Israel Medical Association Journal

Background: Chronic nicotine administration has a dual effect on inflammatory bowel disease: augmentation of jejunitis and amelioration of colitis. We previously showed that chronic nicotine administration has divergent regional effects on small bowel and colonic mucosal mediators and blood flow.

Objective: To examine the effects of nicotine administration on cytokine levels in normal rat small bowel mucosa, colonic mucosa, and blood.

Methods: Male Sprague-Dawley rats weighing 200–250 g were given nicotine (12.5 μg/ml) that was dissolved in tap water. Rats were sacrificed on days 1, 2, 7 and 14 after nicotine initiation; blood was withdrawn, and small bowel and colon were resected, washed and weighed. Mucosal scrapings were extracted in 2 ml Krebs-Hemselest buffer for determination of interleukins-2, 6 and 10 using the Biosource International Immunoassay Kit.

Results: Nicotine decreased IL-10[1] and increased IL-6 levels in small bowel mucosa (from 3.5 ±  0.5 to 0.4 ± 0.1 pg/ml and from 1.9±0.4 to 13.6±0.4 pg/ml respectively; P < 0.05). Nicotine decreased IL-2 levels in the colon (from 15.8±3.0 to 7.9±1.0 pg/ml; P < 0.05), having no effect on IL-10 or IL-6 levels. Rats treated with nicotine had lower IL-6 and IL-2 blood levels compared to control rats.

Conclusions: Nicotine has different regional effects on small bowel and colonic cytokine mucosal levels, which might explain some of its opposite effects on small bowel and colonic inflammation.

Background: Inflammatory mediators, including cytokines and reactive oxygen species. are associated with the pathology of chronic liver disease. Hepatocytes are generally considered as targets but not producers of these important mediators.

Objectives: To investigate whether cells of hepatocellular lineage are a potential source of various cytokines we estimated the expression and secretion of tumor necrosis factor alpha, transforming growth factor beta 1 and interleukins I beta, 6 and 8 in the culture of well-differentiated human HepG2 cells treated for 24 hours with ethanol, acetaldehyde and lipopolysaccharide. Lipid peroxidation damage, glutathione content and glutathione perox­idase, catalase and superoxide dismutase activity were also determined.

Methods: HepG2 cells were treated for 24 hours with ethanol (50 mM), acetaldehyde (175 ìM) and LPS (1 ìg/ml). TNF-á, TGF­-â, L-1â, IL-6 and IL-8 mRNA were determined by reverse transcriptase polymerase chain reaction and secretion by en­zyme-linked immunoassay. Lipid peroxidation damage, glutathione content and antioxidant enzyme activities were determined spectrophotometrically.

Results: Exposure to ethanol for 24 hours induced the expression of TNF-á and TGF- â1. secretion of IL-1â and TGF-â₁ and decreased catalase activity. Acetaldehyde markedly increased TNF-á and IL-8 expression, stimulated IL-1â and IL-8 secretion, increased lipid peroxidation damage and decreased catalase activity, while LPS exposure induced the expression of TNF-á. TGF- â₁, IL-6 and IL-8, the secretion of TGF-â₁, IL-1â, IL-6 and IL-8, and a decrease in catalase activity. No change in GSH, GSHPx or SOD was found in any experimental condition.

Conclusions: The present studies confirm and extend the notion that hepatocytes respond to ethanol, acetaldehyde and LPS-producing cytokines. Oxidative stress produced by the toxic injury plays an important role in this response through up­regulation of inflammatory cytokines.

Background: Exposure of newborn animals to high concentrations of oxygen leads to diffuse alveolar damage similar to that seen in bronchopulmonary dysplasia in human infants. Therefore, neonatal rats are a suitable practical model of hyperoxic lung damage in human infants.

Objective: To determine the involvement of tumor necrosis factor-alpha and interleukin-6 in lung injury in neonatal rats exposed to 100% O2 concentration.

Methods: A randomized controlled study was designed in which litters of term Sprague-Dawley rat pups were assigned to experimental or control groups. The pups in the experimental group were placed in 100% O2 from birth for 9 days, while the control pups were placed in room air. Twelve to 15 pups from each group were sacrificed on day 1, 3, 6, 9 and 13 after birth for bronchoalveolar lavage collection and lung histologic study. The bronchoalveolar lavage fluid was assayed for TNFα and IL-6.

Results: Newborn rats exposed to 100% O2 for the first 9 days of life showed severe pulmonary edema and hypercellularity on days 1 and 3, which then improved to nearly complete resolution on days 6 and 9. Pulmonary TNFα was produced early on O2 exposure (day 3) and pulmonary IL-6 later (days 6 and 9).

Conclusions: Hyperoxia induces sequential production of pulmonary TNFα and IL-6, which corresponds to the severity of the pathological findings and the known inflammatory and anti-inflammatory role of these cytokines.

________________________________

TNFα= tumor necrosis factor-alpha

IL-6= interleukin-6

Background: Cell-mediated immunity is impaired in uremia. Cell-matrix interactions of immune cells such as CD4+T lymphocytes with extracellular matrix are an important requirement for an intact immune response. The adherence of CD4+T cells of healthy subjects (normal T cells) to ECM components is inhibited in the presence of uremic serum. Such decreased adhesive capacity is also found in T cells of dialysis patients. Various chemokines and cytokines affect the attachment of CD4+T cells to ECM.

Objective: To evaluate chemokine (MIP-1β and RANTES) and tumor necrosis factor α-induced adhesion of CD4+T cells to ECM in a uremic milieu.

Methods: We examined adhesion of normal CD4+T cells (resting and activated) to intact ECM in response to soluble or bound chemokines (MIP-1β and RANTES) and to TNF-α following incubation in uremic versus normal serum. Thereafter, we evaluated the adhesion of resting CD4+T cells from dialysis patients in a similar fashion and compared it to that obtained from a healthy control group.

Results: Addition of uremic serum diminished soluble and anchored chemokine-induced attachment of normal resting and activated CD4+T cells to ECM compared to a normal milieu (a peak response of 10–11% vs. 24–29% for soluble chemokines, P<0.001; 12–13% vs. 37–39% for bound chemokines on resting cells, P<0.01; and 18–20% vs. 45–47% for bound chemokines on activated cells, P<0.02). The same pattern of response was noted following stimulation with immobilized TNF-α (7 vs. 12% for resting cells, P<0.05; 17 vs. 51% for activated cells, P<0.01).  Adherence of dialysis patients’ cells to ECM following stimulation with both bound chemokines was reduced compared to control T cells (15–17% vs. 25–32%, P<0.0000). In contrast, adherence following stimulation by TNF-α was of equal magnitude.

Conclusions: Abnormal adhesive capacity of T lymphocytes to ECM in uremia may, in part, be related to a diminished response to MIP-1β, RANTES and TNF-α. However, whereas reduced adhesion to chemokines was present in both normal CD4+T cells in a uremic environment and in dialysis patients’ T cells, TNF-α-induced adhesion was found to be inhibited only in normal cells in a uremic milieu.

____________________________

ECM = extracellular matrix

TNF-α = tumor necrosis factor-a