Chemotherapeutic drugs, such as cyclophosphamide, cause severe immunosuppression and patients become susceptible to infections. Based on this, the immunomodulatory potential of tarin, a lectin from Colocasia esculenta, was evaluated in bone marrow cell cultures and in cyclophosphamide-immunosuppressed mice. Tarin promoted maintenance of hematopoietic progenitors and repopulation of Gr1 cells in vitro which was supported by in vivo results. In immunosuppressed mice, tarin increased bone marrow cell numbers and altered cell profile distribution by enhancing the frequency of Gr1+ progenitors, including Ly6-CintLy6-Glo, and anticipating their proliferation/differentiation in mature cells, especially Ly6-CloLy6-Ghi. Bone marrow cells harvested from tarin-treated immunosuppressed mice proliferated in response to GM-CSF or G-CSF in vitro and, the low numbers of bone marrow cells in the G0 phase, combined with a high number cells undergoing apoptosis confirmed that tarin promoted a faster and intense proliferation/differentiation, even in the presence of CY-induced toxicity. As a result, tarin minimized leukopenia in immunosuppressed mice promoting a faster recovery of peripheral leucocytes and protected erythroid bone marrow cells from CY-cytotoxicity in a dose-dependent manner. Data suggest that tarin could be considered a potential adjuvant to decrease leukopenia and possibly ameliorate anemia, if carefully evaluated in human cancer cell lineages and in clinical trials.
Keywords: Research Article; Biology and life sciences; Cell biology; Cellular types; Animal cells; Bone marrow cells; Blood cells; White blood cells; Granulocytes; Immune cells; Immunology; Medicine and health sciences; Research and analysis methods; Animal studies; Experimental organism systems; Model organisms; Mouse models; Animal models; Biochemistry; Proteins; Lectins; Red blood cells; Immune suppression; Diagnostic medicine; Signs and symptoms; Pathology and laboratory medicine; Cell processes; Cell death; Apoptosis
Chemotherapeutic drugs, such as cyclophosphamide (CY), cause severe lymph and myelosuppression, resulting that >10% of the population undergoing chemotherapy becomes susceptible to infections [[
Lectins are proteins or glycoproteins, derived from plants and other organisms, that can be obtained at a relatively low cost and display clinical significance and therapeutic potential, due to their anti-HIV, anti-tumoral, antimicrobial, anti-inflammatory and anti-nociceptive activities [[
Our research group successfully purified to homogeneity (>90%) a lectin from taro (Colocasia esculenta), named tarin, using a simple, replicable, fast, and low-cost procedure [[
In the present study, the potential therapeutic of tarin as an immunomodulatory agent was evaluated in bone marrow cell cultures and in CY-immunosuppressed mice. Tarin allowed the maintenance of hemopoietic progenitor cells favoring the growth of granulocytes in vitro and in vivo. In addition, tarin minimized leukopenia in immunosuppressed mice promoting a faster recovery of peripheral leucocytes and protected erythroid bone marrow cells from CY-cytotoxicity in a dose-dependent manner, suggesting that tarin might be useful as an immunomodulatory adjuvant in therapeutic regimens.
Adult male C57BL/6 mice (8 to 12 weeks old) were provided by the Laboratory Animal Nucleus (NAL), located at the Biology Institute of the Universidade Federal Fluminense (UFF), Brazil. The animals were maintained under conventional environmental conditions with exhaust fans, at a room temperature of 23–25°C, fed with Nuvilab CR-1 chow (Nuvital Nutrientes S/A, Colombo, BRA) and acidified water ad libitum. Research protocol was approved by the Animal Experimentation Ethics Committee (CEPA) at NAL-UFF, under number 670/2016.
Colocasia esculenta (L.) Schott corms were manually chosen and purchased from a local market in Rio de Janeiro, Brazil. The crude taro extract (CTE) was obtained according to Roy, Banerjee, Majumder, & Das [[
The animals were anesthetized with an overdose of 40mg/kg xylasin and 200mg/Kg ketamin and were sacrificed by cervical dislocation. Bone marrow (BM) cells were obtained by percolating the femurs with sterile phosphate buffered saline (PBS). Cell suspensions were washed twice in PBS, centrifuged at 258 × g at 4°C on centrifuge PR-2 (IEC–Co Inc., TN, USA). Pellet cells were subjected to osmotic shock by the addition of a hypotonic solution (5 x diluted PBS with distilled water) to eliminate erythrocytes. A cell sample was diluted in Turk's solution, transferred to a Neubauer chamber (Labor Optik, Lancing, UK), and counted under an optical Olympus BX41 microscope (Olympus America Inc., NY, USA).
Cells were cultured (2 × 10
BM cells were obtained on day 4 from distinct mice groups: CY–mice immunosuppressed with CY 300 mg/kg (Genuxal) (Baxter Hospitalar Ltda, MG, BRA); CY+Tarin—CY-immunosuppressed mice treated concomitantly with 200 μg tarin on day 0; Tarin—mice treated with 200 μg tarin on the same day or Control—mice inoculated with saline. Cells at 2×10
Filgrastine (Blau Farmacêutica S.A., SP, Brazil) was used as source of recombinant human granulocyte colony-stimulating factor (rHu-G-CSF). The cell lines WeHi 3B and MM3 were obtained from the Rio de Janeiro Cell Bank (APABCAM, RJ, Brazil) and their supernatants were also used as a source of IL-3 and GM-CSF, respectively.
To study the effects of tarin administration on the cell cycle and apoptosis, BM cells were obtained from mice on day 4 after as follows: CY–mice immunosuppressed with CY 300 mg/kg; CY+Tarin—CY-immunosuppressed mice treated concomitantly with 200 μg tarin on day 0; Tarin -mice treated with 200 μg tarin on the same day or Control—mice inoculated with saline. The assays were performed according to the protocol established by Riccardi and Nicoletti [[
Cells freshly obtained from BM and from the BM cultures were counted by the exclusion test using Trypan blue to determine cell viability [[
To investigate the effects of tarin on peripheral blood cells of immunosuppressed mice, the following protocol was established. Mice were divided in four groups (n = 4), which intraperitoneally received: i) sterile physiological saline (Control); ii) 200 μg tarin on days 0, 2, and 5 (Tarin); iii) 300 mg/kg cyclophosphamide on day 0 (CY300); and iv) 300 mg/kg cyclophosphamide on day 0, followed by 200 μg tarin on days 0, 2, and 5 (CY300 + Tarin). Blood cell parameters from each group were analyzed during and after treatments, as described in the following.
Anesthetized mice from each group were bled on days 0, 2, 5, and 7 by the retro-orbital plexus, with the aid of a Pasteur pipette, to determine the number of circulating leukocytes and the Hematocrit. Blood sample were transferred to microfuge tubes containing 50μL of heparin (25 UI/mL). Collected blood was diluted 1:100 in Turk's solution, to eliminate erythrocytes, and the number of peripheral blood leukocytes (PBLs) was counted in a Neubauer chamber. For hematocrit measurements, blood was transferred to capillary glass tubes previously treated with heparin 50UI/mL, one of the ends was sealed and the tubes were centrifuged at 715 × g, 4°C for 10 min. Hematocrits were determined by the ratio between the total column height (erythrocytes + plasma) and the erythrocyte column height.
To evaluate the effects of tarin on BM cells from CY-immunosuppressed mice, appropriate assays were conducted as described on previous section, with modifications. In three independent experiments, CY-immunosuppressed mice received 200 μg tarin intraperitoneally: i) after 2 days; ii) after 3 days and iii) after 4 days. The animals were euthanized 24h after tarin exposure. In other set of experiments, CY-immunosuppressed mice received a unique intraperitoneal dose of tarin right after CY inoculation on day 0, and mice were euthanized on days 4, 5, 7 and 9. Mice BM cells from each set of experimental group was removed and cell suspensions were properly prepared and evaluated by flow cytometry and clonogenic assays, as described previously.
To study the effects of tarin administration on erythroid lineage cells of mice submitted to cytotoxicity caused by distinct CY doses, animals were divided into 5 groups. Each group received intraperitoneally: i) CY at 50 mg/kg on day 0 (CY50); ii) CY at 300 mg/kg on day 0 (CY300); iii) CY at 50 mg/kg on day 0 followed by 200 μg tarin on days 0, 2 and 5 (CY50 + Tarin); iv) CY at 300 mg/kg on day 0 followed by 200 μg tarin on days 0, 2 and 5 (CY300 + Tarin); vi) sterile physiological saline (Control).
On the 6th day after treatment, mice from each group (n = 4) were sacrificed after anesthesia by cervical dislocation, the BMs were removed and cell suspensions prepared as previously described, however, in this assays, erythrocytes were not eliminated. Cell samples were smeared on glass slides, dried overnight at room temperature and stained by Leishman staining [[
Multiple comparison analyses were performed by one-way or two-way ANOVA followed by Tukey post-hoc test [[
To investigate the immunomodulatory potential of tarin, mice BM cells were cultured in the presence of tarin and the granulocytes was evaluated by cytospin and flow cytometry. Tarin exhibited protective and stimulatory effects on BM cell cultures, as indicated by the maintenance of the granulocyte ratio to total cells, particularly from day 10 to day 19 (Fig 1A). Control cell cultures in the absence of tarin, at 3 and 6 days, showed a decrease in granulocyte numbers of 20% and 55%, respectively, whereas in the cell cultures, after tarin addition, the number of granulocytes displayed a discrete reduction of 5% and 25%, at the same time periods (Fig 1A). From day 10 to day 19, a drastic reduction in granulocyte counts was observed in the control cultures, where the remaining cells reached 5% of total cells. On the other side, cultures that received tarin were able to maintain a ratio around 45% of granulocytes during the same time period (Fig 1A).
To confirm the stimulatory effects of tarin on myeloid lineage cells, a flow cytometry analysis was performed on the 6
Tarin-treated cells revealed the presence of many fibroblast-like adherent cells and refringent rounded cells with a ring nucleus in the cultures after 6 days, in contrast with that observed in cultures grown in the absence of tarin, where the predominance of subcellular elements (debris) were observed during same time period (Fig 2, top panel). In addition, cells harvested at day 19 presented morphological characteristics of mature granulocytes and also precursor cells of the granulocytic lineage in distinct developmental stages (Fig 2, bottom panel), suggesting that maintenance/differentiation of such cells can occur in vitro induced by tarin stimuli.
Tarin was able to stimulate myeloid BM cells in loco in CY-immunosuppressed mice exposed to tarin on days 2, 3 or 4 (Fig 3A). Tarin administration to immunosuppressed mice caused an increase in the number of BM cells when administered on day 2 or 4, after CY-challenge, recovering control cell levels on such days (Fig 3A). Although the absolute number of cells in the granulocytic region (R1) was not significantly different comparing both groups on the analyzed days, a clear increasing trend was observed (Fig 3B, top panel). On the other hand, the absolute number of cell in the mono/blastic cells region (R2) strongly increased in tarin-treated immunosuppressed mice on day 4 (Fig 3B, bottom panel).
In the other set of experiments, mice concomitantly received CY and tarin and were euthanized after 4, 5, 7 and 9 days. In CY-immunosuppressed mice, the BM cell profile showed a decrease in the granulocytic and an increase in mono/blast cell regions at day 4 (S1 Fig). However, when associated to tarin, an increase in the granulocytic and mono/blast cell regions was observed compared to control mice (S1 Fig). An increment in the Gr1
Further analysis of BM cells from CY-immunosuppressed mice at the granulocytic region (R1), indicated that tarin caused an increase in Ly6-C
To determine if BM cells harvested from tarin-treated immunosuppressed mice after 4 days would be able to proliferate in vitro in response to GM-CSF or G-CSF, colonies and cluster counts were determined in soft-agar culture after 7 days. Immunosuppressed and tarin-treated immunosuppressed mice exhibited a higher number of colonies and clusters compared to the control mice but no difference was observed between them (Fig 5). On the other hand, the number of BM cells in the G0 phase decreased (Fig 6A) and the number of cells undergoing apoptosis increased in immunosuppressed mice exposed to tarin for 4 days (Fig 6B).
The CY-injection caused a drastic reduction in the number of circulating leukocytes soon after drug administration (Fig 7A). However, after tarin administration to CY-immunosuppressed animals, the drops in leukocytes were minimized on days 2 and 5 (4.51 ± 0.9 x 10
Cyclophosphamide caused a dose-dependent increase in the frequency of micronucleated erythrocytes in BM in situ, in accordance to the high cytotoxicity of this drug. On the other hand, tarin administration protected erythroid BM cells from the cytotoxic effects of CY, particularly at CY 50 mg/kg, decreasing the frequency of micronucleated erythrocyte cells to basal levels. A minor protective tarin effect was evidenced at CY 300 mg/kg (Fig 7B).
Immunomodulatory molecules act on immunological components resulting in stimulation, suppression or modulation of the immune system [[
These in vitro effects have been described for other lectins belonging to tarin family, the GNA-related lectins, such as those found in banana, artocarpin, garlic, and dolichos. These lectins are able to promote the maintenance of human and murine cord blood C34
Tarin in vitro stimulatory and protective effects on progenitor hematopoietic cells were supported by in vivo results using the CY-immunosuppressed mice model. The effects of CY on mice reproduced those observed in patients under chemotherapy, where a strong leukopenia is observed [[
BM cell proliferation in response to GM-CSF and G-CSF in CY-immunosuppressed mice and tarin-treated CY-immunosuppressed mice, was quite similar in clusters and colony numbers on the days analyzed. Considering the higher CY toxicological effect on day 3 and the tarin effect on granulocytes at different cellular developmental stages, it is possible that the effects of tarin inoculation may be evidenced in early days and/or in clonogenic cell-type composition. Cell cycle and apoptosis analysis of BM cells from tarin-treated CY-immunosuppressed mice confirmed tarin ability to stimulate cell proliferation. The elevated number of cells under apoptosis in CY-immunosuppressed mice treated with tarin could reflect CY-toxicity combined with tarin stimulation of cell proliferation/differentiation in high levels. Thus, data suggests that tarin could promote faster repopulation and renewal of myeloid cells in emergency.
Regarding that particularly neutrophils play a crucial role in fighting infection [[
Based on the obtained results, it could be inferred that tarin administration in immunosuppressed mice could protect hematopoietic progenitors, especially from granulocytic, and, possibly, erythroid lineages, anticipating proliferation/differentiation and consequent repopulation of BM and the release of novel leucocytes to peripheral blood.
The application of tarin as an adjuvant molecule to minimize CY effects should be considered in tumor-bearing mice models since tumor environments stimulate the abnormal development of Gr1
Considering that chemotherapeutic drugs, including cyclophosphamide, can cause severe lymph and myelosuppression, and that over 10% of patients become susceptible to infections, tarin could be regarded as a promising immunomodulatory adjuvant molecule in chemotherapeutic regimens. Although the results presented here were obtained in a murine model by evaluating in vitro, in vivo and ex vivo tarin effects, for tarin, to be considered as a potential adjuvant, it should be carefully evaluated in human cancer cell lineages and in clinical trials.
Tarin exhibits potential immunomodulatory properties, with the ability to protect granulocytic progenitor cells and promote their in vitro repopulation. In an immunosuppressed murine model, tarin led to the increased total BM cells and altered the BM cell profile distribution, enhancing the frequency of granulocytic progenitors (Ly6-C
S1 Fig. BM cells distribution profile. Size and granularity parameters of BM cells from: CY–CY-immunosuppressed mice; CY+Tarin—CY-immunosuppressed mice treated concomitantly with 200 μg Tarin on day 0; Tarin—mice treated with 200 μg tarin on the same day or Control—mice inoculated with saline. BM cells were evaluated by flow cytometry on day 4. Dot plots are representative of cell distribution profile of each group. A frequency of cells in granulocytic, mono/blastic and lymphocytes gate were expressed as means ± standard deviation of three independent experiments (n = 3). ***p< 0.001 and ****p<0.0001 compared to Control. # p< 0.05 compared to CY. (TIFF)
S2 Fig. Hematocrit analysis. Blood samples were collected on days 0, 2, 5, and 7 from groups: CY–CY-immunosuppressed mice on day 0; CY + Tarin–CY-immunosuppressed mice treated with 200 μg tarin on day 0, 2 and 5; Tarin–mice treated with 200 μg tarin on days 0, 2, and 5; and Control–mice inoculated with saline. Results are expressed as means ± standard deviation of three independent experiments (n = 3). (TIFF)
DIAGRAM: Fig 1: Protective and stimulatory effects of tarin in mouse bone marrow cell cultures. (A) Granulocyte frequency on days 3, 6, 10, 13, 16, and 19 from the mouse BM cells cultured with 20 μg/mL tarin. Cultures without tarin addition were used as control. (B) Cell distribution profile of the BM cells on 6th day of culture with and without tarin addition (top panels). Frequency of Gr1+ cells on the cultures from BM cells on 6th day of culture are indicated on the histogram plots (bottom panels). Data were obtained from n = 3 experiments. *indicates significance level. *** p<0.001 and ** p< 0.01, compared to control.
DIAGRAM: Fig 2: Morphological characteristics of bone marrow cells cultured with tarin. BM cell cultures incubated with tarin 20 μg/mL (Tarin) and without tarin (Control) for 6 days (top panels) and 19 days (bottom panels). The white arrow indicates a typical nucleus of a myeloid cell in development. The bottom panel shows granulocytic lineage cells in distinct developmental stages in tarin-treated cells (right-hand side) or the control group (left-hand side). Photomicrographs were acquired by an inverted-phase microscopy under 400x magnification (top panel) or by visualization of cytosmears, stained by May-Grunwald Giemsa, using optical microscopy under 200x magnification (bottom panel).
DIAGRAM: Fig 3: Tarin effects on bone marrow cell numbers. (A) Total BM cell numbers from: CY- CY-immunosuppressed mice; CY+Tarin—CY- immunosuppressed mice treated with 200 μg tarin; Tarin—mice treated with 200 μg tarin or Control–mice inoculated with saline. Mice BM cells were evaluated after 24h tarin treatment on days 2, 3 or 4. (B) Dot plots on the left-hand panel represent cell distribution profile (size vs granularity) from healthy BM cells by flow cytometry. The R1 region corresponds to granulocytic lineage cells, while R2 corresponds to mononuclear/blastic cells based on cell size and granularity. Right-hand panels show the total number of cells in R1 and R2 from mice BM treated by the aforementioned protocol. ****p<0.0001, ***p<0.001 and ** p<0.01, compared to control. #p<0.05, ###p< 0.001 or ####p< 0.0001 compared to CY group.
DIAGRAM: Fig 4: Frequency of granulocytic cells in the bone marrow of CY-immunosuppressed mice treated with tarin. (A) Frequency of Gr1+ cells in the BM of CY-immunosuppressed mice treated with a unique dose of 200 μg tarin right after CY-challenge (day 0). Analyses were performed 5, 7 and 9 days after tarin inoculation and cells corresponding to R1 (indicated on ) were evaluated. ****p<0.0001 or *p<0.05 compared to control group. ###p<0.001 or ####p<0.0001 compared to CY group. (B) Dot plot representing Gr1 and c-kit expression on R1 of BM cells from each mice group, as defined in legend, on the 4th day after tarin administration (top panel). Histograms in the bottom panel show Gr1 expression intensity in the same region. (C) Dot plot of Ly6-G and Ly6-C cell markers expression on R1 and R2 of BM cells from distinct mice groups. Ly6-CintLy6-Glo cells are shown in “a” rectangle and Ly6-CloLy6-Ghi cells are shown in “b” rectangle. Data are representative of three independent experiments (n = 3).
DIAGRAM: Fig 5: Clonogenic potential of bone marrow myeloid progenitors. Number of colony-forming units (CFU) and clusters in soft-agar culture of BM cells from: CY–CY-immunosuppressed mice; CY+Tarin—CY-immunosuppressed mice treated concomitantly with 200μg tarin on day 0; Tarin—mice treated with 200 μg tarin on the same day or Control—mice inoculated with saline. BM cells were collected on day 4 and plated with GM-CSF or G-CSF stimuli. Responses to GM-CSF (A) and to G-CSF (B) were analyzed on the 7th day. Results are expressed as the mean values and standard errors of three independent experiments. *p<0.05, ****p<0.0001 compared to the control group.
DIAGRAM: Fig 6: Tarin effects on bone marrow cell proliferation and death. Cell cycle (A) and apoptosis (B) analyses of BM cells from: CY–CY-immunosuppressed mice; CY+Tarin—CY-immunosuppressed mice treated concomitantly with 200 μg tarin on day 0; Tarin—mice treated with 200 μg tarin on the same day or Control—mice inoculated with saline. BM cells were evaluated by flow cytometry on day 4. *p< 0.05, **p< 0.01 and **** p<0.0001 compared to control group. #p< 0.05 compared to CY group.
DIAGRAM: Fig 7: Tarin reduces cytotoxic effects in CY-immunosuppressed mice. (A) Leukocytes number in peripheral mice blood treated with: CY–CY-immunosuppressed mice; CY + Tarin–CY-immunosuppressed mice treated with 200 μg tarin on day 0, 2 and 5; Tarin–mice treated with 200 μg tarin on days 0, 2, and 5; and Control–animals inoculated with saline. Blood samples were collected on days 0, 2, 5, and 7. ***p<0.001 represents Tarin vs Control comparison on day 2, and CY + Tarin vs CY on day 5. *p< 0.05 compares CY + Tarin to CY on day 2. (B) Occurrence of micronuclei in BM erythroid cells from: CY300—mice immunosuppressed with 300 mg/kg CY; CY50—mice immunosuppressed with 50 mg/kg; CY300 + Tarin—mice immunosuppressed with 300 mg/kg and treated with 200 μg tarin and CY50 + Tarin—mice immunosuppressed with 50 mg/kg and treated with 200 μg tarin. ***p<0.001 compared to control;°°°p< 0.001 compared CY50 to CY50+Tarin, and #p< 0.05 compared CY300 to CY300+Tarin.
The authors would like to thank Dr. Tatiana El Bacha Porto, professor at the Federal University of Rio de Janeiro (Universidade Federal do Rio de Janeiro—UFRJ), Brazil, for her valuable contribution in the data interpretation, Dr. Jussara Machado Lagrota Candido, professor at Fluminense Federal University (Universidade Federal Fluminense–RJ), Brazil, for the antibody donation and Dr. Fabio Barrozo do Canto, professor at Fluminense Federal University (Universidade Federal Fluminense–RJ), Brazil, for the help with flow cytometry data acquisition.
By Lyris A. D. Mérida, Writing – review & editing; Érika B. A. Mattos, Writing – review & editing; Anna C. N. T. F. Corrêa, Writing – original draft; Patricia R. Pereira, Writing – review & editing; Vania M. F. Paschoalin, Writing – review & editing; Maria F. B. Pinho, Writing – review & editing and Mauricio A. Vericimo, Writing – review & editing