Species specificity at the molecular level: the case of nitric oxide synthases

Macrophages influence gap junctional intercellular communication between smooth muscle cells in a co-culture model

The present study demonstrates for the first time that cells cultured on pore membrane inserts (macrophages) modulate gap junctional intercellular communication (GJIC) between a second cell type (smooth muscle cells (SMC)) co-cultured in Transwell-COL cell culture chambers. Unstimulated J774A.1 murine macrophages reduced GJIC between human SMC. Stimulation of J774A.1 cells by lipopolysaccharide (LPS) or interferon-γ abrogated this modulation of GJIC. Unstimulated human monocyte-macrophages did not affect GJIC between human SMC. Upon stimulation of these monocyte-macrophages with LPS, a substantial increase in GJIC between co-cultured SMC was observed. Thus, activation of macrophages alters their interaction with co-cultured SMC. Since these results were obtained in an indirect co-culture system in which direct cell-cell contact is prevented, it is hypothesized that soluble factors released by macrophages may be involved in this modulation of GJIC between SMC. The possible nature of the responsible soluble factors is discussed in the context of atherosclerosis.

Nitric oxide production in critically ill patients

OBJECTIVE

To measure serum nitrite and nitrate levels in critically ill children as indicators of endogenous nitric oxide (NO) production.

HYPOTHESIS

Endogenous NO production is increased in children with conditions characterised by immune stimulation.

DESIGN

Prospective descriptive study in a multidisciplinary paediatric intensive care unit.

PATIENTS

137 consecutive critically ill children with a variety of clinical conditions.

INTERVENTIONS

Using a rapid microtitre plate technique, daily serum nitrite and nitrate levels were measured from serum samples that remained in the clinical laboratory after daily routine phlebotomy. Clinical and laboratory information was also gathered daily for each patient.

RESULTS

The maximum serum nitrite plus nitrate levels (microM) reached by children with infection (41.8 (SD 18.1)), sepsis syndrome (85.1 (39.9)), shock without sepsis (36.4 (19.1)), transplantation alone (61.0 (43.4)), transplantation with sepsis (200.7 (150.5)), or rejection (161.7 (70.4)), were higher than in controls (18.1 (9.3)). In the absence of exogenous NO donors, levels greater than 80 microM were reached only in children with the sepsis syndrome, organ transplantation, or acute rejection.

CONCLUSIONS

Increased endogenous NO production occurs in children with clinical conditions associated with immune stimulation. Further investigation is warranted to determine the value of this simple and rapid test as a clinically useful diagnostic tool and therapeutic monitor in the evaluation of children at risk for the sepsis syndrome or acute allograft rejection.