Zinc Supplementation Alone Is Effective for Partial Amelioration of Methotrexate-induced Intestinal Damage

Chemotherapeutic agents such as methotrexate (MTX) are commonly used in the treatment of cancer. MTX is an antimetabolite and antifolate drug that targets folate production in rapidly dividing intestinal cells during deoxyribonucleic acid/ribonucleic acid (DNA/RNA) synthesis, thus indiscriminately diminishing enterocyte numbers and disrupting brush-border enzyme activities. The resultant damage leads to a debilitating condition known as intestinal mucositis. New treatment strategies need to be developed for mucositis, as currently no effective treatment exists.

The efficacy of zinc in combination with the probiotic Streptococcus salivarius subsp thermophilus (TH-4) to ameliorate MTX-induced mucositis was investigated.

C57BL/6 mice were randomly assigned to 5 groups: (1) negative control group-saline + saline (SS group); (2) MTX-treated control group-saline + MTX (SM group); (3) MTX-treated intervention group-zinc + TH-4 probiotic + MTX (ZPM group); (4) MTX-treated intervention group-zinc + MTX (ZM group); and (5) MTX-treated intervention group-TH-4 probiotic + MTX (PM group). The mice were gavaged daily from days 1-16 with their respective treatments. From days 6-8, a total of 3 consecutive, daily subcutaneous injections of MTX were used to induce mucositis in the 4 MTX-treated intervention groups, with saline used for the negative controls.

The study was conducted in the gastroenterology unit at the Women's and Children's Health Network, North Adelaide, SA, Australia.

Mice were sacrificed on days 10, 13, and 16. Measurements included body weight, the disease activity index, small-intestine (SI) length and weight, villus height, crypt depth, and mucosal thickness. Also, gut tissues were collected for histological assessments, evaluation of myeloperoxidase (MPO) activity, and analysis of metallothionein (MT) levels.

On days 10 and 13, the treatments received by the ZPM and ZM groups resulted in significantly less jejunal damage (P < .05) compared with the MTX-treated controls (SM) and the PM groups. Zinc treatments in the ZM group induced a 3-fold increase in MT levels, resulting in a significant difference between that group and the SM group (P < .001). The treatments also led to MPO activity that was 31% lower on day 10 compared with the SM and PM groups (P < .01 for each comparison). Mice in the ZM and the ZPM groups showed increased villus height (P < .05) on day 10 compared with the SM and PM groups. Similarly, mucosal thickness was significantly greater in the ZPM and ZM groups on day 10 compared with the SM and PM groups, by 36% (P = .014) and 34% (P = .002), respectively. On day 16, after treatment with zinc in the ZM and ZPM groups, SI weight was 24% lower for the ZM group and 26% lower for the ZPM group compared with the SM group (both P < .001). Crypt depth was increased in the PM group at day 10, resulting in a crypt depth that was 30% greater than that of the SM group (P = .002).

Zinc supplementation alone may be an effective treatment strategy for MTX-induced mucositis, possibly by inducing MT directly.