Peroral IMUNOR, a low-molecular-weight immunomodulator prepared from disintegrated and ultrafiltered leukocytes, enhances recovery from myelosuppression induced by cisplatin or 5-fluorouracil

Myeloprotective effects of C-type natriuretic peptide on cisplatin-induced bone marrow granulocytopenia in mice

PURPOSE

Cisplatin is an effective chemotherapeutic agent used to treat a variety of malignant tumors. The major toxicity associated with cisplatin treatment is granulocytopenia. C-type natriuretic peptide (CNP), a member of the natriuretic peptide family, protects against toxicity in many organs, including the heart, blood vessels, lung, and kidney. The objective of this study was to investigate the myeloprotective effects of CNP in a mouse model of cisplatin-induced granulocytopenia.

METHODS

The mice were divided into two groups: cisplatin with vehicle and cisplatin with CNP. CNP (2.5 μg/kg/min via osmotic pump, subcutaneously) or vehicle administration was started two day before cisplatin injection, and continued until the mice were killed. At 0, 2, 4, 8, and 14 days after cisplatin injection (16 mg/kg, intraperitoneally as a single dose), we counted total and living cells and granulocyte/macrophage colony-forming units (CFU-GM) in bone marrow. In addition, at 0, 1, 2, and 4 days after cisplatin injection, we measured mRNA levels of CXC chemokine receptor 4 (CXCR4) and chemokine CXC ligand 12 (CXCL12) in bone marrow.

RESULTS

CNP significantly attenuated the reduction in bone marrow nucleated cell count and CFU-GM in bone marrow at 4 days after cisplatin injection. Four days after cisplatin injection, CNP significantly decreased the CXCR4 mRNA level in bone marrow, but had no effect on the level of CXCL12 mRNA.

CONCLUSIONS

CNP exerts myeloprotective effects in cisplatin-induced granulocytopenia and decreases CXCR4 expression.

Ultrafiltered pig leukocyte extract (IMUNOR®) decreases nitric oxide formation and hematopoiesis-stimulating cytokine production in lipopolysaccharide-stimulated RAW 264.7 macrophages

A low-molecular-weight (<12 kDa) ultrafiltered pig leukocyte extract, IMUNOR, was tested in experiments in vitro on non-stimulated and lipopolysaccharide (LPS)-stimulated murine RAW 264.7 macrophages in order to assess modulation of nitric oxide (NO) production (measured indirectly as the concentration of nitrites), hematopoiesis-stimulating activity of the supernatant of the macrophage cells (ascertained by counting cell colonies growing from progenitor cells for granulocytes and macrophages (GM-CFC) in vitro), and the release of hematopoiesis-stimulating cytokines. No hematopoiesis-stimulating activity and cytokine or NO production were found in the supernatant of non-stimulated macrophages. It was found that IMUNOR does not influence this status. Supernatant of LPS-stimulated macrophages was characterized by hematopoiesis-stimulating activity, as well as by the presence of nitrites, interleukin-6 (IL-6), and granulocyte colony-stimulating factor (G-CSF). A key role in the hematopoiesis-stimulating activity of the supernatant of LPS-stimulated macrophages could be ascribed to G-CSF since the formation of the colonies could be abrogated nearly completely by monoclonal antibodies against G-CSF. IMUNOR was found to suppress all the mentioned manifestations of the LPS-activated macrophages. When considering these results together with those from our previous in vivo study revealing stimulatory effects of IMUNOR on radiation-suppressed hematopoiesis, a hypothesis may be formulated which postulates a homeostatic role of IMUNOR, consisting in stimulation of impaired immune and hematopoietic systems but also in cutting back the production of proinflammatory mediators in cases of overstimulation which threats with undesirable consequences.

The role of G-CSF and IL-6 in the granulopoiesis-stimulating activity of murine blood serum induced by perorally administered ultrafiltered pig leukocyte extract, IMUNOR®

IMUNOR, a low-molecular weight (< 12 kD) ultrafiltered pig leukocyte extract, has been previously found to have significant stimulatory effects on murine hematopoiesis supressed by ionizing radiation or cytotoxic drugs. This communication shows data on the mechanisms of these effects. Using ELISA assay, significantly increased levels of granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6) were observed. On the contrary, no detectable levels of granulocyte-macrophage colony-stimulating factor (GM-CFC) and interleukin-3 (IL-3) have been found in blood serum of IMUNOR-treated mice. Incubation of the serum from IMUNOR-treated mice with antibodies against G-CSF caused abrogation of the ability of the sera to stimulate in vitro growth of colonies originating from granulocyte-macrophage progenitor cells (GM-CFC). In contrast, incubation of the serum with antibodies against IL-6 did not change its colony-stimulating activity. It may be inferred from these findings that G-CSF is probably the main cytokine responsible for the granulopoiesis-stimulating effects of IMUNOR. When the serum from IMUNOR-treated mice with G-CSF inactivated by anti-G-CSF antibodies (but with elevated IL-6) was added to cultures of bone marrow cells together with a suboptimum concentration of IL-3, a significant increase in the numbers of GM-CFC colonies was found. Moreover, conjoint inactivation of G-CSF and IL-6 significantly decreased the numbers of GM-CFC colonies in comparison with those observed when only G-CSF was inactivated. This observation strongly suggests that though IMUNOR-induced IL-6 is not able to induce the growth of GM-CFC colonies alone, it is able to potentiate the hematopoiesis-stimulating effect of IL-3. These findings represent a new knowledge concerning the hematopoiesis-stimulating action of IMUNOR, a promising immunomodulatory agent.