 of the treatment. In contrast, the expression of antioxidants and CART increased, with the maximum increase on Day 2, with the expression opposite to that of NPY and ghrelin. A cerebral infusion of either a GHSR1a antagonist or reactive oxygen species scavenger modulated feeding behavior and NPY, CART, antioxidants and ghrelin system expression, showing the involvement of ghrelin signaling and oxidative stress in regulating PPA-mediated appetite control. We suggest that hypothalamic ghrelin signaling system, with the help of antioxidants, may participate in NPY/CART-mediated appetite control in PPA-treated rats.

Pathophysiological and Neurobehavioral Identification of Propionic Acid‐mediated Autism‐mimetic Rat Model

ASD is a heritable neurodevelopmental disorder with poorly understood and complex etiology. The purpose of this study is to construct autism mimetic animal models, and to establish how to create autism‐mimetic animal models and the standard indicators, through a comparison between the autism clinical aspects, pathophysiological and neurobehavioral alteration. 22 male SD rats were employed and randomly divided the control and propionic acid (500mg/kg) treated rats groups. The rats were subjected behavioral tests, gene expression, and histological analysis for pathophysiological and neurobehavioral alteration. PPA‐treated rats were significantly reduced exploring activity, non‐aggressive behaviors, whereas enhanced aggressive behavior (**p<0.01). Proinflammatory cytokine, TNF‐a was continuously upregulated PPA‐treated rats hippocampus following time‐dependent (**p<0.01). Expression of GFAP was significantly augmented at day 14 after PPA treatment (**p<0.01). In histological evaluation, PPA‐treated rats were significantly reduced diameter of granular cells and thickness of granular cell layer rather than control rats (**p<0.01). We suggest that PPA administration could induce a critical role of proinflammatory cytokine elevation and abnormal neural cells organization, which reveal autism‐mimic neurobehaviors, including increment of aggressive behavior, reduction of exploring activity, and exclusive and passive behavior.Funding: 2012R1A1A2005089, 2013R1A2A2A01067169, KGM4611512

Targeting oxidative stress in the hypothalamus: the effect of transcription factor STAT3 knockdown on endogenous antioxidants-mediated appetite control.

It has been reported that the redox sensing system in the hypothalamus participates in fuel metabolism and that endogenous antioxidants contribute to the regulation of phenylpropanolamine (PPA), an anorectic drug-induced appetite suppression. We explored whether the signal transducer and activator of transcription-3 (STAT3) is involved in PPA's action. Rats were given PPA once a day for 4 days. Changes in endogenous antioxidants, Janus kinase-2 (JAK2), STAT3, neuropeptide Y (NPY), and proopiomelanocortin (POMC), levels during PPA treatment were assessed and compared. Feeding, body weight, and NPY decreased with the biggest reduction on Day 2 during PPA treatment. Antioxidants, JAK2, pSTAT3, POMC expression, and STAT3/DNA-binding activity increased and were expressed in a pattern opposite to NPY expression. Moreover, cerebral STAT3 knockdown modified PPA-induced anorexia and antioxidants, POMC, and NPY expression. superoxide dismutase immunoreactivity in the hypothalamus increased and the inhibition of hypothalamic reactive oxygen species (ROS) production reversed antioxidants, STAT3, POMC, and NPY expression. It is suggested that hypothalamic JAK2-STAT3 participates in regulating antioxidants-mediated appetite control. This result may further the understanding of ROS-involved appetite control.

The Identification of Neuropeptide Y Receptor Subtype Involved in Phenylpropanolamine-induced Increase in Oxidative Stress and Appetite Suppression

Hypothalamic neuropeptide Y (NPY) and superoxide dismutase (SOD) have been reported to participate in the regulation of appetite-suppressing effect of phenylpropanolamine (PPA), a sympathomimetic agent. This study explored whether Y1 receptor (Y1R) and/or Y5 receptor (Y5R) was involved in this regulation. Wistar rats were treated with PPA for 24h. Changes in food intake and hypothalamic NPY, Y1R, Y5R, and SOD contents were assessed and compared. Results showed that food intake and NPY contents were decreased following PPA treatment, while Y1R and SOD contents were increased and Y5R contents remained unchanged. Moreover, although Y1R or Y5R knockdown by themselves could modify the food intake, Y1R but not Y5R knockdown could modify PPA-induced anorexia as well as NPY and SOD contents. In addition, selective inhibition of Y1R but not Y5R could modulate PPA-induced anorexia. It is suggested that Y1R but not Y5R participates in the anorectic response of PPA via the modulation of NPY and SOD. Results provide molecular mechanism of NPY-mediated PPA anorexia and may aid the understanding of the toxicology of PPA.

Neuropeptide Y Y1 receptor knockdown can modify glutathione peroxidase and c-AMP response element-binding protein in phenylpropanolamine-treated rats

It has been reported that antioxidative enzymes, neuropeptide Y (NPY), and c-AMP response element-binding protein (CREB) are involved in regulating phenylpropanolamine (PPA)-mediated appetite suppression. Here, we investigated whether Y1 receptor (Y1R) might be involved in this regulation. Rats were daily treated with PPA for 4days. Changes in the contents of NPY, Y1R, glutathione peroxidase (GP), and CREB were assessed and compared. Results showed that Y1R, GP, and CREB increased, with a maximal increase about 100, 200, and 150%, respectively, on Day 2. By contrast, NPY decreased with a biggest reduction about 48% on Day 2 and the pattern of expression during PPA treatment was opposite to those of Y1R, GP, and CREB. Central knockdown (using antisense) or inhibition (using antagonist) of Y1R expression modulated the anorectic response of PPA and the reciprocal regulation between NPY and GP (or CREB), revealing an essential role of Y1R in regulating NPY, GP, and CREB. These results suggest that Y1R participates in the reciprocal regulation of NPY, GP, and CREB in the hypothalamus during PPA treatment in conscious rats. The present results may aid the therapeutic research of PPA and related antiobesity drugs.

Evaluation of once daily dose of phenylpropanolamine in the treatment of urethral sphincter mechanism incompetence in spayed bitches

Summary: The aim of this study was to evaluate the efficacy and long term safety of once daily administration of phenylpropanolamine (PPA) in the treatment of urethral sphincter mechanism incompetence (USMI) in spayed bitches in comparison to three times daily administrations. For this purpose, 22 spayed bitches suffering from USMI received either PPA at the dose rate of 1.5 mg/kg, body weight (BW) once daily (group I, n=11) or 1.5 mg/kg three times daily (group II, n=11) by oral administration. Clinical efficacy was determined by using a scoring system based on analysing the frequency and the amount of unconscious urination on d 7, 14 and 28. There was no significant difference (p>0.05) between the clinical response observed on d 7, 14 and 28 of treatment in group I and II. Eight dogs (72.7%) in each group were continent on d 28. The side effects observed were mild and transient. Phenylpropanolamine therapy was continued in 13 dogs that became continent after 28 d and the dogs were followed up for 12 months. None of the dogs showed symptoms of urinary incontinence except for 2 bitches that became refractory to PPA treatment in group II. Phenylpropanolamine was combined with estriol for 14 d (1 mg/dog PO) in dogs in which PPA therapy was inefficient or unsatisfactory on d 28 and in dogs that became refractory to PPA treatment. A total of 8 dogs were treated with estriol PPA combination. Five (62.5%) bitches were continent on 14 th d of estriol PPA combination treatment. In one bitch (12.5%) urinary incontinence improved. In conclusion, once daily administration of PPA at a dose of 1.5 mg/kg, BW is effective in treatment of USMI in spayed bitches and it offers a cheap and convenient treatment option. In addition, recurrence of incontinence can be observed during long term administration of PPA and combination of PPA with estriol is effective in dogs in which PPA therapy alone is unsatisfactory and in dogs that become refractory to PPA treatment.

Knocking down the transcript of NF-kappaB modulates the reciprocal regulation of endogenous antioxidants and feeding behavior in phenylpropanolamine-treated rats

It has been reported that oxidative stress, antioxidants, and neuropeptide Y (NPY) are involved in regulating the feeding behavior of phenylpropanolamine (PPA), a sympathomimetic drug. This study explored whether transcription factor NF-κB is involved in this effect. Rats were treated daily with PPA for 4 days. Changes in hypothalamic NF-κB, NPY, superoxide dismutase (SOD), and glutathione peroxidase (GPx) levels during PPA treatment were assessed and compared. Results showed that NF-κB, SOD, and GPx increased, with a maximal response on Day 2, while the food intake and NPY decreased with the biggest reduction on Day 2 during PPA treatment. To further determine whether NF-κB was involved, intracerebroventricular infusion of antisense oligonucleotide was performed at 1 h before daily PPA in free-moving rats. Cerebral NF-κB knockdown could modify PPA anorexia and the expressions of NPY, SOD, and GPx. It is suggested that hypothalamic NF-κB participates in the reciprocal regulation of NPY and antioxidants, which mediated the appetite-suppressing effect of PPA. Results may further the understanding of the molecular mechanisms of PPA.

The effect of protein kinase C‐delta knockdown on anti‐free radical enzyme and neuropeptide Y gene expression in phenylpropanolamine‐treated rats

Hypothalamic neuropeptide Y (NPY) has been reported to involve in regulating behavioral response of phenylpropanolamine (PPA), a sympathomimetic agent. This study explored if protein kinase C (PKC)-delta signaling participated in this regulation. Moreover, possible roles of anti-free radical enzyme catalase (CAT) and nitrogen oxide synthase (NOS) were also examined. Rats were treated daily with PPA for 4 days. Changes in food intake and hypothalamic NPY, PKCdelta, CAT, and NOS contents were assessed and compared. Results showed that PKCdelta and CAT increased during PPA treatment, which were concomitant with decreases in NPY content and food intake, while the change of NOS was expressed differently. Moreover, PKCdelta knockdown could modify PPA anorexia as well as NPY and CAT expression, while NOS expression remained unchanged. Furthermore, pre-treatment with NOS inhibitor could modify both PPA anorexia and NPY content. It is suggested that PKCdelta participates in the anorectic response of PPA via the modulation of NPY and CAT, while NOS contribute to this modulation via a different mechanism during PPA treatment. Results provide molecular mechanism of NPY-mediated PPA anorexia and may aid the therapeutic research of PPA and other anti-obesity drugs.

Roles of protein kinase Cα isozyme in the regulation of oxidative stress and neuropeptide Y gene expression in phenylpropanolamine‐mediated appetite suppression

Hypothalamic neuropeptide Y (NPY) is an appetite stimulant in the brain. Although regulation of NPY expression has been reported to contribute to the appetite-suppressing effect of phenylpropanolamine (PPA), it is still unknown if protein kinase C (PKC) is involved in this effect. Rats were daily treated with PPA for 4 days. Changes in food intake, hypothalamic NPY, PKC, and proopiomelanocortin (POMC) mRNA levels were assessed and compared. Results showed that the NPY gene was down-regulated following PPA treatment, which was parallel with the decrease of feeding. Moreover, several isotypes of PKC mRNA level (alpha, betaI, betaII, gamma, delta, eta, lambda, epsilon, and zeta) were changed. Among these, alpha, delta, and lambda PKC were up-regulated along with POMC gene expression which coincided with down-regulation of the NPY gene. To further determine if PKCalpha was involved, infusions of antisense oligonucleotide into the cerebroventricle were performed at 1 h before daily PPA treatment in free-moving rats. Results showed that PKCalpha knock-down could modify both anorexia induced by PPA and the NPY mRNA levels. Moreover, PKCalpha knock-down could also modify superoxide dismutase (SOD) gene expression. It is suggested that PKCalpha participates in the regulation of PPA-mediated appetite suppression via the modulation of NPY and SOD gene expression.

PRECLINICAL STUDY: Protracted ‘anti‐addictive’ effects of adolescent phenylpropanolamine exposure in C57BL/6J mice

Exposure to the once highly prevalent over-the-counter (OTC) sympathomimetic phenylpropanolamine (PPA; +/--norephedrine) during pre-adolescence alters the developmental trajectory of catecholamine and amino acid neurotransmitter systems in the nucleus accumbens (NAC) that culminate in a 'pro-addictive' phenotype in adulthood. Thus, the present study sought to extend these earlier data by examining the long-term consequences of repeated PPA treatment during adolescence upon the behavioral and neurochemical responses to cocaine. For this, C57BL/6J mice were pre-treated with PPA (0-40 mg/kg) during postnatal days 35-44, and the capacity of cocaine (4 x 15 mg/kg) to elicit a conditioned place-preference, as well as behavioral and neurochemical sensitization within the NAC, were then assessed in adulthood. While adolescent PPA exposure did not influence spontaneous locomotor activity or the motor responses to either acute or repeated cocaine (4 x 15 mg/kg), PPA pre-exposure dose-dependently reduced the expression of a conditioned place-preference. As observed previously for juvenile PPA treatment, adolescent PPA administration blunted the dopamine and norepinephrine response to acute cocaine, prevented the development of catecholamine sensitization but did not influence cocaine-induced elevations in serotonin. However, unlike juvenile PPA treatment, adolescent PPA also prevented the development of glutamate sensitization within the NAC. These data provide evidence that adolescent exposure to a formerly prevalent OTC sympathomimetic produces protracted effects upon cocaine-induced changes in NAC glutamate transmission that may reduce vulnerability to cocaine addiction in later life and further the hypothesis that early exposure to sympathomimetic drugs may be an environmental factor contributing to the etiology of addiction.

Transcriptional interruption of cAMP response element binding protein modulates superoxide dismutase and neuropeptide Y‐mediated feeding behavior in freely moving rats

The appetite-suppressing effect of phenylpropanolamine (PPA) has been attributed to its inhibitory action on neuropeptide Y (NPY), an appetite stimulant. However, molecular mechanisms underlying this effect are not clear. This study aimed to investigate if cAMP response element binding protein (CREB) signaling was involved. Moreover, possible role of superoxide dismutase-2 (SOD-2) during PPA treatment was also examined. Rats were daily treated with PPA for 4 days. Changes in hypothalamic NPY, protein kinase A, CREB, and SOD-2 mRNA contents were measured and compared. Results showed that protein kinase A, CREB, and SOD-2 mRNA levels increased during PPA treatment, which is concomitant with decreases in NPY and feeding. Moreover, CREB DNA binding activity detected by electromobility shift assay increased during PPA treatment, revealing an involvement of CREB-dependent gene transcription. Furthermore, infusions of CREB antisense oligonucleotide (or missense control) into cerebroventricle were performed at 1 h before daily PPA treatment in free-moving rats, and results showed that CREB knockdown could block PPA-induced anorexia and modify NPY and SOD-2 mRNA content toward normal. It is suggested that CREB signaling may participate in the central regulation of PPA-mediated appetite suppression via the modulation of NPY gene expression and that an increase of SOD-2 may favor this modulation.

Interrupting activator protein‐1 signaling in conscious rats can modify neuropeptide Y gene expression and feeding behavior of phenylpropanolamine

The mechanism for phenylpropanolamine (PPA)-induced anorexia has been attributed to its inhibitory action on hypothalamic neuropeptide Y (NPY), an orexigenic agent abundant in the brain. However, molecular mechanisms behind this effect are not well known. In this study, we investigated whether activator protein-1 (AP-1) signaling was involved. Rats were daily treated with PPA for 4 days. Changes in hypothalamic NPY, c-fos, c-jun, superoxide dismutase (SOD)-1, and SOD-2 mRNA contents were measured and compared. Results showed that c-fos and c-jun mRNA levels were increased following PPA treatment, which were relevant to a reduction in NPY mRNA level. To further determine if c-fos/c-jun genes were involved in PPA anorexia, infusions of antisense oligonucleotide into cerebroventricle were performed before daily PPA treatment in freely moving rats. Results showed that either c-fos or c-jun knock down could block PPA anorexia and restore NPY mRNA content to normal level. It is suggested that AP-1 signaling may participate in the central regulation of PPA-mediated appetite suppression via the modulation of NPY gene expression. Moreover, this modulation might be partly because of the neuroprotective effect of AP-1 since SOD gene was activated during PPA treatment.

Transcript of protein kinase A knock-down modulates feeding behavior and neuropeptide Y gene expression in phenylpropanolamine-treated rats

Neuropeptide Y (NPY) is an appetite-controlling neuromodulator that contributes to the appetite-suppressing effect of phenylpropanolamine (PPA). Aims of this study were to investigate whether protein kinase A (PKA) signaling is involved in regulating NPY gene expression and PPA-induced anorexia. Rats were given daily with PPA for 5 days. Changes in daily food intake and hypothalamic NPY, PKA, cAMP response element binding protein (CREB), and pro-opiomelanocortin (POMC) gene expression were measured and compared. To further determine if PKA was involved, intracerebroventricular infusions of antisense oligodeoxynucleotide were performed at 60 min before daily PPA treatment in freely moving rats. Results showed that daily PKA, CREB, and POMC expression were increased following PPA treatment, which showed a closely reverse relationship with alterations of decreased feeding behaviors and NPY mRNA levels. Results also showed that PKA knock-down could block PPA-induced anorexia as well as restore NPY mRNA level, indicating the involvement of PKA signaling in the regulation of NPY gene expression. It is suggested that hypothalamic PKA signaling may participate in the central regulation of PPA-mediated appetite suppression via the modulation of hypothalamic NPY gene expression. The present findings reveal that manipulations at the molecular level of PKA or cAMP may allow the development of therapeutic agents to improve the undesirable properties of PPA or other amphetamine-like anorectic drugs.

Roles of central catecholamine and hypothalamic neuropeptide Y genome in the development of tolerance to phenylpropanolamine-mediated appetite suppression.

Phenylpropanolamine (PPA) is an appetite suppressant. Repeated treatment with PPA can decrease food intake on initial days, but on subsequent days, food intake gradually returns to normal (tolerant effect). In an attempt to investigate the underlying mechanisms of PPA tolerance, the authors examined the roles of catecholamine (CAT) and hypothalamic neuropeptide Y (NPY) genome. Results revealed that pretreatment with either bupropion, a CAT transporter inhibitor, or a-methylparatyrosine, a tyrosine hydroxylase inhibitor, modulated the effect of PPA tolerance. Moreover, results also revealed that the alteration in NPY messenger RNA level coincided with the change of feeding behavior during PPA treatment and that infusions of NPY antisense oligonucleotide into the cerebroventricle abolished the effect of PPA tolerance. These findings suggest that cerebral CAT and hypothalamic NPY genome are involved in the development of tolerance to PPA-induced appetite suppression.

Immunohistochemical and genomic evidence for the involvement of hypothalamic neuropeptide Y (NPY) in phenylpropranolamine-mediated appetite suppression

Phenylpropanolamine (PPA) is an appetite suppressant. The mechanism for the anorectic effect of PPA has been attributed to its action on the site of hypothalamic paraventriculum. Neuropeptide Y (NPY) is an appetite stimulant that is widely distributed in the site of hypothalamus. It is not clear whether hypothalamic NPY is involved in the anorectic action of PPA. This study was aimed to investigate the mechanism underlying the involvement of NPY gene in the anorectic action of PPA. Results revealed that PPA treatment in rats could decrease both NPY content and mRNA level in the hypothalamus. In addition, the expression of NPY immunoreactivity following PPA treatment was decreased in areas of hypothalamic arcuate nucleus, paraventricular nucleus and periventricular area using immunohistochemical staining, suggesting an involvement of NPYergic pathway in the action of PPA anorexia. Our results provided immunohistochemical and genomic evidence to suggest that PPA might reduce feeding by altering NPY gene expression.

Effects of phenylpropanolamine infusion and withdrawal on body weight and dietary composition in male and female rats

Male and female rats with ad lib access to separate sources of carbohydrate, fat, and protein were implanted with minipumps providing one of three dosages (0.0, 40.0, or 80.0 mg/kg/day) of phenylpropanolamine (PPA) for 2 weeks. Body weight, macronutrient intake, and water consumption were measured daily before, during, and after PPA treatment. Phenylpropanolamine lowered body weight and caloric intake in males and females, and water consumption in females, but did not alter dietary composition in either sex. After PPA termination, caloric intake returned to control levels in both males and females. However, body weight returned to control levels in males only, while PPA-treated females continued to weigh less than controls. Phenylpropanolamine termination was associated with significant increases in water consumption and the percentage of total calories consumed from protein and reductions in the percentage of calories from carbohydrate in males. In contrast, water and macronutrient consumption was similar comparing PPA-treated females to controls after drug termination. These results suggest there are sex differences in the effects of PPA termination on water and macronutrient consumption that result in differential weight gain in males and females.

Inhibition of feeding and hoarding behaviors by phenylpropanolamine in the adult rat

The mechanism by which phenylpropanolamine (PPA) reduces feeding and body lipid is unknown. To determine if malaise associated with PPA treatment mediates its anorexic action, the present study compared the actions of PPA on feeding and hoarding behavior with that of lithium chloride at dose levels that induce comparable conditioned taste aversions. Adult male rats were injected (IP) 30 minutes prior to a test of feeding and hoarding behavior with either 0.9% saline, 32 mg/kg lithium chloride or with 10 mg/kg, 20 mg/kg or 40 mg/kg PPA. Although 32 mg/kg lithium chloride was without effect on either feeding or hoarding behaviors, PPA significantly suppressed both behaviors. These results do not support the notion that malaise is a critical aspect of the anorexic property of PPA and that hoarding behavior may represent a sensitive index of anorexic drug potency.