Improvement Of Peripheral Blood In Mice With Bone Marrow Suppression By Hydrogen Sulfide And Its Mechanism

Hydrogen sulfide (H2S) is a colorless, water soluble, flammable gas that has the characteristic smell of rotten eggs. H2S has traditionally been considered to only be a highly toxic gas like other members of the gasotransmitter family (nitric oxide and carbon monoxide). Recent research indicate that many mammalian cells can often produce H2S under physiological condition. Endogenous H2S is synthesized from L-cysteine mainly by two enzymes, cystathionine β-synthase (CBS) and cystathionine y-lyase (CSE). In the cardiovascular system, CSE is the main H2S-synthesizing enzyme. Whereas CBS enzyme mainly exists in the nervous system. It is reported that endogenous H2S has many physiological function. In cardiovascular system, H2S can relax smooth cells and decrease the blood pressure by activating ATP-dependent K+channels (KATP)-H2S can also mediate cytoprotection by reducing oxidative stress, inhibiting apoptosis, protecting mitochondria. Endogenous H2S is involved in physiological regulation of cardiovascular system, digestive system, nervous system and immune system. H2S is regarded as third gasotransmitters together with nitric oxide (NO) and carbon monoxide (CO).Angiogeneses is formation of new blood vessels from pre-existing vessels. Angiogeneses take part in many physiological or pathological process, it can act positive function (such as ischemia disease) or negative function (such as tumorigenesis). H2S has been identified for the first time by our group that it can stimulate angiogenesis and the proangiogenic effect of H2S is dependent on the phosphorylation of Akt. Endothelial progenitors cells (EPC) have the capacity to proliferate, migrate, and differentiate into endothelial lineage cells in vivo or in vitro. EPCs are defined as CD34+/Flk-1+, CD117+/Flk-1+or CD34+/CD117+/Flk-1+cells. Endothelial progenitor cells circulate in the blood and play an important role in the formation of new blood vessels under physiological condition as well as pathological condition. For these reasons, EPCs play important role in many disease process such as cardiovascular disease, organ transplantation, tumorigenesis. Our hypothesis is that H2S may stimulate angiogenesis through its influence towards EPCs.We used flow cytometry to detect the effect of H2S donor NaHS on bone marrow cells from normal mice. The effect of H2S caused no change in the percentage of EPCs for7days or2days. But we found accidentally a significant increase in the percentage of CD34+cells, CD117+cells and CD34+/CD117+cells after2days’ administration of50μmoL/kg/d NaHS. BrdU uptake analysis revealed that NaHS (30μmoL/L) treatment could promote cell proliferation of primary cultured bone marrow cells. BrdU analyses also suggested that administrating50μmoL/kg/d NaHS for2days caused a significant increase in the percentage of proliferating CD34+and/or CD117+stem cells.CD34+and/or CD117+cells are always defined as hematopoietc stem cells (HSC). H2S can promote the proliferation of CD34+cells, CD117+cells and CD34+/CD117+cells. Dose it means H2S can regulate haematogenesis through affecting hemato-poietc stem cells? Till now, there is no report about the relationship between H2S and haematogenesis. The purpose of the present study is to assess the protect role of H2S using the myelosuppressive model.First, myelosuppressive mice model was established by carboplatin treatment and radiation. The influence of H2S on peripheral blood cells was then investigated under myelosuppression. The effect of NaHS (10,50,100μmoL/kg/d) and recombinant human granulococyte-macrophage colony stimulating factor (rhG-CSF) was assessed2days,7days,14days,21days and28days after administrating. We detected peripheral erythrocytes, platelets and leukocytes count and peripheral hemoglobin. The results indicate that NaHS administrating can improve the recovery of peripheral blood cells under myelosuppressive condition and50μmoL/kg/d NaHS is the most efficient dosage.Peripheral erythrocyte count and peripheral hemoglobin decreased slowly with2days’ administration of50μmoL/kg/d NaHS than control group. Peripheral platelets count was significant higher with7and14days’administration of50μmoL/kg/d NaHS than NaCl group. Peripheral leukocytes count was significant higher with14and21days’administration of50[μmoL/kg/d NaHS than NaCl group too. These effect were in a time-dependent manner. Values are mean±SE.*P<0.05. These data suggestes that H2S can improve the recovery of peripheral blood cells from myelosuppressive mice to some extent.Furthermore, we investigated the mechanisms of the protect effect of H2S in improving the recovery of peripheral blood cells under myelosuppression. The results indicate that NaHS administration can increase the proportion of bone marrow CD34+, CD117+, CD34+/CD117+cells and50μmoL/kg/d NaHS is the most efficient dosage. Administrated NaHS50μmoL/kg/d2days,7days,14days and21days, bone marrow CD34and CD117positive cells number was significant higher than NaCl group. This effect of H2S was in time-dependent manner. Administrated NaHS50μmoL/kg/d2days,7days and14days, bone marrow CD34/CD117positive cells number was significant higher than NaCl group as well as before. Meanwhile, after14days,21days and28days administration, the ratio of spleen weight and body weight of NaHS50μmoL/kg/d group was significant higher than NaCl group too. This effect of H2S was also in time-dependent manner.Administrated NaHS50μmoL/kg/d, NaHS100μmoL/kg/d and rhG-CSF2days, the percentage of apoptosis showed a significant decrease than NaCl group. This result indicates that H2S can reduce the percentage of apoptosis of bone marrow cells. Administrated NaHS50μmoL/kg/d7days, the number of cells in G0/G1phase showed a significant decrease than NaCl group. On the countrary, the number of cells in G2/M and S phase of NaHS50μmoL/kg/d group was significant higher than NaCl group. Values are mean±SE.*P<0.05,**P<0.01. This result suggest that H2S may promote bone marrow cells mitochysis under myelosuppressive condition.In summary, the present study provides the first evidence that H2S can improve the recovery of peripheral blood cells under myelosuppressive condition. This effect probably relates to the increasement in bone marrow CD34+, CD117+, CD34+/CD117+cells proliferation; spleen protection; apoptosis reduction; mitochysis promotion and so on.