Anti-Tumor Activity of Hypericum perforatum L. and Hyperforin through Modulation of Inflammatory Signaling, ROS Generation and Proton Dynamics

In this paper we review the mechanisms of the antitumor effects of Hypericum perforatum L. (St. John's wort, SJW) and its main active component hyperforin (HPF). SJW extract is commonly employed as antidepressant due to its ability to inhibit monoamine neurotransmitters re-uptake. Moreover, further biological properties make this vegetal extract very suitable for both prevention and treatment of several diseases, including cancer. Regular use of SJW reduces colorectal cancer risk in humans and prevents genotoxic effects of carcinogens in animal models. In established cancer, SJW and HPF can still exert therapeutic effects by their ability to downregulate inflammatory mediators and inhibit pro-survival kinases, angiogenic factors and extracellular matrix proteases, thereby counteracting tumor growth and spread. Remarkably, the mechanisms of action of SJW and HPF include their ability to decrease ROS production and restore pH imbalance in tumor cells. The SJW component HPF, due to its high lipophilicity and mild acidity, accumulates in membranes and acts as a protonophore that hinders inner mitochondrial membrane hyperpolarization, inhibiting mitochondrial ROS generation and consequently tumor cell proliferation. At the plasma membrane level, HPF prevents cytosol alkalization and extracellular acidification by allowing protons to re-enter the cells. These effects can revert or at least attenuate cancer cell phenotype, contributing to hamper proliferation, neo-angiogenesis and metastatic dissemination. Furthermore, several studies report that in tumor cells SJW and HPF, mainly at high concentrations, induce the mitochondrial apoptosis pathway, likely by collapsing the mitochondrial membrane potential. Based on these mechanisms, we highlight the SJW/HPF remarkable potentiality in cancer prevention and treatment

Protective role of St. John's Wort and its components hyperforin and hypericin against diabetes through Inhibition of inflammatory signaling: evidence from in vitro and in vivo studies

Diabetes mellitus is a very common chronic disease with progressively increasing prevalence. Besides the well-known autoimmune and inflammatory pathogenesis of type 1 diabetes, in many people, metabolic changes and inappropriate lifestyle favor a subtle chronic inflammatory state that contributes to development of insulin resistance and progressive loss of β-cell function and mass, eventually resulting in metabolic syndrome or overt type 2 diabetes. In this paper, we review the anti-inflammatory effects of the extract of Hypericum perforatum L. (St. John's wort, SJW) and its main active ingredients firstly in representative pathological situations on inflammatory basis and then in pancreatic β cells and in obese or diabetic animal models. The simultaneous and long-lasting inhibition of signal transducer and activator of transcription (STAT)-1, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinases (MAPKs)/c-jun N-terminal kinase (JNK) signaling pathways involved in pro-inflammatory cytokine-induced β-cell dysfunction/death and insulin resistance make SJW particularly suitable for both preventive and therapeutic use in metabolic diseases. Hindrance of inflammatory cytokine signaling is likely dependent on the hyperforin content of SJW extract, but recent data reveal that hypericin can also exert relevant protective effects, mediated by activation of the cyclic adenosine monophosphate (cAMP)/protein kinase cAMP-dependent (PKA)/adenosine monophosphate activated protein kinase (AMPK) pathway, against high-fat-diet-induced metabolic abnormalities. Actually, the mechanisms of action of the two main components of SJW appear complementary, strengthening the efficacy of the plant extract. Careful quantitative analysis of SJW components and suitable dosage, with monitoring of possible drug-drug interaction in a context of remarkable tolerability, are easily achievable pre-requisites for forthcoming clinical applications

Protein glycation in the aging male Sprague-Dawley rat: effects of antiaging diet restrictions

Protein glycation and accumulation of advanced glycosylated end-products (AGEs) are supposed to play an important role in the process of aging. Dietary restriction increases life span and delays the onset of most age-associated diseases. Age-dependent changes in glucose homeostasis and glycated plasma proteins and hemoglobin were determined, and AGEs formation was measured as fluorescence in skin and aortic collagens in male Sprague-Dawley rats fed ad libitum or subjected to every-other-day feeding or 40% food restriction. In aging control rats, skin and aortic collagen-linked fluorescence increased with a similar exponential curve (aortic value being always higher), whereas glycated plasma protein and hemoglobin decreased slightly. Dietary restrictions decreased glycated plasma proteins and fluorescent products in skin collagen of younger but not older rats, and did not affect glycated hemoglobin or aortic collagen fluorescence. In conclusion, our data indicate that age-related changes in glucose homeostasis do not play a substantial role in aging; and collagen-linked fluorescence increases significantly during aging, but it may not be sensitive to dietary intervention

Impairment of the priming effect of glucose on insulin secretion from isolated islets of aging rats

The time-dependent potentiation (TDP) of insulin release or priming effect exerted by glucose was evaluated in the islets of Langerhans of mature and old rats. Islets isolated from 12- and 26-month-old male Sprague-Dawley rats and incubated for two consecutive 60-min periods in the presence of various stimulating agents were unable to enhance their insulin responsiveness significantly during the second incubation period and showed other abnormalities in their sensitivity to secretagogues compared with islets from 3-month-old animals. The priming action of glucose plus arginine or isobutylmethylxanthine (IBMX) was not observed in islets from 12-month-old rats, but surprisingly, islets from senescent rats showed a restoration of the beta-cell memory in the presence of IBMX. Interestingly, the islets isolated from 2-month-old animals previously exposed to an intravenous glucose load in vivo released approximately twice as much insulin as the islets taken from fed rats not subjected to the load. This potentiation exerted by the intravenous glucose administration was reduced but not abolished in the islets of glucose-intolerant, 12-month-old rats. In conclusion, the glucose TDP of insulin secretion is impaired in islets of mature and old rats, confirming an early loss of sensitivity of beta-cells to secretagogues during agin

Effects of age, diet and obesity on insulin secretion from isolated perfused rat pancreas: Response to glucose, arginine and glucagon-like peptide 1 (7-37)

The insulin secretory responses to glucose, arginine and glucagon-like peptide (GLP)-1-(7- 37 have been evaluated from the isolated perfused pancreas of rats with either acquired or genetic obesity, ie, a) fed ad libitum 14-mo old Sprague-Dawley rats as compared to age-matched animals subjected to two types of dietary restriction (every-other-day feeding, EOD, and 40% restriction? 40% DR), and b) 2.5-mo old genetically obese fa/fa rats as compared to the lean counterpart, In mature fed ad libitum rats, the glucose-stimulated insulin release from the perfused pancreas was increased 5-fold by addition of 0.1 nM GLP-1 (7-37), a subsequent challenge with high glucose resulted in an improvement of the first phase of insulin release, In 40% DR rats, a similar pattern of secretion was observed, with the difference of a lower response to arginine than in fed ad libitum animals, In EOD rats, the overall secretory performance of the perfused pancreas was approximately 50% lower than in the fed ad libitum group but probably adequate to the reduced weight of the animals, In genetically obese young rats, both the response to GLP-1 (7-37) anti the total insulin secretion were higher than in the lean controls. Interestingly, the maximal insulin outputs from the perfused pancreases were observed in both the groups of overweight animals, In conclusion no impairment in the secretory responsiveness of beta-cells occurs in obese animals, Conversely, at least within the age limits of the present study, the endocrine pancreas develops a compensatory ability to match the augmented insulin demand due to the over-weight. In the light of the observed great sensitivity of the isolated perfused pancreas to GLP-1 (7-37), changes in the responsiveness of beta-cells to incretins might be involved in the modulation of the endocrine pancreatic function of obese rats

Age-dependent reduction in GLUT-2 levels is correlated with the impairment of the insulin secretory response in isolated islets of Sprague-Dawley rats.

In this study we have investigated the insulin secretory response to glucose and other secretagogues (2-ketoisocaproate, 3-isobutyl-1-methyl-xanthine and arginine) of pancreatic islets isolated from Sprague-Dawley rats of various ages (from 2 to 28 months). Our results showed a significant decline in the glucose-stimulated insulin secretion, starting at 12 months of age. On the other hand, the response to non-glucose secretagogues (and mainly to 2-ketoisocaproate) was less impaired with advancing age than that to glucose. We also observed a progressive age-related decline of protein levels of the glucose transporter GLUT-2 in pancreatic islets, which was temporally concomitant and quantitatively comparable with the beta-cell alteration in glucose responsiveness (-40/50%). Finally, we observed a significant increase of the islets insulin content in older rats with respect to younger animals. We conclude that in the islet of older rats the impaired capability to respond to glucose could be dependent, at least in part, on the age-dependent reduction in GLUT-2 and could be compensated by mechanisms including a preserved responsiveness to non-glucose secretagogues and/or the development of islet hypertrophy

Effects of life-long exercise on circulating free fatty acids and muscle triglyceride content in ageing rats.

Regular physical exercise has emerged, together with dietary restriction, as an effective intervention in delaying degenerative diseases and augmenting life span in rodents. The mechanisms involved remain largely unknown, although a beneficial influence on the age-related alteration of insulin sensitivity has been hypothesized. As muscle triglyceride (TG) accumulation is considered a reliable index of muscle insulin resistance, in this study we explored muscle TG content in 23-month-old male Sprague-Dawley rats subjected to life-long training. Plasma glucose. insulin. free fatty acid (FFA) and leptin levels were also measured. Both voluntary running in wheels (RW) and forced training in treadmill (TM) were studied. As RW rats weighed less than controls, a cohort of untrained animals, fed to pair weight (PW) with RW, was added to discriminate the effect of exercise from that of food restriction. Sedentary ad libitum fed rats served as controls. In 23-month-old RW rats. muscle TG content was reduced by 50% with respect to age-matched sedentary controls, while in TM group this reduction was smaller but still highly significant, and occurred independently on the changes in body fat mass. In both the trained rat groups, there was a significant decrease in circulating FFA levels and a trend to reduced insulin levels. In PW rats, muscle TG levels decreased similarly to RW rats, while plasma parameters were less modified. In particular, RW training was more effective than PW in preventing the age-related increase in circulating leptin levels. Our results suggest that voluntary exercise effectively counteracts the development of insulin resistance in the muscles of ageing rats as well as other related changes such as hyperlipacidaemia and compensatory hyperleptinaemia. Forced training or moderate food restriction appear slightly less effective than voluntary exercise in preventing age-dependent alterations in nutrient distribution and/or utilization. (C) 2004 Elsevier Inc. All rights reserved

Plasma protein's glycation is decreased in Sprague Dawley rats under caloric restriction.

Different dietary regimens were applied to three cohorts of rats. The first was fed ad libitum every day (AL), the second was fed ad libitum every other day (EOD) and the third was fed a diet equivalent to 60% of the caloric intake (60% CI) of the AL cohort. Levels of stable early glycation products in plasma proteins were then measured according to two different methods, Glycation of plasma proteins progressively increased in AL animals belonging to the 2-12 month age interval, while it showed a less pronounced age-dependent increase in EOD and 60% CI animals. The lowest degree of glycation was detected 2-3 months after the beginning of caloric restriction, After 12 months of age a lower level of glycation was detected in 60% CI rats than in EOD animals, Body weight was lower in restricted animals than in AL animals and was lowest in 60% CI rats. During the life span, glycemia was lower in fasting 60% CI than in EOD or AL rats

ENDOCRINE AND AMINO-ACID REGULATION OF LIVER MACROAUTOPHAGY AND PROTEOLYTIC FUNCTION

Endocrine and amino acid regulation of liver macroautophagy and proteolytic function. Am, J. Physiol. 266 (Gastrointest. Liver Physiol. 29): G118-G122, 1994.-Regulation of liver macroautophagy and protein degradation by hormones and direct regulatory amino acids were studied in male 2-mo-old Sprague-Dawley albino rats with the use of the antilipolytic agent 3,5'-dimethylpyrazole (DMP; 12 mg/kg body wt ip) as a stimulatory agent. Injection of DMP decreased glutamine plasma levels and glutamine release from the perfused liver. Autophagic vacuoles were observed in the pericanalicular area of liver cells after 30 min. Levels and release of other regulatory amino acids did not exhibit any significant decrease but subsequently increased. Intraperitoneal administration of glutamine inhibited the proteolytic response. In conclusion, these studies demonstrate that in vivo induction and control of liver macroautophagy and protein degradation by the physiological mechanism (i.e., by shortage of nutrients) involve unbalanced and asynchronous changes in the levels of selected direct regulatory amino acids (i.e., a decrease in glutamine and a subsequent increase in leucine and tyrosine levels)

Effects of low-dose VOSO4 on age-related changes in glucose homeostasis in rats

The effects of low doses of vanadyl sulfate (0.2 mg/ml in the drinking water) on the age-related impairment of glucose homeostasis in Sprague-Dawley rats were investigated. VOSO(4) administration was initiated in 5-month-old animals and lasted 3 months. Thus, in 8-month-old rats, we investigated glucose metabolism in vivo and insulin secretory function in vitro. Results showed that VOSO(4) allowed the disposal of an oral glucose load at lower insulin levels than in age-matched controls. No significant changes were found in muscle glucose transporter (GLUT-4) levels or in glycogen content upon VOSO(4) treatment. Islets isolated from VOSO(4)-treated rats released less insulin than control islets, but showed a better preserved sensitivity to secretagogues, in terms of incremental release over basal release, secretory efficiency, and maintenance of the priming effect of glucose. In conclusion, chronic low-dose VOSO(4) treatment facilitates insulin action by a mechanism independent of muscle GLUT-4 levels and helps preserve the appropriate sensitivity of beta cells to stimuli, thereby preventing age-dependent functional alterations