Based on the present results, we proposed that compromise of autophagy by MIR30B benefits the intracellular H. pylori to evade autophagic clearance through targeting BECN1 and ATG12. The novel model is supported by the following data: (1) autophagy decreased in patients with chronic H. pylori infection, (2) MIR30B was upregulated during H. pylori infection in AGS cell line and human gastric tissues, and (3) compromised autophagy by MIR30B benefited bacterial replication through targeting BECN1 and ATG12 during the H. pylori infection.
It is becoming increasingly recognized that altered autophagy is associated with persistent bacterial infection. For example, Yen-Ting Chu et al. have reported that the autophagy inducer rapamycin enhances the clearance of the H. pylori
They have also reported that H. pylori
usurp the autophagic vesicles as the site for replication, and the autolysosomes after fusion will also degrade the replicating bacteria.33
Therefore, compromised autophagy may benefit the intracellular survival of H. pylori.
Our findings may provide a novel mechanism for elucidating persistent H. pylori
infection. The compromised autophagy by MIR30B
results in a failure to eliminate the intracellular H. pylori
, leading to persistent infection and proliferation of H. pylori
in the host cells.
In our study, H. pylori
infection increased MIR30B
during in vivo and in vitro infections, but there were inconsistent results of autophagy in the two settings. These different results suggest that H. pylori
-mediated autophagic processes may be complex.28
Autophagy plays specific roles in shaping immune system development, fueling host innate and adaptive immune responses, and directly controlling the survival of intracellular microbes as a cell-autonomous innate defense.34
To resist autophagic clearance, intracellular pathogens have evolved to block autophagic microbicidal defense and subvert host autophagic responses for their survival or growth.34
In our cell model, although overexpression of MIR30B
could decrease autophagy through inhibiting the expression of ATG12 and BECN1 (), this adjusting process may lag behind autophagy induced by H. pylori
. Moreover, the part of downregulated autophagy by MIR30B
may be not sufficient to block autophagy induced by H. pylori
. In the study, although MIR30B
mimic was added exogenously, autophagy in H. pylori
infection was still more than that in uninfected group (). Thus, in spite of overexpression of MIR30B
, autophagy still increased during in vitro infection. Given the complexity of H. pylori
in vivo infection, many factors may be involved in autophagy inhibition. As one of the factors, overexpression of MIR30B
may slightly continue to compromise the expression of ATG12 and BECN1 for a long time, leading to subverting host autophagic responses for their survival or growth.
It is of note that upon stimulation with H. pylori
infection, miR-30 family members showed a differential response in which MIR30B
was upregulated whereas MIR30A
was not significantly altered. Although miR-30 family members have a similar sequence, they are expressed by genes localized in different chromosomes.35
It is possible that differential stimuli may affect different genes expression.
Recently, miRNAs have been indicated to play a key role in the regulation of autophagy, such as: MIR30A
was reported to regulate autophagy molecule by targeting BECN1.17
In addition, MIR17/20/93/106
promote hematopoietic cell expansion by targeting sequestosome 1-regulated pathways in mice,18
regulates cardiomyocyte autophagy induced by ischemia-reperfusion through MAP1LC3B-II.19
In this report, we found that MIR30B
is a novel regulator of autophagy by targeting BECN1 and ATG12, which are key autophagy-promoting proteins.
To date, about 10 genes have been experimentally validated in predicted targets of MIR30B
, including CTGF
(connective tissue growth factor), UBE2I
(ubiquitin-conjugating enzyme E2I), ITGB3
(Integrin b3) and TP53
For example, MIR30B
can interact with 3′UTR of EED
and regulate endogenous EED
expression in neural tissues.42
, a major transcriptional regulator of kidney development, was also targeted by MIR30B
Here, we identified BECN1
, which are important genes in regulating autophagy, as novel targets of MIR30B
In summary, our findings provide a novel mechanism in which compromised autophagy by MIR30B benefits the intracellular survival of H. pylori. In addition, these results open a new avenue of research on the potential of miRNAs to modulate autophagy by regulating the expression of key autophagy genes such as BECN1 and ATG12. Although the mechanism of H. pylori infection persistence remains to be determined, this study establishes a basis necessary for future evaluation of the role of MIR30B in H. pylori infections.