Antimicrobial activity of curcumin against Helicobacter pylori isolates from India and during infections in mice

Abstract

Treatment failure is a major cause of concern for the Helicobacter pylori-related gastroduodenal diseases like gastritis, peptic ulcer, and gastric cancer. Curcumin, diferuloylmethane from turmeric, has recently been shown to arrest H. pylori growth. The antibacterial activity of curcumin against 65 clinical isolates of H. pylori in vitro and during protection against H. pylori infection in vivo was examined. The MIC of curcumin ranges from 5 microg/ml to 50 microg/ml, showing its effectiveness in inhibiting H. pylori growth in vitro irrespective of the genetic makeup of the strains. The nucleotide sequences of the aroE genes, encoding shikimate dehydrogenase, against which curcumin seems to act as a noncompetitive inhibitor, from H. pylori strains presenting differential curcumin MICs showed that curcumin-mediated growth inhibition of Indian H. pylori strains may not be always dependent on the shikimate pathway. The antimicrobial effect of curcumin in H. pylori-infected C57BL/6 mice and its efficacy in reducing the gastric damage due to infection were examined histologically. Curcumin showed immense therapeutic potential against H. pylori infection as it was highly effective in eradication of H. pylori from infected mice as well as in restoration of H. pylori-induced gastric damage. This study provides novel insights into the therapeutic effect of curcumin against H. pylori infection, suggesting its potential as an alternative therapy, and opens the way for further studies on identification of novel antimicrobial targets of curcumin.

FIG. 1.

Structure of curcumin.

FIG. 2.

Distribution of curcumin MICs among the Helicobacter pylori strains isolated from Kolkata, India.

FIG. 3.

Amino acid sequences of SDHs encoded by aroE genes from five H. pylori strains were aligned. Sequences from L1675, PG139, PG233, and PG156 are presented in this study. The 26695 sequence was taken from a public database. GenBank accession numbers for sequences presented here are as follows: L1675, EU939307; PG139, EU939304; PG233, EU939305; and PG156, EU939306. Identical nucleotides are indicated by dots. Sequence alignment was performed using the CLUSTALW program within DDBJ.

FIG. 4.

Effect of curcumin on H. pylori viability in H. pylori-infected mice. Lanes 1 (second from the left) and 2 represent the amplification of the vacA middle region using DNA from the mouse-colonizing strains AM1 and SS1 with primers VAG-F and VAG-R (Table 1). Lane 3 represents the amplification of bacterium-specific vacA and the mouse-specific GAPDH gene using DNA isolated from the gastric tissue of control mice. Lanes 4 and 5 represent the amplification of vacA and GAPDH using DNA isolated from the gastric tissue of H. pylori-infected mice after 3 weeks of infection. Lanes 6 and 7 indicate the amplification of vacA and GAPDH using DNA isolated from the gastric tissue of curcumin-treated H. pylori-infected mice. +ve, positive control.

FIG. 5.

Histology of control, H. pylori-infected, and curcumin-treated mouse gastric tissues. Histological sections were stained with hematoxylin and eosin, and photographs were taken at ×10 and ×20 magnifications, respectively. (A to C) Histological appearance of gastric tissues from (A) control mice, (B) mice infected with SS1 for 3 weeks, and (C) mice infected with SS1 and treated with curcumin at 10× magnification. (D to F) Higher-magnification (20×) views of (D) control, (E) SS1-infected, and (F) SS1-infected, curcumin-treated mouse gastric tissues. The gastric mucosal epithelium (black arrows), gastric pits (green stars), gastric glands (green arrows), and inflammatory cell infiltration (black stars) are shown.