Involvement of protein kinase C and tyrosine kinase in lipopolysaccharide-induced anorexia

Piperlongumine, a piper alkaloid, enhances the efficacy of doxorubicin in breast cancer: involvement of glucose import, ROS, NF-κB and lncRNAs

Piperlongumine (PL, piplartine) is an alkaloid derived from the Piper longum L. (long pepper) roots. Originally discovered in 1961, the biological activities of this molecule against some cancer types was reported during the last decade. Whether PL can synergize with doxorubicin and the underlying mechanism in breast cancer remains elusive. Herein, we report the activities of PL in numerous breast cancer cell lines. PL reduced the migration and colony formation by cancer cells. An enhancement in the sub-G1 population, reduction in the mitochondrial membrane potential, chromatin condensation, DNA laddering and suppression in the cell survival proteins was observed by the alkaloid. Further, PL induced ROS generation in breast cancer cells. While TNF-α induced p65 nuclear translocation, PL suppressed the translocation in cancer cells. The expression of lncRNAs such as MEG3, GAS5 and H19 were also modulated by the alkaloid. The molecular docking studies revealed that PL can interact with both p65 and p50 subunits. PL reduced the glucose import and altered the pH of the medium towards the alkaline side. PL also suppressed the expression of glucose and lactate transporter in breast cancer cells. In tumor bearing mouse model, PL was found to synergize with doxorubicin and reduced the size, volume and weight of the tumor. Overall, the effects of doxorubicin in cancer cells are enhanced by PL. The modulation of glucose import, NF-κB activation and lncRNAs expression may have contributory role for the activities of PL in breast cancer.

Clinical importance of nonsteroidal anti-inflammatory drug enteropathy: the relevance of tumor necrosis factor as a promising target

The pathogenesis of nonsteroidal anti-inflammatory drug (NSAID) enteropathy is still unclear, and consequently, there is no approved therapeutic strategy for ameliorating such damage. On the other hand, molecular treatment strategies targeting tumor necrosis factor (TNF) exerts beneficial effects on NSAID-induced intestinal lesions in rodents and rheumatoid arthritis patients. Thus, TNF appears to be a potential therapeutic target for both the prevention and treatment of NSAID enteropathy. However, the causative relationship between TNF and NSAID enteropathy is largely unknown. Currently approved anti-TNF agents are highly expensive and exhibit numerous side effects. Hence, in this review, the pivotal role of TNF in NSAID enteropathy has been summarized and plant-derived polyphenols have been suggested as useful alternative anti-TNF agents because of their ability to suppress TNF activated inflammatory pathways both in vitro and in vivo.

Role of nuclear factor κB-mediated inflammatory pathways in cancer-related symptoms and their regulation by nutritional agents

Cancer is a disease characterized by dysregulation of multiple genes and is associated with symptoms such as cachexia, anorexia, fatigue, depression, neuropathic pain, anxiety, cognitive impairment, sleep disorders and delirium (acute confusion state) in medically ill patients. These symptoms are caused by either the cancer itself or the cancer treatment. During the past decade, increasing evidence has shown that the dysregulation of inflammatory pathways contributes to the expression of these symptoms. Cancer patients have been found to have higher levels of proinflammatory cytokines such as interleukin-6. The nuclear factor (NF)-κB is a major mediator of inflammatory pathways. Therefore, anti-inflammatory agents that can modulate the NF-κB activation and inflammatory pathways may have potential in improving cancer-related symptoms in patients. Because of their multitargeting properties, low cost, low toxicity and immediate availability, natural agents have gained considerable attention for prevention and treatment of cancer-related symptoms. How NF-κB and inflammatory pathways contribute to cancer-related symptoms is the focus of this review. We will also discuss how nutritional agents such as curcumin, genistein, resveratrol, epigallocatechin gallate and lycopene can modulate inflammatory pathways and thereby reduce cancer-related symptoms in patients.

Lipopolysaccharide differentially decreases plasma acyl and desacyl ghrelin levels in rats: potential role of the circulating ghrelin-acylating enzyme GOAT

Bacterial lipopolysaccharide (LPS) in rodents is an established model for studying innate immune responses to gram-negative bacteria and mimicking symptoms of infections including reduced food intake associated with decreased circulating total ghrelin levels. The ghrelin-acylating enzyme, ghrelin-O-acyltransferase (GOAT) involved in the formation of acyl ghrelin (AG) was recently identified. We investigated changes in circulating AG, desacyl ghrelin (DG) and GOAT induced by intraperitoneal LPS (100 microg/kg) and associated changes in food intake. Plasma AG and total ghrelin were assessed by radioimmunoassay, GOAT protein by Western blot and mRNA by RT-qPCR. DG was derived from total minus AG. Plasma AG and DG were decreased at 2, 5 and 7 h (p<0.01) post-injection compared to vehicle and recovered at 24 h. At 2 h there was a significantly greater decrease of AG (-53%) than DG (-28%) resulting in a decreased AG/DG ratio (1:5, p<0.01), which thereafter returned to pre-injection values (1:3). This altered ratio was associated with a 38% decrease in plasma GOAT protein compared to vehicle (p<0.001), whereas gastric GOAT protein was slightly increased by 10% (p<0.05). GOAT mRNA expression was unchanged. Food intake was reduced by 58% measured during the 1.5-2 h period post-LPS injection. Decreased plasma AG and DG preceded the rise in rectal temperature and blood glucose that peaked at 7 h. These data indicate that LPS induces a long-lasting reduction of AG and DG levels that may have a bearing with the decrease in food intake. The faster drop in AG than DG within 2 h is associated with reduced circulating GOAT.

Antidipsogenic effects of a TRPV4 agonist, 4α-phorbol 12,13-didecanoate, injected into the cerebroventricle

Transient receptor potential vanilloid 4 (TRPV4) is one member of the TRP superfamily of nonselective cation channels. Recently, the possibility has been raised that TRPV4 is an osmoreceptor, because it is found in the circumventricular organs where osmoreceptors are supposed to be distributed and because it is sensitive to osmotic pressure in in vitro experiments. In addition, TRPV4 knockout mice have abnormal osmosensitivity. In this study, effects of 4α-phorbol 12,13-didecanoate (4α-PDD), a TRPV4 agonist, on drinking behavior were examined to investigate roles for TRPV4 as an osmoreceptor in vivo in wild-type animals. Intracerebroventricular injections of 4α-PDD inhibited water intake under normal conditions in both light and dark periods of the day, after food deprivation, and after administration of angiotensin II. However, this drug did not influence increased water intake after administration of a hypertonic solution or after water deprivation that significantly increased plasma osmolality. Locomotor activity of the 4α-PDD-injected group decreased slightly compared with that of the vehicle-injected group; however, sweet taste, food intake, and body temperature were not different between the two groups. The antidipsogenic effects of 4α-PDD were blocked by preinjection into the ventricle of TRPV4 antagonists such as ruthenium red or gadolinium. These findings suggest that TRPV4 regulates drinking behavior under certain conditions, and the regulation interacts with the angiotensin II pathway.

Mechanisms underlying anorexia after microinjection of bombesin into the lateral cerebroventricle

Intracerebroventricular (i.c.v.) injections of bombesin (BN) and gastrin-releasing peptide (GRP) dose-dependently decreased food intake in male Wistar rats fasted for 17 h. Neuromedin B (NMB) did not show any effect on food intake. After BN administration, locomotor activity did not significantly change, compared with a vehicle-injected group. The anorexia induced by BN (0.3 microg) was perfectly inhibited by pretreatment with a GRP-receptor antagonist, [D-Tyr(6)]BN(6-13) methyl ester (10 microg), an NO synthase inhibitor, L-nitro-arginine (30 microg), and a PKG inhibitor, H-9 (2 microg). The cGMP concentration in the hypothalamus increased 1 h after administration when compared with the vehicle-injected group. On the other hand, an NMB-receptor antagonist, BIM23127 (10 microg), and the protein kinase (PK) C inhibitors, chelerythrine (2 microg) and Go6983 (2 microg), inhibited only the late phase of the anorexia. A PKC activator, phorbol 12, 13-dibutyrate (3 microg), injected into the ventricle decreased food intake. These findings suggest that BN suppresses food intake mainly mediated through the GRP receptor and NO-cGMP-PKG pathway, and NMB receptor and PKC is partly involved in the late phase of the anorexia.

Tyrosine kinase is involved in hemin-induced pyresis

To investigate the mechanisms involved in hemin-induced febrile response, the rectal temperature of rats were measured after intracerebroventricular (i.c.v.) injections of hemin, with or without antagonists. Hemin (10 microg) elicited a significant febrile response, which lasted from 30 min, to more than 6 h, after its administration, but this was not the case with biliverdin (i.c.v.) and bilirubin (i.c.v.). The hemin-induced febrile response was significantly inhibited by pretreatment with an inhibitor of tyrosine kinase (genistein), but not by pretreatment with an inhibitor of protein kinase C (chelerythrine) and a scavenger of iron (deferoxamine). These results suggest that tyrosine kinase is involved in the hemin-induced febrile response.

Pharmacological characteristics of bombesin receptor mediating hypothermia in the central nervous system of rats

Bombesin (BN) and structurally related peptides, gastrin-releasing peptide (GRP) and neuromedin B (NMB), injected into the lateral ventricle produce multiple effects such as hypothermia, anorexia and hormone release. In this study, the pharmacological characteristics of BN receptors mediating hypothermia in the central nervous system (CNS) were investigated using free-moving male Wistar rats. Intracerebroventricular injections of BN, GRP and NMB produced hypothermia in a dose-dependent manner. The BN (0.3 microg)-induced effect showed a short latency and a 4-h duration with a potency increased by more than 100 times compared to the NMB-induced effect. Pretreatment with [D-Tyr(6)]BN(6-13)methylester, a GRP receptor antagonist, inhibited the BN (0.3 microg)- and NMB (7 microg)-induced hypothermia. On the other hand, BIM23127, an NMB receptor antagonist, did not influence the hypothermia. Of the protein kinase C (PKC) inhibitors, chelerythrine, Go6983, staurosporine and GF109203X, the first two partially blocked the BN-induced hypothermia. A PKC activator, phorbol-12,13-dibutyrate, decreased the rectal temperature. Genistein (a tyrosine kinase inhibitor), Y-27632 (a Rho kinase inhibitor) and PD98059 (a MAPK inhibitor) tended to suppress the BN-induced hypothermia, however, these were not significant. The inhibitory effect of a mixture of the three inhibitors, chelerythrine, genistein and Y-27632, on the BN-induced hypothermia was of a similar degree to that of chelerythrine alone. The BN receptor mediating the hypothermia seem to be the GRP subtype, and the effect involves activation of PKC.