Role of pentoxifylline in non-alcoholic fatty liver disease in high-fat diet-induced obesity in mice

AIM: To study pentoxifylline effects in liver and adipose tissue inflammation in obese mice induced by high-fat diet (HFD).

METHODS: Male swiss mice (6-wk old) were fed a high-fat diet (HFD; 60% kcal from fat) or AIN-93 (control diet; 15% kcal from fat) for 12 wk and received pentoxifylline intraperitoneally (100 mg/kg per day) for the last 14 d. Glucose homeostasis was evaluated by measurements of basal glucose blood levels and insulin tolerance test two days before the end of the protocol. Final body weight was assessed. Epididymal adipose tissue was collected and weighted for adiposity evaluation. Liver and adipose tissue biopsies were homogenized in solubilization buffer and cytokines were measured in supernatant by enzyme immunoassay or multiplex kit, respectively. Hepatic histopathologic analyses were performed in sections of paraformaldehyde-fixed, paraffin-embedded liver specimens stained with hematoxylin-eosin by an independent pathologist. Steatosis (macrovesicular and microvesicular), ballooning degeneration and inflammation were histopathologically determined. Triglycerides measurements were performed after lipid extraction in liver tissue.

RESULTS: Pentoxifylline treatment reduced microsteatosis and tumor necrosis factor (TNF)-α in liver (156.3 ± 17.2 and 62.6 ± 7.6 pg/mL of TNF-α for non-treated and treated obese mice, respectively; P < 0.05). Serum aspartate aminotransferase levels were also reduced (23.2 ± 6.9 and 12.1 ± 1.6 U/L for non-treated and treated obese mice, respectively; P < 0.05) but had no effect on glucose homeostasis. In obese adipose tissue, pentoxifylline reduced TNF-α (106.1 ± 17.6 and 51.1 ± 9.6 pg/mL for non-treated and treated obese mice, respectively; P < 0.05) and interleukin-6 (340.8 ± 51.3 and 166.6 ± 22.5 pg/mL for non-treated and treated obese mice, respectively; P < 0.05) levels; however, leptin (8.1 ± 0.7 and 23.1 ± 2.9 ng/mL for non-treated and treated lean mice, respectively; P < 0.05) and plasminogen activator inhibitor-1 (600.2 ± 32.3 and 1508.6 ± 210.4 pg/mL for non-treated and treated lean mice, respectively; P < 0.05) levels increased in lean adipose tissue. TNF-α level in the liver of lean mice also increased (29.6 ± 6.6 and 75.4 ± 12.6 pg/mL for non-treated and treated lean mice, respectively; P < 0.05) while triglycerides presented a tendency to reduction.

CONCLUSION: Pentoxifylline was beneficial in obese mice improving liver and adipose tissue inflammation. Unexpectedly, pentoxifylline increased pro-inflammatory markers in the liver and adipose tissue of lean mice.

Participation of leptin in the determination of the macrophage phenotype: an additional role in adipocyte and macrophage crosstalk

Macrophages develop into specialized cell types with special functional properties, depending on locally produced stimuli. Adipose tissue macrophages present particular characteristics, such as the M2 cell phenotype, and produce cytokines and chemokines usually produced by M1 cells. Our aim was to study the role of leptin, which is an adipokine produced and released by adipocytes, in the induction of these characteristics in macrophages found in the adipose tissue. Human CD14(+) cells were obtained and maintained in culture with IFN-γ (classical M1 phenotype), IL-4 (alternative M2 phenotype) or leptin for 5 d. Surface marker expression was then analyzed by cytometry. In addition, the release of tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, IL-1β, IL-10, IL-1ra, MCP-1, MIP-1α, and RANTES was quantified by ELISA after an LPS stimulus, in the culture supernatant. Macrophages exposed to leptin in culture expressed surface markers that were more similar to the M2 phenotype, but they were able to produce TNF-α, IL-6, IL-1β, IL-1ra, IL-10, MCP-1, and MIP-1α, as observed for M1 cells. Results suggest that leptin strongly contributes to the phenotype observed in macrophages found in adipose tissue.

Effects of methotrexate on inflammatory alterations induced by obesity: an in vivo and in vitro study

Immunosuppressant drugs, such as methotrexate, are able to inhibit cytokine production and leukocyte migration to inflammatory foci; therefore, they could modify the establishment of inflammation in adipose tissue during obesity. Thus, we studied the effects of methotrexate in vivo on high-fat diet induced-obesity in mice and in vitro in isolated and co-cultured adipocytes and macrophages. Obese mice treated with methotrexate presented reduced serum levels of TNF-α, insulin and glucose, and an improvement of insulin sensitivity. Adipose tissue from these mice produced less proinflammatory (TNF-α, IL-6, leptin) and more anti-inflammatory adipokines (adiponectin and IL-10) associated with reduced macrophage infiltration and inflammation. Cytokine inhibition was also confirmed in isolated and co-cultured adipocytes and macrophages. Methotrexate presented anti-lipolytic effect in vivo and, in vitro through adenosine release. Drugs that combine anti-lipolytic effect and the ability to control inflammation in adipose tissue could play a role in the control of insulin resistance and other pathologies associated with obesity.

Infliximab modifies mesenteric adipose tissue alterations and intestinal inflammation in rats with TNBS-induced colitis

OBJECTIVE

Infliximab is a monoclonal anti-TNF-α antibody that is used therapeutically to treat Crohn's disease (CD). High levels of pro-inflammatory cytokines, especially TNF-α, have been observed in the gastrointestinal tract of CD patients and were associated with alterations in the mesenteric adipose tissue, which also contributed to the high levels of adipokine release. The authors used a rat model of colitis that produces mesenteric adipose tissue alterations that are associated with intestinal inflammation to study the effects that infliximab treatment has on adipokine production, morphological alterations in adipose tissue and intestinal inflammation.

MATERIAL AND METHODS

The ability of infliximab to neutralize rat TNF-α was evaluated in vitro using U937 cells. Colitis was induced by repeated intracolonic trinitrobenzene sulfonic acid instillations and was evaluated by macroscopic score, histopathological analysis, myeloperoxidase activity, TNF-α and IL-10 expression as well as iNOS (inducible NO synthase) expression and JNK phosphorylation in colon samples. The alterations in adipose tissue were assessed by TNF-α, IL-10, leptin, adiponectin and resistin levels as well as adipocyte size and peroxisome proliferator-activated receptor (PPAR)-γ expression.

RESULTS

Infliximab treatment controlled intestinal inflammation, which reduced lesions and neutrophil infiltration. Inflammatory markers, such as iNOS expression and JNK phosphorylation, were also reduced. In mesenteric adipose tissue, infliximab increased the production of IL-10 and resistin, which was associated with the restoration of adipocyte morphology and PPAR-γ expression.

CONCLUSIONS

Our results suggest that infliximab could contribute to the control of intestinal inflammation by modifying adipokine production by mesenteric adipose tissue.

Inflammatory alterations in excluded colon in rats: a comparison with chemically induced colitis

Diversion colitis occurs commonly in the large bowel remnant after diversion of the fecal stream. Several experimental models of colitis have been described, but none examine the inflammatory alterations that can occur in experimentally defunctioned colons. This characterization could be useful in understanding pathophysiological aspects of diversion colitis, and in developing future therapeutic strategies. Thus, we evaluated the temporal inflammatory alterations in the defunctioned colon of rats by analyzing the histological results, infiltrating neutrophils, pro-inflammatory markers such as cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS), and DNA damage in isolated colonocytes. We compared the obtained data with those from hapten-induced colitis. The experimental diversion of the colon fecal stream induces diversion colitis characterized by an early inflammatory process with increased neutrophil infiltrate, and COX-2 and iNOS expression that resembles, in some aspects, the inflammatory characteristics of chemically induced colitis. After acute inflammation resolution, there was an increase in COX-2 and iNOS expression and the presence of lymphoid follicular hyperplasia and ulcerations, suggesting that diversion colitis can be experimentally established and useful for studying different pathophysiological aspects of this condition.