Interleukin 1-like factors can accumulate 5-hydroxytryptamine in the liver of mice and can induce hypoglycaemia

Dynamics of Platelet Behaviors as Defenders and Guardians: Accumulations in Liver, Lung, and Spleen in Mice

Systemic platelet behaviors in experimental animals are often assessed by infusion of isotope-labeled platelets and measuring them under anesthesia. However, such procedures alter, therefore may not reveal, real-life platelet behaviors. 5-Hydroxytryptamine (5HT or serotonin) is present within limited cell-types, including platelets. In our studies, by measuring 5HT as a platelet-marker in non-anesthetized mice, we identified stimulation- and time-dependent accumulations in liver, lung, and/or spleen as important systemic platelet behaviors. For example, intravenous, intraperitoneal, or intragingival injection of lipopolysaccharide (LPS, a cell-wall component of Gram-negative bacteria), interleukin (IL)-1, or tumor necrosis factor (TNF)-α induced hepatic platelet accumulation (HPA) and platelet translocation into the sinusoidal and perisinusoidal spaces or hepatocytes themselves. These events occurred "within a few hours" of the injection, caused hypoglycemia, and exhibited protective or causal effects on hepatitis. Intravenous injection of larger doses of LPS into normal mice, or intravenous antigen-challenge to sensitized mice, induced pulmonary platelet accumulation (PPA), as well as HPA. These reactions occurred "within a few min" of the LPS injection or antigen challenge and resulted in shock. Intravenous injection of 5HT or a catecholamine induced a rapid PPA "within 6 s." Intravenous LPS injection, within a minute, increased the pulmonary catecholamines that mediate the LPS-induced PPA. Macrophage-depletion from liver and spleen induced "day-scale" splenic platelet accumulation, suggesting the spleen is involved in clearing senescent platelets. These findings indicate the usefulness of 5HT as a marker of platelet behaviors, and provide a basis for a discussion of the roles of platelets as both "defenders" and "guardians."

Involvement of IL-1 in the Maintenance of Masseter Muscle Activity and Glucose Homeostasis

Physical exercise reportedly stimulates IL-1 production within working skeletal muscles, but its physiological significance remains unknown due to the existence of two distinct IL-1 isoforms, IL-1α and IL-1β. The regulatory complexities of these two isoforms, in terms of which cells in muscles produce them and their distinct/redundant biological actions, have yet to be elucidated. Taking advantage of our masticatory behavior (Restrained/Gnawing) model, we herein show that IL-1α/1β-double-knockout (IL-1-KO) mice exhibit compromised masseter muscle (MM) activity which is at least partially attributable to abnormalities of glucose handling (rapid glycogen depletion along with impaired glucose uptake) and dysfunction of IL-6 upregulation in working MMs. In wild-type mice, masticatory behavior clearly increased IL-1β mRNA expression but no incremental protein abundance was detectable in whole MM homogenates, whereas immunohistochemical staining analysis revealed that both IL-1α- and IL-1β-immunopositive cells were recruited around blood vessels in the perimysium of MMs after masticatory behavior. In addition to the aforementioned phenotype of IL-1-KO mice, we found the IL-6 mRNA and protein levels in MMs after masticatory behavior to be significantly lower in IL-1-KO than in WT. Thus, our findings confirm that the locally-increased IL-1 elicited by masticatory behavior, although present small in amounts, contributes to supporting MM activity by maintaining normal glucose homeostasis in these muscles. Our data also underscore the importance of IL-1-mediated local interplay between autocrine myokines including IL-6 and paracrine cytokines in active skeletal muscles. This interplay is directly involved in MM performance and fatigability, perhaps mediated through maintaining muscular glucose homeostasis.

Modification of energy balance induced by the food contaminant T-2 toxin: a multimodal gut-to-brain connection

T-2 toxin is one of the most toxic Fusarium-derived trichothecenes found on cereals and constitutes a widespread contaminant of agricultural commodities as well as commercial foods. Low doses toxicity is characterized by reduced weight gain. To date, the mechanisms by which this mycotoxin profoundly modifies feeding behavior remain poorly understood and more broadly the effects of T-2 toxin on the central nervous system (CNS) have received limited attention. Through an extensive characterization of sickness-like behavior induced by T-2 toxin, we showed that its per os (p.o.) administration affects not only feeding behavior but also energy expenditure, glycaemia, body temperature and locomotor activity. Using c-Fos expression mapping, we identified the neuronal structures activated in response to T-2 toxin and observed that the pattern of neuronal populations activated by this toxin resembled that induced by inflammatory signals. Interestingly, part of neuronal pathways activated by the toxin were NUCB-2/nesfatin-1 expressing neurons. Unexpectedly, while T-2 toxin induced a strong peripheral inflammation, the brain exhibited limited inflammatory response at a time point when anorexia was ongoing. Unilateral vagotomy partly reduced T-2 toxin-induced brainstem neuronal activation. On the other hand, intracerebroventricular (icv) T-2 toxin injection resulted in a rapid (<1h) reduction in food intake. Thus, we hypothesized that T-2 toxin could signal to the brain through neuronal and/or humoral pathways. The present work provides the first demonstration that T-2 toxin modifies feeding behavior by interfering with central neuronal networks devoted to central energy balance. Our results, with a particular attention to peripheral inflammation, strongly suggest that inflammatory mediators partake in the T-2 toxin-induced anorexia and other symptoms. In view of the broad human and breeding animal exposure to T-2 toxin, this new mechanism may lead to reconsider the impact of the consumption of this toxin on human health.

Primary role of interleukin-1 alpha and interleukin-1 beta in lipopolysaccharide-induced hypoglycemia in mice

Within a few hours of its injection into mice, lipopolysaccharide (LPS) induces hypoglycemia and the production of various cytokines. We previously found that interleukin-1 alpha (IL-1 alpha), IL-1 beta, and tumor necrosis factor alpha (TNF-alpha) induce hypoglycemia and that the minimum effective dose of IL-1 alpha or IL-1 beta is about 1/1000 that of TNF-alpha. In the present study, we examined the contribution made by IL-1 to the hypoglycemic action of LPS. Nine other cytokines tested were all inactive at inducing hypoglycemia. LPS produced hypoglycemia in mice deficient in either IL-1 alpha or IL-1 beta but not in mice deficient in both cytokines (IL-1 alpha and -1 beta knockout [IL-1 alpha/beta KO] mice). IL-1 alpha, IL-1 beta, and TNF-alpha induced hypoglycemia in IL-1 alpha/beta KO mice, as they did in normal control mice. The LPS-induced elevation of serum cortisol was weaker in IL-1 alpha/beta KO mice than in control mice, and, in the latter, serum cortisol was markedly raised while blood glucose was declining. IL-1 alpha decreased blood glucose both in NOD mice (which have impaired insulin production) and in KK-Ay mice (insulin resistant). These results suggest that (i). cortisol may not be involved in mediating the resistance of IL-1 alpha/beta KO mice to the hypoglycemic action of LPS, (ii). as a mediator, IL-1 is a prerequisite for the hypoglycemic action of LPS, (iii). IL-1 alpha and IL-1 beta perform mutual compensation, and (iv). IL-1 plays a role as the primary stimulator of the many anabolic reactions required for the elaboration of immune responses against infection.

Inhibition of inflammatory actions of aminobisphosphonates by dichloromethylene bisphosphonate, a non-aminobisphosphonate

1. When injected intraperitoneally into mice in doses larger than those used clinically, all the amino derivatives of bisphosphonates (aminoBPs) tested induce a variety of inflammatory reactions such as induction of histidine decarboxylase (HDC, the histamine-forming enzyme), hypertrophy of the spleen, atrophy of the thymus, hypoglycaemia, ascites and accumulation of exudate in the thorax, and an increase in the number of macrophages and/or granulocytes in the peritoneal cavity of blood. On the other hand, dichloromethylene bisphosphonate (Cl2MBP) a typical non-aminoBP, has no such inflammatory actions. In the present study, we found that this agent can suppress the inflammatory actions of aminoBPs. 2. Cl2MBP, when injected into mice before or after injection of 4-amino-1-hydroxybutylidene-1,1-bisphosphonic acid (AHBuBP; a typical aminoBP), inhibited the induction of HDC activity by AHBuBP in a dose- and time-dependent manner. The increase in HDC activity induced by AHBuBP was largely suppressed by the injection of an equimolar dose of Cl2MBP. Cl2MBP also inhibited other AHBuBP-induced inflammatory reactions, as well as the inflammatory actions of two other aminoBPs. However, Cl2MBP did not inhibit the increase in HDC activity induced by lipopolysaccharide (LPS). 3. We have previously reported that AHBuBP augments the elevation of HDC activity and the production of interleukin-1beta (IL-1beta) that are induced by LPS. These actions of AHBuBP were also inhibited by Cl2MBP. 4. Based on these results and reported actions of bisphosphonates, the mechanisms underlying the contrasting effects of aminoBPs and Cl2MBP, a non-aminoBP are discussed. The results suggest that combined administration of Cl2MBP and an aminoBP in patients might be a useful way of suppressing the inflammatory side effects of aminoBPs.

Translocation of platelets into Disse spaces and their entry into hepatocytes in response to lipopolysaccharides, interleukin-1 and tumour necrosis factor: the role of Kupffer cells

BACKGROUND/AIMS

Injection into mice of a small dose of either a lipopolysaccharide or interleukin-1 induces a slowly developing accumulation of 5-hydroxytryptamine, predominantly in the liver. We have established that this 5-hydroxytryptamine accumulation is the result of the translocation of platelets to hepatic sinusoidal spaces and, further, into Disse spaces, and that the platelets make direct contact with hepatocytes. In the present study, we report our recent findings on this phenomenon.

METHODS

Platelets contain a large amount of 5-hydroxytryptamine, but the 5-hydroxytryptamine content of the liver is normally very small. Therefore, the translocation of platelets to the liver was assessed by measuring 5-hydroxytryptamine as in previous studies, and it was also analysed by electron microscopy.

RESULTS

Anti-platelet agents, such as heparin and inhibitors of prostaglandin synthesis, were ineffective in preventing the lipopolysaccharide-induced accumulation of 5-hydroxytryptamine in the liver. Of the various cytokines tested, only interleukin-1 and tumour necrosis factor induced such an accumulation of 5-hydroxytryptamine. Intravenous injection of liposomes encapsulating dichloromethylene bisphosphonate resulted in an almost complete depletion of macrophages from the liver. The lipopolysaccharide- and cytokine-induced hepatic accumulations of 5-hydroxytryptamine were abolished almost completely in such macrophage-depleted mice. Electron microscopy revealed no accumulation of platelets in the liver after injection of lipopolysaccharide into the macrophage-depleted mice. Surprisingly, in normal mice injected with lipopolysaccharide, several platelets were found inside some hepatocytes, even though there was no visible damage to these hepatocytes. In fact, there were many polysomes around the degranulated platelets within the hepatocytes, suggesting an enhanced protein synthesis.

CONCLUSION

These results suggest that, in response to lipopolysaccharide, interleukin-1 or tumour necrosis factor, platelets translocate into the liver in a way that is different from aggregation, and that some, at least, enter hepatocytes. During these processes, hepatic macrophages play an essential role.

Biphasic, organ-specific, and strain-specific accumulation of platelets induced in mice by a lipopolysaccharide from Escherichia coli and its possible involvement in shock

Platelets contain a large amount of 5-hydroxytryptamine (5HT, serotonin). Intravenous injection into BALB/c mice of a Boivin's preparation of lipopolysaccharide (LPS) from Escherichia coli induced rapid 5HT accumulation in the lung (within 5 min) and slow 5HT accumulation in the liver (2 to 5 h later). The rapid response required high doses of LPS (more than 0.1 mg/kg). On the basis of 5HT measurements, 70% or more of the platelets which disappeared from the blood appeared to have accumulated rapidly in the lung, and a large number of platelets were found there by electron microscopy. A shock, which was manifested by crawling, convulsion, or prostration, followed shortly after the rapid accumulation of 5HT in the lung. On the other hand, the slow accumulation of 5HT in the liver could be induced by much lower doses of LPS (1 microg/kg or less), even when given by intraperitoneal injection. This 5HT accumulation appears to be a reflection of platelet accumulation in the liver (Y. Endo and M. Nakamura, Br. J. Pharmacol. 105:613-619, 1992). The combination of a low dose of LPS with D-galactosamine amplified the hepatic accumulation of 5HT, and the mice developed a severe hepatic congestion resulting in death. The rapid response was not induced at all in C3H/HeN mice. These results and comparison with other LPS preparations indicate that some component(s) of LPS from E. coli induces a biphasic, organ-specific and strain-specific accumulation of platelets, and it is proposed that this effect is involved in the development of shock.

Active translocation of platelets into sinusoidal and Disse spaces in the liver in response to lipopolysaccharides, interleukin-1 and tumor necrosis factor

1. Injection of lipopolysaccharides (LPS) or endotoxin into mice and rats induces a prolonged increase in serotonin (5-hydroxytryptamine: 5HT), predominantly in the liver. 2. The 5HT increase reflects the accumulation of platelets in the sinusoidal and perisinusoidal Disse spaces (spaces between endothelial cells and hepatocytes) in the liver. 3. Most of the platelets which accumulated in these spaces still retained their intact structure and a large amount of 5HT. 4. Interleukin-1 and/or tumor necrosis factor also induce the platelet response. 5. Kupffer's cells play a key role in this platelet response. 6. Anti-platelet drugs currently used, except for anti-inflammatory steroids, were ineffective in preventing the platelet response. 7. This platelet response is different from the well known platelet aggregation. 8. The possible involvement of this platelet response in insulin-independent hypoglycaemia, disseminated intravascular coagulation, septic shock, hepatitis, Shwartzman type reactions or self-defense mechanisms is discussed.

The effect of lipopolysaccharide, interleukin-1 and tumour necrosis factor on the hepatic accumulation of 5-hydroxytryptamine and platelets in the mouse

1. Injection of lipopolysaccharide (LPS; 0.5-500 microgram kg-1) into mice induced a dose-dependent, slowly developing increase in hepatic content of 5-hydroxytryptamine (5-HT). This sustained increase could not be attributed to an LPS-induced alteration of the pharmacokinetic handling of 5-HT by stimulation of its uptake or inhibition of its degradation. 2. Regional differences were apparent in the tissue content of histamine and 5-HT between mast cell-deficient (W/Wv) and normal (+/+) mice. LPS administration (0.5 mg kg-1) gave comparable increases in the hepatic level of 5-HT in mast cell-deficient and normal mice. 3. Reserpine pretreatment (1 mg kg-1) selectively reduced 5-HT levels in the blood, spleen, liver, brain and lung of normal mice. Prior treatment with this agent also abolished the LPS (0.5 mg kg-1)-induced hepatic accumulation of 5-HT. 4. Accumulation of 5-HT in the liver by LPS (0.1 mg kg-1) was temporally associated with both a fall in the levels of circulating platelets, and a reduction in the concentration of 5-HT in the blood. The LPS dose-dependent (0.5-500 micrograms kg-1) increase in hepatic 5-HT content was associated with a similar dose-dependent reduction in the circulating levels of 5-HT. 5. Interleukin-1, alpha and beta (10 micrograms kg-1) and tumour necrosis factor alpha (TNF alpha) (1 mg kg-1) significantly enhanced the accumulation of 5-HT within the liver. Administration of TNF alpha (10 micrograms kg-1) potentiated the increase in hepatic 5-HT content seen with IL-1 beta (10 micrograms kg-1). 6. Electron microscopy revealed numerous platelets in the sinusoidal and perisinusoidal Disse spaces within the liver, in animals pretreated with LPS (0.1 mg kg '). The platelets retained their intact structure and showed no evidence of degranulation. 7. These data suggest that the LPS and cytokine-induced mobilization of 5-HT in the liver is associated with the hepatic translocation of platelets. This migration appears to be independent of platelet aggregation.

Parallel relationship between the increase in serotonin in the liver and the hypoglycaemia induced in mice by interleukin-1 and tumour necrosis factor

Endotoxins or lipopolysaccharides (LPS), when injected into mice, increase serotonin (5-hydroxytryptamine; 5HT) in the liver and produce hypoglycaemia. In the present study, it was found that the cytokines produced by macrophages in response to LPS, interleukin-1 (IL-1, 0.1 microgram/kg or more) and tumour necrosis factor (TNF alpha, 100 micrograms/kg or more), can also induce an increase in liver serotonin and produce hypoglycaemia. The two responses correspond well with each other in terms of time course and dose dependency. These results suggest that the two responses induced by LPS may be mediated by IL-1 and/or TNF alpha and that the phenomenon of accumulation of 5HT in the liver may be relevant to hypoglycaemia. The hypoglycaemic response to IL-1 was moderate at a wide dose range but was induced by smaller amounts than with insulin.

Interleukin 6 stimulates hepatic glucose release from prelabeled glycogen pools

Cytokines, derived from a wide variety of cell types, are now believed to initiate many of the physiological responses accompanying the inflammatory phase that follows either Gram-negative septicemia or thermal injury. Because hypoglycemia (after endotoxic challenge) and hyperglycemia (after thermal injury) represent well-characterized responses to these injuries, we sought to determine whether hepatic glycogen metabolism could be altered by specific cytokines. Cultured adult rat hepatocytes were prelabeled with [14C]glucose for 24 h, a procedure that resulted in the labeling of hepatic glycogen pools that subsequently could be depleted (with concomitant [14C]glucose release) by either glucagon or norepinephrine. After the addition of a highly concentrated human monocyte-conditioned medium (MCM) or various cytokines to these prelabeled cells, [14C]glucose release was stimulated by MCM and recombinant human interleukin 6 (IL-6) but was not stimulated by other cytokines tested. Furthermore, only antisera to IL-6 were capable of reducing the glucose-releasing factor activity found in MCM. These data therefore suggest a novel glucoregulatory role for IL-6.

A sensitive IL-1 thymocyte co-stimulator assay using a novel beta-D-galactoside specific lectin from the beetle, Allomyrina dichotoma

A sensitive thymocyte co-stimulator assay of IL-1 using a beta-D-galactoside specific lectin (allo A) obtained from the beetle (Allomyrina dichotoma) is reported here. Allo A stimulated [3H]thymidine uptake of mouse thymocytes in the presence of IL-1. The allo A assay was more sensitive than the PHA or PNA- thymocyte assay, especially at low doses of IL-1. Optimal conditions for the allo A assay were as follows: allo A, 2.5-5.0 micrograms/ml; whole thymocytes, 0.5-1.0 x 10(6) cells/well; incubation time, 72-96 hr. The assay is sensitive and convenient and can easily be performed in any laboratory.

Suppression and potentiation of 5-hydroxytryptophan-induced hypoglycaemia by alpha-monofluoromethyldopa: correlation with the accumulation of 5-hydroxytryptamine in the liver

Experiments were done to examine whether the accumulation of 5-hydroxytryptamine (5-HT) in the liver is responsible for the hypoglycaemia induced in mice by 5-hydroxytryptophan (5-HTP) and lipopolysaccharides (LPS). (+/-)-alpha-Monofluoromethyldopa (FMD), a potent irreversible inhibitor of aromatic amino acid decarboxylase, suppressed the 5-HTP-induced accumulation of 5-HT in the liver at a dose of 2 mg kg-1 or more, but potentiated the accumulation at lower dose of 0.4 mg kg-1. Corresponding to these effects, the hypoglycaemic response was prevented by the higher doses of FMD and potentiated by the lower dose. These contrasting effects of FMD were explicable by the amounts of 5-HTP entering the liver. In contrast, FMD did not prevent either the hypoglycaemia or the accumulation of 5-HT in the liver induced by LPS. These results further support the hypothesis that the accumulation of 5-HT in the liver is causally related to the hypoglycaemia induced by 5-HTP and indicate that the LPS-induced 5-HT accumulation in the liver is not derived from stimulation of 5-HT synthesis. It is still not clear whether the accumulation of 5-HT in the liver is involved in the hypoglycaemic response to LPS.

Macrophages can produce factors capable of inducing histidine decarboxylase, a histamine-forming enzyme, in vivo in the liver, spleen, and lung of mice

Injection into mice of culture supernatant of P388D1 cells, a murine macrophage cell line, produced a rapid increase in histidine decarboxylase (HDC) activities in the liver, spleen, and lung. Factors in the culture supernatant capable of inducing the HDC elevation were purified by gel filtration and chromatofocusing. Throughout these procedures, the HDC-inducing activity accompanied the mitogenic activity for thymocytes or interleukin 1 (IL-1) activity. Although, because of low purity of the preparations, it is not confirmed whether the HDC inducer is IL-1 itself or not, the present results indicate that P388D1 cells can produce a factor(s) capable of inducing HDC in mouse tissues in vivo. After the injection of the HDC-inducing factor into mice, HDC induction in the tissues occurred within 2 hr and peaked at 2 to 4 hr, resulting in the increase in histamine levels 1 to 10 nmol/g tissue. These results provide important information concerning the source of endogenous histamine that might be involved in inflammatory reactions in delayed-hypersensitivity reactions or in the immune regulation observed in many in vitro systems.