Immunotoxicity and allergic potential induced by topical application of dimethyl carbonate (DMC) in a murine model

Figures & data

Figure 1.  Chemical structure of DMC.

Figure 2.  Irritancy and allergic sensitization potential after dermal exposure to DMC. Analysis of the (a) irritancy and (b) allergic sensitization potential of DMC using the combined irritancy/LLNA. DPM represent [³H]-thymidine incorporation into draining lymph node cells of BALB/c mice following exposure to vehicle or concentration of DMC. Bars represent mean (± SE) of five mice (10 ears; irritancy) per group. Levels of statistical significance are denoted (** p < 0.01) as compared to acetone vehicle.

Table 1.  Body/organ weights of female B6C3F1 mice dermally exposed to dimethyl carbonate for 28 days.

Parameter	Dimethyl carbonate
	0%	50%	75%	100%
Body weight (g)	21.61 ± 0.40	20.79 ± 1.10	22.33 ± 1.17	22.07 ± 1.02
Kidney weight (mg)	259 ± 5	264 ± 18	284 ± 15	272 ± 9
% bw	1.19 ± 0.01	1.27 ± 0.03	1.28 ± 0.08	1.23 ± 0.00
Spleen weight (mg)	88 ± 17	75 ± 5	74 ± 4	67 ± 4
% bw	0.41 ± 0.09	0.36 ± 0.01	0.33 ± 0.02	0.30 ± 0.02
Thymus weight (mg)	55 ± 2	50 ± 2	44 ± 3*	40 ± 3**
% bw	0.26 ± 0.01	0.24 ± 0.02	0.20 ± 0.02	0.18 ± 0.02*
Liver weight (mg)	1123 ± 74	1013 ± 65	1090 ± 62	1034 ± 60
% bw	5.20 ± 0.38	4.90 ± 0.07	4.90 ± 0.31	4.70 ± 0.15

bw, body weight.

Values are expressed as means (± SE) for each group.

Significantly different from acetone controls at * p < 0.05 or ** p < 0.01.

Table 2.  Hematology parameters of female B6C3F1 mice dermally exposed to dimethyl carbonate for 28 days.

Parameter	Dimethyl carbonate
	0%	50%	75%	100%
Hemoglobin (g/dl)	13.84 ± 0.26	12.82 ± 0.79	13.50 ± 0.63	13.84 ± 0.76
Erythrocytes (M/μl)	8.96 ± 0.22	8.35 ± 0.50	8.59 ± 0.43	8.85 ± 0.50
Platelets (K/μl)	291 ± 131	471 ± 92	297 ± 101	384 ± 63
Hematocrit (%)	47.36 ± 1.05	43.74 ± 2.79	44.68 ± 2.26	46.40 ± 2.78
MCV (fl)	52.84 ± 0.21	52.32 ± 0.30	52.02 ± 0.12	52.40 ± 0.27
MPV (fl)	5.66 ± 0.32	5.52 ± 0.65	5.28 ± 0.44	4.80 ± 0.28
MCH (pg)	15.46 ± 0.12	15.36 ± 0.12	15.70 ± 0.17	15.68 ± 0.11
MCHC (g/dl)	29.22 ± 0.21	29.32 ± 0.19	30.26 ± 0.35	29.88 ± 0.24
PDW (%)	23.02 ± 1.06	20.24 ± 1.09	22.80 ± 1.81	22.86 ± 1.13
Leukocytes (K/μl)	7.00 ± 1.34	6.64 ± 1.51	7.75 ± 1.42	7.26 ± 1.37
% Lymphocytes	74.62 ± 2.50	73.90 ± 3.08	81.94 ± 1.15	73.87 ± 3.48
% Neutrophils	20.39 ± 1.95	20.39 ± 2.29	14.93 ± 1.15	21.44 ± 2.13
% Monocytes	3.76 ± 0.31	3.81 ± 0.37	2.57 ± 0.33	2.80 ± 0.42
% Eosinophils	1.09 ± 0.37	1.57 ± 0.55	0.69 ± 0.20	1.37 ± 0.85
% Basophils	0.15 ± 0.05	0.34 ± 0.13	0.07 ± 0.03	0.52 ± 0.31

MCH, mean corpuscular hemoglobin; MCV, mean corpuscular volume; MPV, mean platelet volume; PDW, platelet distribution width; MCHC, mean corpuscular hemoglobin concentration.

Values are expressed as the means (± SE) for each group.

Table 3.  Effects of dermal exposure to dimethyl carbonate for 28 days on total spleen cell number and of lymphocyte sub-populations in female B₆C₃F₁ mice.

Parameter	Dimethyl carbonate
	0%	50%	75%	100%
Spleen nucleated cell number (×10^6)	143.6 ± 17.10	116.2 ± 4.6	123.4 ± 4.8	113.6 ± 7.3
B-cell number (×10^6)	66.37 ± 7.7	55.92 ± 3.5	63.53 ± 2.3	54.75 ± 4.7
% of splenocytes	46.30 ± 0.89	47.97 ± 1.22	51.57 ± 1.28	47.96 ± 1.10
T-cell number (×10^6)	40.18 ± 1.4	37.48 ± 1.4	38.06 ± 1.2	36.80 ± 1.9
% of splenocytes	27.94 ± 0.31	27.88 ± 0.81	26.18 ± 0.73	27.47 ± 1.13
CD4^+T-cell number (×10^6)	30.18 ± 1.43	27.48 ± 1.40	28.06 ± 1.23	26.80 ± 1.86
% of splenocytes	21.61 ± 1.32	23.77 ± 1.27	22.71 ± 0.47	23.66 ± 0.97
CD8^+T-cells (×10^6)	15.42 ± 0.81	13.80 ± 0.60	13.00 ± 0.29	13.44 ± 1.01
% of splenocytes	11.03 ± 0.66	11.93 ± 0.38	10.58 ± 0.36	11.86 ± 0.53

Mice were dermally exposed to vehicle (acetone) or different concentrations of DMC for 28 days (times) over 2 weeks. The mice were euthanized 24 h after the final exposure, spleens were removed, and total nucleated splenocytes counted. Numbers of B- and T-cells, and subsets of T-cells (CD4⁺ and CD8⁺) were enumerated.

Values represent the means (± SE) for each group.

Figure 3.  DMC suppresses the spleen IgM response to SRBC. Analysis of antibody producing spleen cells after a 28-day dermal exposure to DMC suppressed the (a) total and (b) specific activity IgM response to SRBC. Bars represent mean fold-change (± SE) of six mice per group. Cyclophosphamide (CP) was included as the positive control.

Figure 4.  DMC exposure does not alter the serum IgM response to SRBC. Analysis of serum after a 28-day dermal exposure to DMC did not produce alternations in IgM response to SRBC. Bars represent mean fold-change (± SE) of six mice per group. Cyclophosphamide (CP) was included as the positive control.