Chromium in Stainless Steel Welding Fume Suppresses Lung Defense Responses Against Bacterial Infection in Rats

Figures & data

TABLE 1 Concentrations of welding fume sample (mg/instillate)

Sample	Fe	Cr	Mn	Ni
MMA-SS
Insol metal	0.82	0.09	0.13	0.06
Sol metal	n.d.	0.60	0.04	n.d.

Note. n.d. = below level of detection. Metals were measured in the insoluble (insol) and soluble (sol) fractions of the MMA-SS sample. It is important to note that trace amounts of several other elements were present in the fume.

FIG. 1 Pulmonary clearance of bacteria by rats pre-exposed to (A) 2 mg of manual metal arc, stainless steel (MMA-SS) welding fume or (B) 0.82 mg insoluble Fe₂O₃, 0.60 mg soluble Cr₂Na₂O₇, or 0.06 mg insoluble NiO alone or in combination. The MMA-SS and metal samples were intratracheally instilled 3 days prior to intratracheal inoculation with 5 × 10³ L. monocytogenes. Control animals were pretreated with saline. Values are means in Log₁₀ base units ± standard error of measurement (n = 4–12); *significantly greater than corresponding saline control at each timepoint (p < 0.05).

FIG. 2 Percent change in body weight of rats pre-exposed to (A) 2 mg of manual metal arc, stainless steel (MMA-SS) welding fume or (B) 0.82 mg insoluble Fe₂O₃, 0.60 mg soluble Cr₂Na₂O₇, or 0.06 mg insoluble NiO alone or in combination. The MMA-SS and metal samples were intratracheally instilled 3 days prior to intratracheal inoculation with 5 × 10³ L. monocytogenes. Control animals were pretreated with saline. Values are means ± standard error of measurement (n = 4–12); *significantly reduced than corresponding saline control at each time point (p < 0.05).

TABLE 2 Lung inflammation and injury

Time	Treatment	AM (x10^6)	PMN (x10^6)	Albumin (mg/ml)	LDH (U/L)
Day 3	Saline	9.78 ± 0.21	0.04 ± 0.02	0.17 ± 0.01	105 ± 3.6
	0.60 mg Cr	11.00 ± 1.80	2.35 ± 0.69	3.47 ± 0.81	533 ± 86
Day 6	Saline	15.30 ± 0.49	1.33 ± 0.37	0.28 ± 0.03	129 ± 13
	0.60 mg Cr	19.90 ± 2.60	13.60 ± 2.90	1.59 ± 0.25	430 ± 52
Day 10	Saline	16.20 ± 1.40	0.02 ± 0.02	0.17 ± 0.01	123 ± 4.8
	0.60 mg Cr	27.00 ± 1.20	0.44 ± 0.17	0.48 ± 0.05	181 ± 8.9

Note. Values are mean ± standard error of measurement (n = 4–7 animals/group);

*significantly greater than corresponding saline control at each time point (p < 0.05).

FIG. 3 Zymosan-stimulated chemiluminescence of macrophages recovered from rats pre-exposed to 0.60 mg soluble Cr₂Na₂O₇. The Cr sample was intratracheally instilled three days prior to intratracheal inoculation with 5 × 10³ L. monocytogenes. Control animals were pretreated with saline. Values are means ± standard error of measurement (n = 4–7); *significantly greater than corresponding saline control at Day 6 (p < 0.05).

FIG. 4 TNFα measured within the bronchoalveolar lavage fluid (BALF) recovered from rats pre-exposed to 0.60 mg soluble Cr₂Na₂O₇. The Cr sample was intratracheally instilled 3 days prior to intratracheal inoculation with 5 × 10³ L. monocytogenes. Control animals were pretreated with saline. Values are means ± standard error of measurement (n = 4–7); *significantly less than corresponding saline control at Days 3 and 6 (p < 0.05).

FIG. 5 IL-6 measured within the bronchoalveolar lavage fluid (BALF) recovered from rats pre-exposed to 0.60 mg soluble Cr₂Na₂O₇. The Cr sample was intratracheally instilled 3 days prior to intratracheal inoculation with 5 × 10³ L. monocytogenes. Control animals were pretreated with saline. Values are means ± standard error of measurement (n = 4–7); *significantly greater than corresponding saline control at Days 3 and 6 (p < 0.05); n.d. = not detected.

FIG. 6 IL-10 measured within the bronchoalveolar lavage fluid (BALF) recovered from rats pre-exposed to 0.60 mg soluble Cr₂Na₂O₇. The Cr sample was intratracheally instilled 3 days prior to intratracheal inoculation with 5 × 10³ L. monocytogenes. Control animals were pretreated with saline. Values are means ± standard error of measurement (n = 4–7).

FIG. 7 IL-2 measured within the bronchoalveolar lavage fluid (BALF) recovered from rats pre-exposed to 0.60 mg soluble Cr₂Na₂O₇. The Cr sample was intratracheally instilled three days prior to intratracheal inoculation with 5 × 10³ L. monocytogenes. Control animals were pretreated with saline. Values are means ± standard error of measurement (n = 4–7); *significantly less than corresponding saline control at Days 3 and 6 (p < 0.05).

FIG. 8 IL-12p70 measured within the bronchoalveolar lavage fluid (BALF) recovered from rats pre-exposed to 0.60 mg soluble Cr₂Na₂O₇. The Cr sample was intratracheally instilled 3 days prior to intratracheal inoculation with 5 × 10³ L. monocytogenes. Control animals were pretreated with saline. Values are means ± standard error of measurement (n = 4–7); *significantly greater than corresponding saline control at Day 6 (p < 0.05).